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Abstract

Objectives The bony cochlear nerve canal is the space between the fundus of the internal auditory canal and the base of the cochlear modiolus that carries cochlear nerve fibres. This study aimed to determine the distribution of bony labyrinth anomalies and cochlear nerve anomalies in patients with bony cochlear nerve canal and internal auditory canal atresia and stenosis, and then to compare the diameter of the bony cochlear nerve canal and internal auditory canal with cochlear nerve status. Methods The study included 38 sensorineural hearing loss patients (59 ears) in whom the bony cochlear nerve canal diameter at the mid-modiolus was 1.5 mm or less. Atretic and stenotic bony cochlear nerve canals were examined separately, and internal auditory canals with a mid-point diameter of less than 2 mm were considered stenotic. Temporal bone computed tomography and magnetic resonance imaging scans were reviewed to determine cochlear nerve status. Results Cochlear hypoplasia was noted in 44 out of 59 ears (75 per cent) with a bony cochlear nerve canal diameter at the mid-modiolus of 1.5 mm or less. Approximately 33 per cent of ears with bony cochlear nerve canal stenosis also had a stenotic internal auditory canal and 84 per cent had a hypoplastic or aplastic cochlear nerve. All patients with bony cochlear nerve canal atresia had cochlear nerve deficiency. The cochlear nerve was hypoplastic or aplastic when the diameter of the bony cochlear nerve canal was less than 1.5 mm and the diameter of the internal auditory canal was less than 2 mm. Conclusion The cochlear nerve may be aplastic or hypoplastic even if temporal bone computed tomography findings indicate a normal cochlea. If possible, patients scheduled to receive a cochlear implant should undergo both computed tomography and magnetic resonance imaging of the temporal bone. The bony cochlear nerve canal and internal auditory canal are complementary structures, and both should be assessed to determine cochlear nerve status.

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... According to the existing literature, there is a positive correlation between the size of the IAC and the size of the CoN. 3,9 Hypoplastic IAC has been found to be associated with CoN aplasia, while CoN hypoplasia has been described in studies of human temporal bones in association with inner ear malformation and IAC stenosis. 9,10 Congenital sensorineural hearing loss has been shown to be well correlated with IAC stenosis. ...
... The IAC and the bony cochlear nerve canal are said to be complementary structures and are commonly associated with cochlear nerve deficiency. 9 The most common cause of sensorineural hearing loss is said to be a lack of development of CNVIII. 11 Tahir et al. reported that the presence of IAC stenosis on CT images is indicative of CoN aplasia and poor performance with CI surgeries and recommended that the presence of IAC stenosis contraindicate cochlear implantation. ...
... 11 Tahir et al. reported that the presence of IAC stenosis on CT images is indicative of CoN aplasia and poor performance with CI surgeries and recommended that the presence of IAC stenosis contraindicate cochlear implantation. 9 This relationship between the CoN and the IAC supports the concept of using the IAC as a determinate of the path of the CoN since the size, shape and curvature of the IAC inform the shape and path of the CoN. ...
Article
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Person-specific three-dimensional computational modelling plays a vital role in modern-day research of cochlear implants to assist in understanding the neural interface of the cochlea and implanted electrode array. Further improvements are made to these models as more parameters are included. Landmark assessment provides information and is frequently used to register coordinates for model generation as it captures small variations. Objectives The objective of this study is to identify and define landmarks to adequately describe the internal auditory canal for inclusion in three-dimensional computational models of the cochlea and its surrounding structures. Participants Computer tomography scans of live human cochleae were collected in the retrospective period. Descriptive and comparative statistics were used to describe the data obtained from the scans. Results The mean anterior-posterior (AP) diameter at the base of the basal turn, the diameter of the AP at the midpoint of the IAC, and the anterior and posterior length of the internal acoustic canal were measured. 57.14% of the internal acoustic canals observed presented with a cylindrical, 40.48% was funnel-shaped and 2.38 % were bud-shaped. A statistically significant differences were found between the diameters of male and female internal acoustic meatus. Conclusions This paper serves as a reference that provides a set of references for the description of the internal acoustic canal for inclusion in three-dimensional computational reconstruction of the cochlea and surrounding structures.
... Knowledge about the relationship between the IAC and the CoN is particularly important when CI surgery is considered as the CoN plays a vital role in the success of cochlear implantation. According to the existing literature a positive correlation exists between the size of the IAC and the size of the CoN (3,5). A hypoplastic IAC has been found to be associated with CoN aplasia while CoN hypoplasia has been described in studies of human temporal bones in association with inner ear malformation and IAC stenosis (5,6). ...
... According to the existing literature a positive correlation exists between the size of the IAC and the size of the CoN (3,5). A hypoplastic IAC has been found to be associated with CoN aplasia while CoN hypoplasia has been described in studies of human temporal bones in association with inner ear malformation and IAC stenosis (5,6). Congenital sensorineural hearing loss has been proved to be well correlated with IAC stenosis (3,7,8). ...
... The most common cause of sensorineural hearing loss is said to be a lack of development of CNVIII (7). Tahir et al ., reported that the presence of IAC stenosis on CT scans images is indicative of CoN aplasia and poor performance with CI surgeries and recommended that the presence of IAC stenosis contraindicate cochlear implantation (5). This relationship between the CoN and the IAC supports the concept of using the IAC as a determinate of the path of the CoN since the size, shape and curvature of the IAC informs the shape and path the CoN. ...
Preprint
Person-specific three-dimensional computational modelling plays a vital role in modern day research of cochlear implants to assist in understanding the neural interface of the cochlea and implanted electrode array. Further improvements are made to these models as more parameters are included. Landmark assessment provides information and is frequently used to register co-ordinates for model generation as it captures small variations. Objectives: The objective of this study is to identify and define landmarks to describe the internal auditory canal adequately for inclusion in the three-dimensional computational models of the cochlea and its surrounding structures. Participants: Retrospectively collected computer tomography scans of live human cochleae were collected. Descriptive and comparative statistics were used to describe the data obtained from the scans. Results: The mean anterior-posterior (AP) diameter at the base on the basal turn, the AP diameter at the midpoint of the IAC, the anterior and posterior length of the internal acoustic canal were measured. 57.14% of the internal acoustic canals observed presented with a cylindrical, 40.48% was funnel-shaped and 2.38 % was bud-shaped. A statistically significant difference was found between the diameters of the male and female internal acoustic meatii. Conclusion: This paper serves as a reference providing a landmark set for the description of the internal acoustic canal for inclusion in three-dimensional computational reconstruction of the cochlea and surrounding structures.
... A CND characterizes a large portion (35.9%) of our population, most frequently associated with CA stenosis. Both of these anomalies have been previously reported in the literature, although more often individually, or described as a possible feature within more heterogeneous populations 33,37,38 . Unlike most studies describing inner ear anomalies in USNHL patients [38][39][40][41] , we adopted strict exclusion and inclusion criteria to focus on a strictly selected population. ...
... Only 2 cases of aplasia out of 14 CND showed the co-presence of a stenotic CA and an IAC stenosis, and only in 1 case out of 14 CND the stenotic IAC was isolated. As indicated by Tahir et al. 37 , the detection of IAC stenosis alone may be insufficient to indicate a CND: therefore, the CA is www.nature.com/scientificreports/ also required to predict cochlear nerve status. ...
... also required to predict cochlear nerve status. It is worth observing that there is no general agreement regarding how to measure the IAC width 37 , and the CA's diameter can therefore represent a more reliable measure. Further morphological and genetic studies could, in the future, define whether the heterogeneity of the presence of the three anomalies described (CND, CA stenosis, and IAC stenosis) belongs to a continuum of the pathology of the inner ear. ...
Article
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The use of neonatal hearing screening has enabled the identification of congenital unilateral sensorineural hearing loss (USNHL) immediately after birth, and today there are several intervention options available to minimize potential adverse effects of this disease, including cochlear implantation. This study aims to analyze the characteristics of the inner ear of a homogeneous group of congenital non-syndromic USNHL to highlight the features of the inner ear, which can help in clinical, surgical, and rehabilitative decision-making. A retrospective chart review was carried out at a tertiary referral center. Systematic diagnostic work-up and rigorous inclusion–exclusion criteria were applied to 126 children with unilateral hearing impairment, leading to a selection of 39 strictly congenital and non-syndromic USNHL cases, undergoing computed tomography (CT) and magnetic resonance (MR) imaging studies. The frequency and type of malformations of the inner ear in USNHL and unaffected contralateral ears were assessed, with an in-depth analysis of the deficiency of the cochlear nerve (CND), the internal auditory canal (IAC) and the cochlear aperture (CA). Inner ear anomalies were found in 18 out of 39 (46%) of the USNHL patients. In 1 subject, the anomalies were bilateral, and the CND resulted in the predominant identified defect (78% of our abnormal case series), frequently associated with CA stenosis. Only 3 out of 14 children with CND presented stenosis of the IAC. CND and CA stenosis (and to a much lesser extent IAC stenosis) are a frequent association within congenital and non-syndromic USNHL that could represent a distinct pathological entity affecting otherwise healthy infants. In the context of a diagnostic work-up, the evaluation with CT and MRI measurements should take place in a shared decision-making setting with thorough counseling. Both imaging techniques have proven useful in differentiating the cases that will most likely benefit from the cochlear implant, from those with potentially poor implant performance.
... Among other factors, a narrow bony internal auditory canal (IAC) may be associated with poorer hearing performances after David Bächinger and Tabita M. Breitsprecher have equally contributed and shared first authorship. cochlear implantation as a narrow IAC commonly contains a hypoplastic cochlear nerve [1,2,3,4,5]. Furthermore, IAC hypoplasia may be associated with an aberrant facial nerve, which renders the surgical approach to the cochlea more challenging and the risk for intraoperative facial nerve injury is increased [1,6]. ...
... The first definition of a normal IAC was presented in 1964 and together with subsequent studies, a diameter less than 2 mm has become the most widely accepted criterion for a narrow IAC [2,15,16,17]. Currently, there is no broad consensus on how to assess and grade the IAC size. In our previous work, we found that three-dimensional reconstruction and volumetric measurements of temporal bone structures reduce inter-observer differences compared to two-dimensional measurements and may, therefore, help to distinguish normal from abnormal anatomic structures, such as the cochlea or the vestibular aqueduct [18,19,20,21]. ...
Article
Full-text available
Purpose A narrow bony internal auditory canal (IAC) may be associated with a hypoplastic cochlear nerve and poorer hearing performances after cochlear implantation. However, definitions for a narrow IAC vary widely and commonly, qualitative grading or two-dimensional measures are used to characterize a narrow IAC. We aimed to refine the definition of a narrow IAC by determining IAC volume in both control patients and patients with inner ear malformations (IEMs). Methods In this multicentric study, we included high-resolution CT (HRCT) scans of 128 temporal bones (85 with IEMs: cochlear aplasia, n = 11; common cavity, n = 2; cochlear hypoplasia type, n = 19; incomplete partition type I/III, n = 8/8; Mondini malformation, n = 16; enlarged vestibular aqueduct syndrome, n = 19; 45 controls). The IAC diameter was measured in the axial plane and the IAC volume was measured by semi-automatic segmentation and three-dimensional reconstruction. Results In controls, the mean IAC diameter was 5.5 mm (SD 1.1 mm) and the mean IAC volume was 175.3 mm ³ (SD 52.6 mm ³ ). Statistically significant differences in IAC volumes were found in cochlear aplasia (68.3 mm ³ , p < 0.0001), IPI (107.4 mm ³ , p = 0.04), and IPIII (277.5 mm ³ , p = 0.0004 mm ³ ). Inter-rater reliability was higher in IAC volume than in IAC diameter (intraclass correlation coefficient 0.92 vs. 0.77). Conclusions Volumetric measurement of IAC in cases of IEMs reduces measurement variability and may add to classifying IEMs. Since a hypoplastic IAC can be associated with a hypoplastic cochlear nerve and sensorineural hearing loss, radiologic assessment of the IAC is crucial in patients with severe sensorineural hearing loss undergoing cochlear implantation.
... A CND diagnosis was made if one of the following criteria was met: 1) CT of the temporal bone showed that the diameter of the narrowest cross-section of the bony internal auditory canal was less than 2 mm, 7 2) CT of the temporal bone showed cochlear neural tube stenosis (cross-sectional diameter less than 1.5 mm) or undeveloped cochlear neural tube, 7 3) MRI at the midpoint of the internal auditory canal showed that the diameter of the cochlear nerve was smaller than that of the facial nerve, 4) MRI of the internal auditory canal showed no auditory nerve in any cross-section, 8 or 5) the diameter of the vestibular cochlear nerve at the cerebellar pontine angle was less than 1.5 mm or 1.5 times that of the facial nerve. 9 ...
... A CND diagnosis was made if one of the following criteria was met: 1) CT of the temporal bone showed that the diameter of the narrowest cross-section of the bony internal auditory canal was less than 2 mm, 7 2) CT of the temporal bone showed cochlear neural tube stenosis (cross-sectional diameter less than 1.5 mm) or undeveloped cochlear neural tube, 7 3) MRI at the midpoint of the internal auditory canal showed that the diameter of the cochlear nerve was smaller than that of the facial nerve, 4) MRI of the internal auditory canal showed no auditory nerve in any cross-section, 8 or 5) the diameter of the vestibular cochlear nerve at the cerebellar pontine angle was less than 1.5 mm or 1.5 times that of the facial nerve. 9 ...
Article
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Objective: Cochlear nerve deficiency (CND) accounts for 10–19% of hearing loss in children; this study investigated the imaging and audiological features of 25 CND children. Methods: A total of 563 children with an unpassed automatic auditory brainstem response were diagnosed with hearing loss in our department between December 2018 and December 2021, of which, the imaging and audiological features of 25 children (25/563, 4.4%) diagnosed with a CND were reviewed. Results: Twenty-one (21/25, 84.0%) CND children had unilateral deafness, and 4 cases of bilateral deafness. All deaf ears were diagnosed as severe hearing loss due to an auditory brainstem response. CM waves were recorded in 8 cases and DPOAE in 3 cases, suggesting the audiological characteristics of auditory neuropathy spectrum disorders (ANSD). MRI results indicated 23 cases had small cochlear nerves and 2 cases had absent cochlear nerves. No genetic mutations were identified in the 25 CND children. Conclusions: Most CND children had unilateral hearing loss; therefore, high-resolution MRI imaging of the internal auditory canal should be performed to detect the auditory nerve in children with severe hearing loss. Some CND children had characteristics of ANSD.
... While once more commonly diagnosed on CT temporal bone imaging by evaluating stenosis of the cochlear aperture, the cochlear nerve is now most commonly assessed directly by utilizing high-resolution T2-weighted MRI [Glastonbury et al., 2002], which has led to increased rates of diagnosis of CND. Prior studies have shown that the cochlear nerve may be deficient on MRI even when there is a normal cochlear aperture or internal auditory canal (IAC) on CT [Adunka et al., 2006;Tahir et al., 2017;Orzan et al., 2021]. ...
... Importantly, in the present study, the majority of ears with nerve deficiency on MRI demonstrated cochlear aperture stenosis, however, up to 25% demonstrated a grossly normal cochlear aperture on CT, indicating that CT alone is not a reliable method of ruling out nerve deficiency. It is important to note that comparison of past literature assessing the association between cochlear aperture diameter and CND is limited by grossly variable definitions of cochlear aperture stenosis ranging from 1.2 to 1.8 mm [Wilkins et al., 2012;Purcell et al., 2015;Tahir et al., 2017;Lim et al., 2018;Zainol et al., 2020]. While the present study did include 68 ears with available CT imaging, analysis was also limited by the fact that over 75% of ears had MRI imaging alone. ...
Article
Introduction: The rates of cochlear nerve abnormalities and cochlear malformations in pediatric unilateral hearing loss (UHL) are conflicting in the literature, with important implications on management. The aim of this study was to investigate the incidence of cochlear nerve deficiency (CND) in pediatric subjects with UHL or asymmetric hearing loss (AHL). Methods: A retrospective chart review of pediatric subjects <18 years of age evaluated for UHL or AHL with fine-cut heavily T2-weighted magnetic resonance imaging (MRI) between January 2014 and October 2019 (n = 291) at a tertiary referral center was conducted. MRI brain and computed tomography temporal bone were reviewed for the presence of inner ear malformations and/or CND. Status of the ipsilateral cochlear nerve and inner ear was evaluated. Pure tone average (PTA) at 500, 1,000 and 2,000 Hz was assessed. Results: 204 subjects with UHL and 87 subjects with AHL were included. CND (aplasia or hypoplasia) was demonstrated in 61 pediatric subjects with UHL (29.9%) and 10 with AHL (11.5%). Ipsilateral cochlear malformations were noted in 25 subjects with UHL (12.3%) and 11 with AHL (12.6%), and ipsilateral vestibular malformations in 23 (11.3%) and 12 (13.8%) ears, respectively. Median PTA was statistically significantly higher in ears with CND (98.33) than ears with normal nerves (90.84). Discussion/conclusion: Imaging demonstrated a high incidence of inner ear malformations, particularly CND, in pediatric subjects with UHL. Auditory findings indicated CND cannot be ruled out by thresholds alone as some CND ears did demonstrate measurable hearing. Radiologic evaluation by MRI should be performed in all patients within this population to guide counseling and management of hearing loss based on etiology, with implications on candidacy for cochlear implantation.
... The causes of hearing loss in children can be different. Deafness can be congenital or acquired, and it is estimated that even 20% of all cases of congenital sensorineural hearing loss are due to inner ear abnormalities involving the bony labyrinth [1]. With the introduction of universal neonatal hearing screening, deafness can be diagnosed in the first months of life and this allows early treatment and minimization of the negative implications of this anomaly. ...
... The diameter of the cochlear nerve canal was measured as a distance between the inner boundary of its bony walls in the middle of an axial section at the level of the base of the modulus. The BCNC is located between the bottom of the internal auditory canal (IAC) and the base of the cochlea and contains the nerve fibers that run from the spiral ganglion to the cochlear nerve [1] ( Figure 1). Therefore, a narrow BCNC probably indicates an anatomical or functional defect of the cochlear nerve due to which the width of the cochlear nerve canal seems to be a reliable radiological marker of the presence and status of the cochlear nerve. ...
Article
Introduction: The aim of this study was to evaluate the width of the bony cochlear nerve canal (BCNC) in children with congenital sensorineural hearing loss (SNHL) and "normal" findings on thin section temporal bone CT. Material and methods: The width of the BCNC was retrospectively evaluated in two groups of patients. The study group included 11 children (22 bone canals) aged 2-12 years, with congenital, bilateral SNHL who underwent cochlear implantation (CI) from July to December 2019 and no abnormalities of the inner ear were detected on their preoperative CT scans. Eleven patients (22 bone canals), aged 3-10 years, in whom no sensorineural hearing loss had been diagnosed were taken as controls and CT scan of the temporal bone was performed for another reason - suspected acute mastoiditis, chronic otitis media, or perforation of the tympanic membrane. Axial sections of their CT scans were used to measure the width of the BCNC. Results: BCNC width values in patients with bilateral, profound sensorineural hearing loss ranged from 1.0 to 2.3 mm and the mean value was 1.5±0.3 mm. In patients with normal hearing, the values for the canal width were higher, with mean value of 2.1±0.3 mm. Conclusion: The results obtained showed that the width of the BCNC in children with bilateral, profound sensorineural hearing impairment was significantly smaller than in the control group with normal hearing for p <0.05 (t-test=6.62912, p=0.000000). Keywords: bony cochlear nerve canal, children, congenital sensorineural hearing loss
... 14 Therefore, preoperative computed tomography and magnetic resonance imaging exams, in addition to adequate hearing evaluation, are essential tools to anticipate those potential surgical pitfalls and increase the likelihood of good functional results. 1,14 In our study, clinical data from the donors revealed that the majority of patients who had inner ear malformations were syndromic or had several other associated malformations. Those results are consistent with the literature: it has been demonstrated that inner ear malformations in isolation are uncommon. ...
... Therefore, it seems that CH2 is favorable for cochlear implantation surgery. 1,14,25 Yet, we identified that those donors would have a conceivable risk of gusher, in view of the high frequency of partial or complete modiolar defects observed in our HTBs with CH2. 26 The mastoid and the middle ear were also hypodeveloped in all HTBs, and the course of the facial nerve was also abnormal in 80% of the bones. Considering those middle ear abnormalities, our observations suggest that the conventional facial recess approach for cochlear implantation in those patients would bear high chances of facial nerve injury. ...
Article
Hypothesis: The presence of bony inner ear malformations may associate with a number of anatomical abnormalities affecting the middle ear structures. Those malformations may create pitfalls and complications for cochlear implantation. Background: Inner ear malformations associate with varying degrees of hearing loss, and frequently require cochlear implantation for hearing rehabilitation. Therefore, the abnormalities affecting the middle- and inner-ear structures may increase the risk of surgical complications. Methods: We examined 38 human temporal bones from donors with bony inner ear malformations. Using light microscopy, we analyzed the presence of abnormalities in the structures of the middle- and inner-ear. Results: Our collection comprises of 38 specimens with inner-ear malformations (cochlear aplasia, n = 3; cochlear hypoplasia, n = 30; incomplete partition, n = 3; isolated vestibular malformation, n = 2). The anatomy of the middle ear was abnormal in most temporal bones with cochlear aplasia, cochlear hypoplasia, and incomplete partition type I (40%–100%). Some of those abnormalities (hypoplastic or obliterated mastoid, 55.2%; aplastic or obliterated round window, 71.0%; aberrant course of the facial nerve, 36.8%) may hinder the access to the round window using the conventional facial recess approach for cochlear implantation. The cochlear nerve and associated bony structures (internal auditory canal and bony canal for cochlear nerve) were normal in 71.0% of all temporal bones with inner ear malformations. Conclusion: Each different type of malformation may create specific surgical challenges to surgeons. Comprehensive preoperative imaging is fundamental toward the surgical success of cochlear implants in patients with malformations. Alternatives to circumvent those middle- and inner-ear abnormalities and potential complications are further discussed.
... The number of spiral and Scarpa ganglion cells was analyzed using the methodology proposed by Otte et al. (2) and Richter (3), and the results were compared with normative data (2,4). Using a computer software (NIS-elements; Nikon Co., Tokyo, Japan), we measured the diameter and longitudinal length of the internal auditory canal (IAC), and the diameter of the bony cochlear nerve canal (BCNC) (5,6); those were considered narrowed when the maximum diameter at any portion was less than 2.0 mm (IAC) or 1.5 mm (BCNC) (6). The vestibular aqueduct was considered enlarged when the diameter at the midpoint equaled or exceeded 0.9 mm (7). ...
... In the TB with cochlear abnormalities (left ear), we observed that the modiolus was hypoplastic, and the BCNC and IAC were narrowed, and those associated with the absence of cochlear nerve and decreased number of spiral and Scarpa ganglion cells. Similarly to our findings, it has been observed that the diameter of the IAC and BCNC correlates negatively with the cochlear nerve function, and it may also associate with hypoplasia or aplasia of the cochlear nerve (6). ...
... The narrowed IAC is a radiological (HRCT) term introduced by Valvassori, corresponding to a less than 2 mm diameter in the axial plane with hypoplastic or absent CVN [13][14][15]; therefore, we suggested the use of the "near" narrowed IAC (NNIAC), which is consistent with preserved morphometric characteristics of IAC on MRI [12]. Since axial cuts seemed to be less discriminating than coronal cuts, the NNIAC threshold values of 3.3 mm (in HRCT) and 2.9 mm (in MRI) were used in the present study [12]. ...
Article
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Background/Objectives: Objective: To discuss therapeutic outcomes in patients with symptomatic near-narrow internal auditory canal (NNIAC). Methods: We retrospectively analyzed the records of 26 symptomatic patients diagnosed with NNIAC, who had been treated with anti-epileptic drugs. In addition to clinical and radiological data, we recorded I–III latencies of auditory brainstem responses prior to and after medical therapy. Results: Among a total of 48 patients with NNIAC, 26 patients were included. Oxcarbazepine, Gabapentin, and Lamotrigine were prescribed among 19 (73%) patients, 6 (23%) patients, and 1 patient (4%), respectively. After treatment, 24 (92.3%) patients described improvement of vestibular symptoms, and 16 (76.2%) reported improvement of auditory symptoms. After treatment with antiepileptic drugs, ipsilateral IPL I-III latencies decreased (less than 2.3 ms) in 16 (84.2%) patients (23 ears out of 42). Conclusions: A low dose of anti-epileptic monotherapy for NNIAC could be effective over the long term and is generally well-tolerated. Further studies are needed to provide more solid evidence of the efficacy and safety of anti-epileptic drugs on a larger number of patients with NNIAC.
... Theo nghiên cứu của Nguyễn Phương Lan [6] thì 100% bất sản thần kinh ốc tai ở hố ốc tai tịt, 84.5% bất sản thần kinh ốc tai ở hố ốc tai hẹp. Theo nghiên cứu của Adunka [7] và Tahir [8] cũng cho kết quả 100% hố ốc tai tịt có bất sản thần kinh ốc tai. Nghiên cứu của chúng tôi cho thấy tỷ lệ hẹp và tịt hố ốc tai, bất sản thần kinh ốc tai đều chiếm tỷ lệ cao. ...
Article
Mục đích: mô tả đặc điểm hình ảnh cắt lớp vi tính (CLVT) và cộng hưởng từ (CHT) của các type thiểu sản ốc tai. Phương pháp: dị dạng tai trong và bất thường dây thần kinh ốc tai (TKOT) được đánh giá trên CLVT độ phân giải cao và chuỗi xung T2 3D gradient-echo độ phân giải cao CHT. Kết quả: nghiên cứu gồm 24 bệnh nhân (BN) với 45 tai trong đó có 10 tai dị dạng type I, 14 tai dị dạng type II, 14 tai dị dạng type III, 7 tai dị dạng type IV. Kích thước trung bình vòng đáy ốc tai của các type II, III và IV đều thiểu sản. 68.9% các trường hợp có hẹp và tịt hố ốc tai, 60% các trường hợp có bất sản TKOT. 100% các type II, III và IV có thiểu sản trụ ốc tai. Hẹp và bất sản cửa sổ tròn chiếm 66.7% các trường hợp. Kết luận: kích thước trung bình chiều ngang và chiều cao vòng đáy ốc tai ở các type II, III, IV đều thiểu sản. Tịt, hẹp hố ốc tai và bất sản thần kinh ốc tai chiếm tỷ lệ cao, trong đó tịt và hẹp hố ốc tai hay gặp ở thiểu sản type III, bất sản TKOT gặp ở nhiều ở nhóm thiểu sản type I. Trụ ốc tai thiểu sản ở tất cả các trường hợp thiểu sản type II, III và IV; bất sản ở Type I. Bất thường cửa sổ tròn như hẹp, không có cửa sổ tròn chiếm tỷ lệ cao, gây khó khăn cho phẫu thuật đặt điện cực ốc tai.
... Internal auditory canal stenosis has been associated with other abnormalities particularly hypoplasia or aplasia of the cochlear nerve and stenosis of the bony cochlear nerve canal. 6 Since all of these factors individually and collectively have an impact on hearing rehabilitation with external hearing devices and cochlear implants, identifying these conditions using the appropriate imaging study becomes necessary. As such, a clinician must accept the reality that both CT and MRI studies may be warranted in an individual patient, as these studies provide complementary information on the status of the hearing pathway. ...
Article
Full-text available
A 3-year-old boy underwent evaluation for possible cochlear implantation. He had failed a neonatal otoacoustic emission (OAE) hearing screen. A combined auditory brainstem response/auditory steady-state response (ABR/ASSR) test battery confirmed the presence of a severe hearing loss on the right and a profound hearing loss on the left. No Joint Committee on Infant Hearing (JCIH) risk factors for early childhood hearing loss1 were identified. Rehabilitation via hearing aid amplification and auditory-verbal speech therapy was unsuccessful. Computerized tomographic (CT) imaging of the temporal bone was performed to identify the presence of any inner ear abnormalities. No abnormalities of the cochlea, vestibule and semicircular canals on both sides were identified by the radiologist. The internal auditory canals were described as “fairly symmetrical without widening”, and the study was officially reported as an “unremarkable study of the temporal bones”. Independent review of the CT imaging revealed the presence of seemingly narrow internal auditory canals (IAC) on both sides. (Figure1A) The width of the IACs on the axial plane were measured by drawing a perpendicular line starting from the posterior wall of the IAC, 2 mm inside the posterior lip of the internal auditory meatus, and ending on the anterior canal wall, as described by McClay et al.2 Measurements taken utilizing the length measurement tool in the DICOM imaging software (RadiAnt DICOM Viewer, Version 2024.1, Medixant) indicated an IAC width of 1.78 mm on the right (with severe hearing loss) and 1.37 mm on the left (with profound hearing loss). (Figure 1B) These measurements confirmed the presence of bilateral internal auditory canal stenosis, a diagnosis defined by a canal of 2 mm or less on highresolution CT.3
... Valvassori first reported the normal dimensions of the IAC [32,33]. A diameter of less than 2 mm in the axial plane is the most accepted criterion for evoking a narrowed IAC [34][35][36][37][38][39]. Since a narrow IAC implies hypoplastic or absent CVN, we suggest the notion of a "nearly narrowed IAC" (NNIAC). ...
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Introduction: Vestibular Paroxysmia (VP) refers to short attacks of vertigo, spontaneous or triggered by head movements, and implies the presence of a compressive vascular loop in contact with the cochleovestibular nerve (CVN). Classically, a narrowed internal auditory canal (IAC) corresponds to a diameter of less than 2 mm on CT, usually associated with a hypoplastic CVN on MRI. The aim of this study was to discuss a distinct clinical entity mimicking VP in relation to a "near"-narrowed IAC (NNIAC) and to propose radiological criteria for its diagnosis. Methods: Radiological measurements of the IAC were compared between three groups: the study group (SG, subjects with a clinical presentation suggestive of VP, but whose MRI of the inner ear and pontocerebellar angle excluded a compressive vascular loop) and two control groups (adult and children) with normal vestibular evaluations and no history of vertigo. Results: 59 subjects (18 M and 41 F) were included in the SG. The main symptoms of NNIAC were positional vertigo, exercise- or rapid head movements-induced vertigo, and dizziness. The statistical analysis in the study group showed that the threshold values for diagnosis were 3.3 mm (in tomodensitometry) and 2.9 mm (in MRI) in coronal sections of IAC. Although a significantly lower mean value for axial IAC diameter was found in SG compared with controls, the statistics did not reveal a threshold due to the large inter-individual variations in IAC measurements in normal subjects. There was no significant difference in IAC diameter between the adult and pediatric controls. Conclusions: In the present study, we report a new anatomopathological condition that appears to be responsible for a clinical picture very similar-but not identical-to VP in association with the presence of an NNIAC. The diagnosis requires a careful analysis of the IAC's shape and diameters in both axial and coronal planes.
... Cochleovestibular anomalies are found in up to 35% of pediatric patients undergoing evaluation for CI [12]. Furthermore, the cochlear nerve may be aplastic or hypoplastic in the presence of normal appearing temporal bone on HRCT due to independent development of the organ of Corti and the cochlear nerve [15,16]. Thus, the complementary use of both imaging modalities may be beneficial in pediatric patients [12]. ...
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Purpose of the Review Cochlear implantation is an effective treatment for severe to profound hearing loss in children and adults. Computed tomography, radiography, and magnetic resonance imaging are essential throughout the cochlear implantation process. The purpose of this article is to provide a comprehensive review of the uses of imaging at each stage of cochlear implantation, highlighting clinically relevant points for the radiologist as well as areas of ongoing exploration. Recent Findings The newer, evolving nature of the field presents many rising opportunities for collective imaging-based research. For example, standardization and improvement in imaging indications and protocols, as well as methods of cochlear duct length measurement and reporting have potential to significantly contribute to refinements in cochlear implant placement and detection of complications. Summary In collaboration with audiologist and otolaryngologists, radiologists serve an important role in the initial work up of cochlear implant candidates, pre-operative surgical planning, and post-operative monitoring.
... However, 37 of the 48 cochlear anomalies in their study were IP type 2 cases. Of 38 patients with a stenotic CNC in a study, 6 had IP type 1, and 1 had IP type 2 (18). The CNCW was measured below 1.5 mm in just three ears in our study. ...
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Introduction:Incomplete partition (IP) type and accompanying cochlear nerve (CN) anomalies affect the patient’s management. We revealed the cochlear nerve area (CNA), cochlear nerve canal width (CNCW), and inner auditory canal width (IACW) of IP types.Methods:We retrospectively scanned patients with IP. There were 88 IP ears (26 IP type 1, 54 IP type 2, 8 IP type 3) and 54 controls. The CNCW and IACW were measured in axial temporal computed tomography sections. The CNA and facial nerve area (FNA) were measured in the distal IAC on the sagittal-oblique plane of 3D constructive interference steady-state T2-weighted magnetic resonance images.Results:CNA and CNA/FNA values for each IP type differed significantly compared with the control group. However, the CNCW and IACW values did not differ significantly. The CNA was the least in IP 1 cases. Five CN aplasia were detected, and all were associated with IP type 1 anomaly (3.5% of all, 5.6% of IP types, and 19.2% of IP type 1 cases). CN hypoplasia was observed in 10 IP type 1 (38.5% of IP 1), 6 IP type 2 (6.8% of IP type 2), and 1 IP type 3 (12.5% of IP type 3) ears. None of the CN hypoplasia had a CNC hypoplasia.Conclusion:CN aplasia and hypoplasia most frequently accompanied with IP type 1 in our study. Therefore, they need an extra interest in CN evaluation. CNCW and IACW are not very useful in predicting CN dysplasia in IP cases.
... According to Kang et al. (7), in normalhearing ears, there is no relation between CN size and age. The CN is ovoid rather than round, i.e., its vertical and horizontal diameters are not equal (16,17). CN morphometry is well measured by MRI with CISS sequence) on parasagittal images of the IAC, in which the CN is optimally visualized (18)(19)(20). ...
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Introduction:To investigate the relationship between morphometric variants of the cochlear nerve (CN) and the hearing level. To investigate the confounding effects of age, sex, and audiometric variables on the relationship between CN morphometrics and hearing loss, if present.Methods:Audiological data and magnetic resonance imaging findings of 127 patients with asymmetrical sensorineural hearing loss (ASNHL) were reviewed retrospectively. According to pure tone average (PTA) frequencies of each ear, difference above 25 dB were accepted as ASNHL. The vertical (Vd) and horizontal diameters (Hd) and the cross-sectional area (CSA) of the CN were measured.Results:The difference in CSA and Vd between ears showed a negative correlation with age. The mean CSA was 1.57 in AE and 1.60 in NE. Mean Hd was 1.00 in AE and 1.00 NE. Mean Vd was 1.40 in AE and 1.50 in NE. There was no correlation between the difference ratios of thresholds and CN diameter parameters. There was no significant correlation of CSA, Vd, and Hd with PTA thresholds at each frequency.Conclusion:Aging is associated with losses in Vd diameter and CSA. The degree of hearing loss was not correlated with the morphometric features of the CN. The morphometry of the CN should be interpreted together with the etiology of hearing loss.
... In about one third of cases of stenotic bony cochlear nerve canal, there is also a stenotic internal auditory canal with a diameter at the midpoint of the canal smaller than 2.5 mm. These patients frequently show a hypoplastic or aplastic cochlear nerve, which impedes clinical outcomes [38]. Hypoplasia of the vestibulocochlear nerve may be seen in cochlear aplasia, complete aplasia of the semicircular canals, severe cochlear hypoplasia, common cavity, incomplete partition type 1, and mild cochlear hypoplasia, with decreasing degrees of correlation [39]. ...
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Abstract Cochlear implants are increasingly used to treat sensorineural hearing disorders in both children and adults. Pre-operative computed tomography and magnetic resonance imaging play a pivotal role in patient selection, to rule out findings that preclude surgery or identify conditions which may have an impact on the surgical procedure. The post-operative position of the electrode array within the cochlea can be reliably identified using cone-beam computed tomography. Recognition of scalar dislocation, cochlear dislocation, electrode fold, and malposition of the electrode array may have important consequences for the patient such as revision surgery or adapted fitting.
... CT and MR imaging of the temporal bone should be performed prior to cochlear implantation to assess the osseous anatomy, fluid spaces, and integrity of the VCN. The absence of a VCN has generally been considered a relative contraindication to cochlear implants [12] . Auditory brainstem implantation may represent a therapeutic alternative for these patients. ...
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We present a case of an otherwise healthy 20-month-old with congenital sensorineural hearing loss. CT and MR imaging demonstrated bilateral asymmetrically severe hypoplasia of the internal auditory canals and vestibulocochlear nerves. Additional developmental inner ear anomalies were present in this patient, including unilateral semicircular canal hypoplasia and suspected bilateral cochlear hypoplasia. The patient retained normal facial nerve function bilaterally. We highlight the current research and understanding of congenital IAC abnormalities.
... The bony cochlear nerve canal (i.e., the CA) was measured at its mid-point at the mid-modiolar level on the axial images and evaluated as normal, stenotic, or atretic. Based on the current literature, a width of < 1.5 mm was accepted as the cutoff value for a diagnosis of CA stenosis [Purcell et al., 2015;Tahir et al., 2017]. ...
Article
Background: Cochlear nerve deficiency is a general term used to describe both cochlear nerve hypoplasia (CNH) and cochlear nerve aplasia. Although these two conditions can have similar results on audiological evaluation, CNH yields more variation in audiological tests. Objectives: To describe the audiological characteristics of the CNH cases in our series in relation to radiological findings. Methods: We reviewed the medical charts, audiological findings, and radiological findings on cases with CNH. We included cases with CNH in one ear or both ears. Out of 90 subjects with CNH, we included a total of 40 individuals (21 women and 19 men; 49 ears) in the current study. We reviewed and analyzed the participants' audiological test results according to the radiological findings. Results: Cases with CNH showed variations according to the cochlear structure. There were 13 normal cochleae, 4 with incomplete partition type I, and 32 with cochlear hypoplasia. The accompanying cochlear apertures also showed variation: 17 were normal, 28 stenotic, and 4 aplastic cochlear apertures. The subjects displayed hearing loss ranging from moderate to profound; furthermore, 4 subjects had no response to sound whatsoever. The degree of hearing loss was not statistically significantly different with regard to the presence or absence of cochlear malformation with CNH (p > 0.005). We observed both sensorineural hearing loss and mixed-type hearing loss among the CNH cases. Conclusions: CNH is the presence of a cochlear nerve that is smaller in diameter than the facial nerve. It can be accompanied with other associated inner ear malformations of different degrees of severity. We observed degrees of hearing loss ranging from moderate to profound.
... Besides that, McClay et al. detected 18% cochlear nerve absence or deficiency which could be mostly identified by MRI of internal auditory canal [19]. Tahir et al. detected that MRI can show aplastic or hypoplastic nerve even if the cochlear structure is normal and they suggested both HRCT and MRI to evaluate cochlear nerve patency [20]. We changed the surgical planning of side in pediatric candidates because of cochleovestibular anomaly in six children, narrow internal acoustic meatus in one child and cochlear nerve hypoplasia in two children. ...
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Purpose There is no guideline or consensus on preoperative radiologic imaging modality despite the fact that it has a vital importance in appropriate candidacy selection of cochlear implantation. We aimed to find out the role of high-resolution computed tomography (HRCT) and magnetic resonance imaging (MRI) on surgical planning, intraoperative technique in cochlear implant candidates. Methods The clinical charts, imagings, and operative reports of patients who underwent cochlear implant surgery at a tertiary institution were retrospectively examined. Results 611 patients (503 children and 108 adult) were enrolled into the study. We found 11 different pathologies in MRI which could not be seen in HRCT. However, we decided the side of surgery according to MRI in only three of them in which the pathology was cochlear nerve hypoplasia. Two patients with cochlear nerve hypoplasia were children with prelingual deafness and one was adult with perilingual deafness. Moreover, we changed the surgical planning of side according to both imaging modalities in nine patients. Seven of them were children and two were adult. One of these adults had cochlear anomaly, and another had bilateral temporal bone fracture. Conclusions We suggest both imaging modalities in pediatric candidates. However, in adults, we think that superiority of either imaging modalities is still contradictive. We had only three adult patients and the decision of the side of surgery was made according to MRI in one of them and to both imaging modalities in the other two adults.
Article
Background: Deaf children with cochlear nerve canal stenosis (CNCs) are always considered poor candidates for cochlear implantation. Objectives: To investigate the function of the peripheral auditory pathway in deaf children with CNCs, as revealed by the electrically evoked auditory brainstem response (EABR), and postoperative cochlear implants (CIs) outcomes. Materials and methods: Thirteen children with CNCs and 13 children with no inner ear malformations (IEMs) who received CIs were recruited. The EABR evoked by electrical stimulation from the CI electrode was recorded. Postoperative CI outcomes were assessed using Categories of Auditory Performance (CAP) and Speech Intelligibility Rate (SIR). Results: Compared with children with no IEMs, children with CNCs showed lower EABR extraction rates, higher thresholds, a longer wave V (eV) latency and lower CAP and SIR scores. The auditory and speech performance was positively correlated with the diameter of the cochlear nerve canal and the number of channels showing wave III (eIII) and eV in children with CNCs. Conclusions and significance: The physiological function of the peripheral auditory pathway in children with CNCs is poorer than that in children with no IEMs. Postoperative auditory and speech abilities may depend on the severity of cochlear nerve malformation and auditory conduction function.
Article
Objective Cochlear nerve deficiency (CND) is a common radiologic finding among unilateral sensorineural hearing loss (USNHL) patients. It is generally detected with magnetic resonance imaging (MRI), which is associated with higher cost, less availability, and possible need for sedation. Therefore, identifying computed tomography (CT) findings, such as cochlear aperture stenosis (CAS), that can reliably predict CND is valuable. Our study aimed to determine the prevalence of CND in pediatric patients with CT‐diagnosed CAS. Study Design Retrospective study. Setting Tertiary care center. Methods We included pediatric patients diagnosed with CAS on temporal bone CT and with available temporal bone MRI. For each patient, an otolaryngologist and a pediatric neuroradiologist measured the cochlear aperture width on CT to confirm CAS (cochlear aperture < 1.4 mm) and assessed the status of the cochlear nerve on MRI. Results Fifty‐five patients, representing 65 ears, had CAS on CT measurement. Median cochlear aperture width in CAS ears was 0.70 mm (interquartile range [IQR]: 0.40‐1.05 mm) versus 2.00 mm in non‐CAS ears (IQR: 1.80‐2.30 mm, P < .001). CND was found in 98.5% (n = 64/65) of CAS ears, while a normal cochlear nerve was found in 1.5% (n = 1/65) of CAS ears. Conclusion CND is highly prevalent among pediatric patients with CAS. This suggests that MRI may not be needed to assess for CND in USNHL patients with CAS, as initial CT may provide sufficient information to determine cochlear implant candidacy. We recommend thoughtful shared decision‐making with parents of USNHL patients when determining whether to pursue MRI in the setting of a CAS diagnosis.
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Objectives The aim was to describe the spectrum of inner ear malformations in CHARGE syndrome and propose a Computed Tomography (CT) detailed scan evaluation methodology. The secondary aim was to correlate the CT findings with hearing thresholds. Methods Twenty ears of ten patients diagnosed with CHARGE syndrome were subjected to CT analysis focusing on the inner ear and internal acoustic canal. The protocol used is presented in detail. ASSR results were analyzed and correlated with inner ear malformations. Results Cochlear hypoplasia type III was the most common malformation found in 12 ears (60%). Cochlear hypoplasia type II, aplasia with a dilated vestibule, and rudimentary otocyst were also identified. In 20%, no cochlear anomaly was found. The lateral Semicircular Canal (SCC) absence affected 100% of ears, the absence of the posterior SCC 95%, and the superior SCC 65%. Better development of cochlea structures and IAC correlated significantly with the lower hearing thresholds. Conclusion This study demonstrated that rudimentary SCC or a complete absence of these SCCs was universally observed in all patients diagnosed with CHARGE syndrome. This finding supports the idea that inner ear anomalies are a hallmark feature of the CHARGE, contributing to its distinct clinical profile. The presence of inner ear malformations has substantial clinical implications. Audiological assessments are crucial for CHARGE syndrome, as hearing loss is common. Early detection of these malformations can guide appropriate interventions, such as hearing aids or cochlear implants, which may significantly improve developmental outcomes and communication for affected individuals. Recognizing inner ear malformations as a diagnostic criterion presents implications beyond clinical diagnosis. A better understanding of these malformations can advance the knowledge of CHARGE pathophysiology. It may also help guide future research into targeted therapies to mitigate the impact of inner ear anomalies on hearing and balance function. Level of evidence 4.
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Objective The aim of this study is to evaluate the relationship between the cochlear nerve and the anatomical structures of the cochlea and internal acoustic canal in patients with congenital hearing loss. Materials and Methods Temporal tomography and magnetic resonance images of 44 patients (88 ears) with non-syndromic congenital hearing loss were retrospectively analyzed between 2018 and 2021. Patients were divided into 2 groups according to cochlear nerve hypoplasia. Cochlear nerve canal width, cochlear basal/middle turn widths, and internal auditory canal widths were examined. Results Cochlear nerve hypoplasia was detected in 18.2% (n = 16) of the patients and all of the patients with cochlear nerve hypoplasia had severe hearing loss. A statistically significant difference was found between the structures’ widths in patients with and without cochlear nerve hypoplasia, in cochlear nerve canal and coronal width of the internal auditory canal. When stenosis is accepted as <1.4 mm for cochlear nerve canal and <3.80 mm for coronal width of the internal auditory canal, cochlear nerve hypoplasia differs statistically between the groups in measurements (respectively; P < .001, P = .018). Conclusions In patients with sensorineural hearing loss, cochlear nerve hypoplasia may accompany. Anatomical structures are important in predicting cochlear nerve hypoplasia from temporal computed tomography. Cochlear nerve hypoplasia should be suspected if the cochlear nerve canal and coronal width of the internal auditory canal are less than 1.4 mm and 3.8 mm, respectively, on temporal computed tomography.
Article
Cochlear Implantation (CI) is a well-accepted treatment for severe-to-profound sensorineural hearing loss, refractory to conventional hearing amplification. Pre-operative Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) play pivotal roles in patient selection to rule out findings that preclude surgery or identify conditions that may impact the surgical procedure. A prospective study was carried out in a tertiary care center over three years, from January 2020 to January 2023. One hundred and ninety (380 ears) patients’ High-Resolution Computed Tomography (HRCT) studies of the temporal bone and MRI scans of the auditory pathways were analyzed. A reporting format was followed which was devised by a team of senior implant surgeons and senior neuro-radiologists. Our study aims to provide a comprehensive radiologic protocol for CI candidacy including normative data for the essential morphometrics in the Indian setting.
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Objectives : The presence of a functional cochlear nerve is a key issue in the preoperative evaluation of pediatric candidates for cochlear implants. Correlations between cochlear nerve deficiency (CND) and bony abnormalities of the labyrinth or bony canal of the cochlear nerve are not yet well understood. The aim of this study was to determine whether the width of the bony cochlear canal (BCNC) can serve as a reliable predictive factor for the existence of a CND. Materials and methods : A total of 11 children with a confirmed diagnosis of prelingual, severe sensorineural hearing loss were included in this study. In all patients, indication for CI was confirmed and according to the preoperative protocol, high-resolution CT and MR were performed. Reconstructions at a distance of 0.6 mm of the axial plane and images from the HRCT of temporal bones were used for measuring the width of the BCNC. The cochlear nerves were evaluated on axial and sagittal – oblique T2 – MRI images and classified as normal, hypoplastic or aplastic. Two factors were reviewed retrospectively: the presence of inner ear anomalies and the relationship between BCNC stenosis and the existence of CND. Results : From a total of 22 temporal bones analyzed (22 ears in 11 patients), inner ear malformations were detected in 6 ears from 3 patients (27.27%). All three children had a bilateral malformation, in one it was Michel deformity and in two it was IP2 (incomplete partition 2). The BCNC diameter ranged from 0.1mm to 2.33mm with a mean value of 1.46±0.6mm. CND was recorded in 4 of 22 ears and all were associated with stenosis of the BCNC. In a total of three ears with a stenotic canal, we obtained a normal finding for the cochlear nerve on MR. Conclusion : Children with BCNC stenosis have a high incidence of CND. A narrowed BCNC on CT can be an indicator for the selection of children with sensorineural hearing loss who will need to be additionally referred for MRI in order to definitively assess the status of the cochlear nerve.
Article
Purpose: This study investigated the correlation between the diameter of the bony cochlear nerve canal (BCNC), as determined by Temporal bone CT, and MRI findings of cochlear nerves (CN) in children with sensorineural hearing loss (SNHL). Materials and methods: A prospective study design was followed. Radiological data (Temporal bone CT and MRI) of fifty children with sensorineural hearing loss (age <18 y) were included in the study. All patients (100 ears) underwent routine MRI protocol in addition to 3D CISS (3-D constructive interference in steady state). Results: Based on CT findings, the BCNC was classified according to its diameter into three groups; group 1 (<1.4 mm), group 2 (1.4-2.0 mm), and group 3 (>2.0 mm). A significant difference between the three groups at degrees of SNHL (p < 0.001) was observed. Significant difference (p < 0.001) was also observed in the mean level of pure tone audiometry (PTA) average in group 1 compared to group 2. The CN was absent in 20 ears of group 1 CT results (29%), CN hypoplasia was noticed in 40 ears of group 1 CT (58%). However, CN was present in 9 ears of group 1 CT (13%), while in group 2 and 3, CN was present in 100% of the cases (27, and 4 ears, respectively, p < 0.001). Conclusions: MRI and CT imaging are valuable in the diagnosis of SNHL in children. Moreover, with BCNC stenosis, there was a high probability of CN aplasia or hypoplasia.
Chapter
The bony cochlear nerve canal (BCNC) is a tiny canal that transmits the cochlear nerve, which can be clearly seen by high-resolution computed tomography or cone beam computed tomography. The size of the BCNC can serve as a reliable marker for cochlear nerve deficiency. A BCNC width of <1.4 mm or a decrease in its width compared to the contralateral normal BCNC may indicate BCNC stenosis. BCNC stenosis is generally associated with internal auditory canal stenosis and a joint assessment of these two indicators can more accurately predict the status of the cochlear nerve. However, magnetic resonance imaging should ultimately be performed to further verify the result achieved by computed tomography.
Chapter
Cochlear implantation (CI) is the primary intervention for patients with severe to profound sensorineural hearing loss. The mechanism of CI is to convert acoustic signals into electrical signals, directly stimulate the spiral ganglion (SGN), and transmit the signal to the auditory brainstem through the cochlear nerve (CN) fibers within the vestibulocochlear nerve (VCN). In patients with cochlear nerve deficiency (CND), the auditory brainstem can receive limited stimulation due to the reduced absolute number of CN fibers and the insufficient number of SGN. CND was once considered a contraindication to CI. In recent years, numerous studies have shown that patients with CND could benefit from CI. With advances in CI techniques, more patients with CND combined with inner ear malformation (IEM) are also included as indications for CI. This chapter describes CI outcomes in patients with CND with or without IEM and describes the role of radiological and electrophysiological factors in predicting hearing and speech outcomes after CI.
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MYH9 is a gene that encodes for a subunit of the myosin heavy chain IIA protein. Mutations in MYH9 are associated with hematologic abnormalities, renal dysfunction, and hearing loss. Bony cochlear nerve canal stenosis (CNCS), which is diagnosed on computed tomography (CT) imaging, has been associated with congenital deafness, cochlear nerve aplasia/hypoplasia, and inner ear malformations. We report two cases of CNCS presenting with profound congenital hearing loss whom we diagnosed with mutations in MYH9 and discuss the genotype-phenotype association and implications for management.
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Some patients with severe-profound sensorineural hearing loss (SNHL) with normal cochlear anatomical structure received cochlear implantation (CI) and the hearing and speech rehabilitation effect was not ideal. Through retrospective analysis, it was found that some of these patients had cochlear never canal (CNC) stenosis, or atresia in severe cases.This article reviews the development of the CNC, the diagnostic criteria of CNC stenosis and the results of hearing and speech rehabilitation in these patients after CI.
Article
Purpose Detection of cochlear nerve deficiency (CND) is usually straightforward using magnetic resonance imaging (MRI). In patients in whom MRI cannot be performed or imaging provides equivocal findings, computed tomography (CT) of the temporal bone might offer indirect evidence of CND. Our study aimed to derive a cut-off value for the diameter of the cochlear nerve canal (CNC) and internal auditory canal (IAC) in temporal bone CT to predict CND. Materials and Methods This retrospective study included 70 children with sensorineural hearing loss (32 with CND and 38 control patients). The height, width, and cross-sectional area of the IAC and diameter of the CNCs were determined using temporal bone CT. Receiver operating characteristic (ROC) and Student’s t-tests were performed for each parameter. Results The mean diameter of the CNCs was significantly smaller in children with CND than in the control group (1.2 mm versus 2.4 mm, p < .001). The optimal threshold for CNC for separation of the two groups was 1.9 mm, resulting in a sensitivity of 98.7 % and specificity of 89.2 %. The IAC dimensions could not distinguish between children with CND and controls. Conclusion A CNC diameter of less than 1.9 mm is a reliable predictor of CND in children with sensorineural hearing loss. Key Points: Citation Format
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For years, the term “Mondini dysplasia” was used to describe virtually every type of congenital inner ear malformation detected in imaging tests. More recently, histopathologic and imaging studies led to the description of several novel morphologic features, which were categorized into new groups according to morphologic patterns of the inner ear abnormalities. In addition, those new findings made possible to hypothesize potential pathophysiologic and embryogenic mechanisms involved in the genesis of each specific type of malformation. However, there are still obscure areas that still need to be better understood, such as quantitative and qualitative pathologic changes in the cellular, sensorial, and neural elements in the inner ear of patients with inner ear abnormalities. Therefore, histologic analysis of human temporal bones from patients who had inner ear malformations constitutes a tool of invaluable value. The clinical impact of past studies involving inner ear malformations is clear: today, cochlear implants or auditory brainstem implants are well indicated to treat hearing loss in patients with inner ear malformations, who were previously excluded from candidacy criteria. In the future, a broader understanding of yet obscure aspects of those malformations may increase even further the candidacy for those implants and create strategies for improved functional results. Thus, the objective of this chapter is to report, based on a review of the literature, otopathologic findings in human temporal bones from donors with inner ear malformations and to correlate the findings with embryogenic factors and their clinical implications.KeywordsHistopathologyEarInner earHumanCochleaVestibuleCochlear implant
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The course of FN through the temporal bone is thought to be dependent on the normal development of the related bony structures. Thus, abnormal formation of otic capsule may lead FN to follow a different route. In this chapter, the authors present a comprehensive classification of FN abnormalities in its all segments. Temporal bone computed tomography (CT) has a key role in detecting abnormal routes of FN as in inner ear malformations.The authors of this chapter classified FN abnormalities in 4 segments of the nerve as: Meatal segment: Type 1—Normal meatal segment (normal internal auditory canal, IAC): The midpoint diameter of IAC ≥ 2 mm.Type 2—Narrow meatal segment (narrow IAC): The midpoint diameter of the IAC < 2 mm.Type 3—Only facial canal: The IAC is absent and FN has its own canal.Type 4—Separate facial canal/duplicated IAC: IAC is present but FN has its own bony canal which is separated by the IAC.A narrow IAC (type 2) is generally seen in patients with cochlear hypoplasia. In more severe malformations such as Michel deformity, common cavity, and cochlear aplasia, only FC (type 3) is predominant type. Labyrinthine segment (LS): Type 1—Normal: LS makes a gentle curve between the geniculate ganglion and the IAC around the basal turn.Type 2—Displacement of the LS to the anterior part of the cochlea: This anterior displacement is evaluated into 3 groups according to the degree of anterior course.Type 2a—Mild anterior displacement: Cochlea is present and LS is located at the anterosuperior part of the cochlea instead of its normal posterolateral course. Cochlear hypoplasia type IV(CH-IV) has this type of LS.Type 2b—Moderate anterior displacement: LS occupies the usual location of the cochlea, and cochlea is absent or hypoplastic.Type 2c—Severe anterior displacement: LS is further anteriorly displaced beyond the usual location of the cochlea.Type 3—Superior displacement: In axial CT sections, LS is situated above the level of cochlea. IP-III causes superior displacement of the LS.Type 4—Straight LS: LS courses from IAC to geniculate ganglion in a non-curved, straight way so that FC looks like a continuation of IAC.A normally sized and developed cochlea is associated with a normal LS. Incomplete partition type I (IP-I) and IP-II are usually associated with a normal LS. As cochlea becomes hypoplastic or aplastic, LS displaces anteriorly in various degrees. Tympanic segment (TS): Type 1—Normal: TS is located superior and lateral to the oval window (OW) and stapes and inferior to lateral SCC.Type 2—Superiorly displaced: TS is located above the OW generally accompanying hypoplastic or aplastic lateral SCC.Type 3—At the OW: TS is located at the OW level at coronal CT sections.Type 4—Inferior to OW: TS is located below the OW, generally accompanying cochlear hypoplasia and abnormal SSCs.Type 5—Unclassified: Because of the aplasia of the OW, FN cannot be classified in relation to OW.In cases with cochlear hypoplasia, lateral semicircular canal is usually found to be aplastic or hypoplastic; this causes various degrees of dislocation of TS. Mastoid segment: Type 1—Normal facial recess (FR)/normal mastoid segment: if the space between the external auditory canal (EAC) and the FN is ≥2 mm.Type 2—Narrow FR: The distance between the EAC and the mastoid portion of the FN is <2 mm.Type 3—Unclassified: The mastoid portion of the FN cannot be visualized.The mean FR tends to be narrower in CH and in severe IEMs where cochlea is absent.KeywordsFacial nerveInner ear malformationsInternal auditory canalCochleaFacial recessOval windowSemicircular canalsCochlear implantation
Chapter
Preoperative imaging of the inner ear anomalies is central to proper treatment planning and patient management. For the imaging assessment of these patients high-resolution CT and MR imaging usually provide complementary information. The imaging of a CI or ABI candidate should not only help to fulfill the indication criteria but should also help to assess the integrity of the auditory pathway from the brainstem up to the temporal cortex.KeywordsInner ear anomaliesTemporal boneCochlear implantsComputed tomographyMagnetic resonance imaging
Chapter
Cochlear aperture (CA) (bony cochlear nerve canal) carries the cochlear nerve between the internal auditory canal (IAC) and modiolus. Atresia or stenosis of the CA has been found to correlate with cochlear nerve (CN) deficiency. CA can be considered as “normal” if the mid-portion or mid-modiolar width of the CA is ≥1.5 mm. CA is defined as “stenotic” when its mid-modiolar width is <1.5 mm. When the CA is not visible and it is occluded by bony tissue, CA is accepted as “atretic.” These abnormalities may be “isolated” or may present concomitantly with another IEMs. If these abnormalities do not accompany any other IEMs regarding the bony labyrinth they can be named as “isolated cochlear aperture atresia” and “isolated cochlear aperture stenosis.” In these situations, cochlear nerve is usually deficient.Since an atretic or stenotic CA is usually seen together with a narrow or absent internal auditory canal (IAC), the developmental relationship between IAC, CA, and CN will be discussed in this chapter. According to the most widely accepted hypothesis a deficient CN cannot release adequate amount of growth factors which result in interruption of development of bony structures. As the developing IAC requires the presence of a normal CN, it is likely that the CA also requires a similar neural stimulus for normal development.The recommended radiological evaluation method for the measurement of CA is high-resolution temporal bone computed tomography (HRCT) of the temporal bone. The measurement of CA should be performed at mid-modiolar section in axial sections. After identification of the fundus of the IAC, the length of the CA should be measured by drawing a perpendicular line from the base of the modiolus to the fundus of the IAC. Then, the mid-portion width of the CA can be measured. In this chapter, radiological evaluation is demonstrated by illustrations and CT images.Audiological findings in atretic or stenotic CA reveal CN deficiency. If there is no other cochlear malformation, otoacoustic emissions may be detected in the absence of auditory brainstem response (ABR). Thus, during neonatal screening these cases may be misdiagnosed as “auditory neuropathy.” A narrow or atretic cochlear aperture is generally associated with sensorineural hearing loss necessitating cochlear implantation (CI) or auditory brainstem implantation (ABI). Children with CN deficiency tend to have poor outcomes after CI. Therefore, decision making process between CI and auditory brainstem implantation (ABI) becomes more complicated and radiological findings must be supported by audiological data. Based on these facts, measurement of CA diameter may help predict cochlear nerve status and CI outcomes.KeywordsBony cochlear nerve canalCochlear apertureInternal auditory canalCochlear nerve deficiencyUnilateral sensorineural hearing loss
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Hearing loss in pediatric age group is associated with many congenital temporal bone disorders. Aberrant development of various ear structures leads into either conductive or sensorineural hearing loss. Knowledge of the embryology and anatomical details of various compartments of the ear help better understanding of such disorders. In general, abnormalities of external and middle ears result in conductive hearing loss. Whereas abnormalities of inner ear structures lead into sensorineural hearing loss. These abnormalities could occur as isolated or part of syndromes. Temporal bone disorders are a significant cause of morbidity and developmental delays in children. Imaging evaluation of children presented with hearing loss is paramount in early diagnosis and proper management planning. Our aim is to briefly discuss embryology and anatomy of the pediatric petrous temporal bones. The characteristic imaging features of commonly encountered congenital temporal bone disorders and their associated syndromes will be discussed.
Article
Objective This study aimed to evaluate the association between cochlear nerve canal dimensions and semicircular canal abnormalities and to determine the distribution of bony labyrinth anomalies in patients with cochlear nerve canal stenosis. Method This was a retrospective study in which high-resolution computed tomography images of paediatric patients with severe-to-profound sensorineural hearing loss were reviewed. A cochlear nerve canal diameter of 1.5 mm or less in the axial plane was classified as stenotic. Semicircular canals and other bony labyrinth morphology and abnormality were evaluated. Results Cochlear nerve canal stenosis was detected in 65 out of 265 ears (24 per cent). Of the 65 ears, 17 ears had abnormal semicircular canals (26 per cent). Significant correlation was demonstrated between cochlear nerve canal stenosis and semicircular canal abnormalities ( p < 0.01). Incomplete partition type II was the most common accompanying abnormality of cochlear nerve canal stenosis (15 out of 65, 23 per cent). Conclusion Cochlear nerve canal stenosis is statistically associated with semicircular canal abnormalities. Whenever a cochlear nerve canal stenosis is present in a patient with sensorineural hearing loss, the semicircular canal should be scrutinised for presence of abnormalities.
Article
Objectives: To investigate novel variants in hearing loss genes and clinical factors affecting audiometric outcomes of cochlear implant (CI) patients. Background: Approximately 50% of hearing loss has a genetic etiology, with certain genetic variants more prevalent in specific ethnic groups. Different variants and some clinical variables including inner ear malformations result in different prognoses or clinical outcomes after CI. Methods: Medical and genetic testing records of pediatric CI patients were reviewed for clinical variables. Minor allele frequencies of variants were obtained from Genome Aggregation Database (gnomAD) and variants were classified for pathogenicity. Standard statistical testing was done using Fisher's exact, Wilcoxon, and Spearman correlation tests. Results: Eighteen CI patients with genetic test results had pathogenic variants, including six patients with syndromic hearing loss and six patients with known GJB2 variants. Novel pathogenic variants were noted in CHD7, ADGRV1, and ARID1B, with variants in the latter two genes identified in Hispanic patients. Overall, carriage of genetic variants was associated with better pre-CI audiometric thresholds at 2000 Hz (p = 0.048). On the other hand, post-CI thresholds were significantly worse in patients with inner ear malformations, particularly in patients with atretic cochlear nerve canals. Conclusion: Four novel pathogenic variants were identified, which contributes to knowledge of allelic spectrum for hearing loss especially in Hispanic patients. In this cohort, carriage of pathogenic variants particularly of GJB2 variants was associated with better pre-CI audiometric thresholds, while patients with inner ear malformations had worse post-CI audiometric thresholds.
Article
The mean width of the bony cochlear nerve canal (BCNC) was 2.02±0.56 mm on the implanted side and 2.04±0.49 mm on the contralateral side, which was significantly different from the control (2.36±0.28 mm). The mean cross‐section value (CSV) of cochlear nerve (CN) was 0.6684±0.3202 on the implanted side and 0.6813±0.3319 on the contralateral side. In contrast to the BCNC width, the CSV of the CN was negatively correlated with behavioral threshold (T level) and maximum comfort (C level). BCNC width and T level showed weak associations with the Categories of Auditory Performance score at 1 year postoperatively. Anatomical factors (BCNC width and CSV of CN) and T and C levels may play a significant role as some predictors of cochlear implant performance. This article is protected by copyright. All rights reserved.
Chapter
Temporal bone imaging has a well-deserved reputation as being one of the more challenging aspects of radiology. To paraphrase a neurotology colleague, an amazing amount of intricate anatomy is packed into a very small box. Furthermore, the pathology affecting these structures can be very subtle and affect minute areas. Understanding the myriad appearances of normal structures in unusual places or of unexpected size is quite important. Frequently, these variations are of no consequence but occasionally a similar structure of a comparable size and location that is asymptomatic in one person may be problematic in another.
Article
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In 1996, a new type of bilateral hearing disorder was discerned and published almost simultaneously by Kaga et al. [1] and Starr et al. [2]. Although the pathophysiology of this disorder as reported by each author was essentially identical, Kaga used the term "auditory nerve disease" and Starr used the term "auditory neuropathy". Auditory neuropathy (AN) in adults is an acquired disorder characterized by mild-to-moderate pure-tone hearing loss, poor speech discrimination, and absence of the auditory brainstem response (ABR) all in the presence of normal cochlear outer hair cell function as indicated by normal distortion product otoacoustic emissions (DPOAEs) and evoked summating potentials (SPs) by electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology including mutations of the OTOF and/or OPA1 genes. Most of the subsequent reports in the literature discuss the various auditory profiles of patients with AN [3,4] and in this report we present the profiles of an additional 17 cases of adult AN. Cochlear implants are useful for the reacquisition of hearing in adult AN although hearing aids are ineffective. In 2008, the new term of Auditory Neuropathy Spectrum Disorders (ANSD) was proposed by the Colorado Children's Hospital group following a comprehensive study of newborn hearing test results. When ABRs were absent and DPOAEs were present in particular cases during newborn screening they were classified as ANSD. In 2013, our group in the Tokyo Medical Center classified ANSD into three types by following changes in ABRs and DPOAEs over time with development. In Type I, there is normalization of hearing over time, Type II shows a change into profound hearing loss and Type III is true auditory neuropathy (AN). We emphasize that, in adults, ANSD is not the same as AN. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Article
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Approximately 20% of patients with congenital sensorineural hearing loss have radiographic abnormalities of the inner ear. A broad spectrum of anomalous patterns have been described, most of which have been lumped together under the term “Mondini's dysplasia.” We feel that this grouping of many dissimilar entities under a single umbrella term is unwarranted. Based on a review of 63 patients with 98 congenitally malformed ears, we have been able to recognize a number of distinct anatomic patterns from their radiographic appearance. A remarkable similarity between these morphologies and the appearance of the inner ear at various stages of embryogenesis was found. This led us to propose a classification system based upon the theory that these deformities result from an arrest of development during varying stages of inner ear organogenesis.
Article
This is the first in a series of clinics on ENT imaging. The purpose of this series is to review important technical, anatomic and pathologic features of interest to the ENT clinician and surgeon.
Article
Auditory brainstem implants (ABIs) can provide useful auditory perception and language development in deaf children who are not able to use a cochlear implant (CI). We prospectively followed up a consecutive group of 64 deaf children up to 12 years following ABI surgery. The etiology of deafness in these children was: cochlear nerve aplasia in 49, auditory neuropathy in 1, cochlear malformations in 8, bilateral cochlear postmeningitic ossification in 3, neurofibromatosis type 2 in 2, and bilateral cochlear fractures due to a head injury in 1. Thirty-five children had other congenital nonauditory disabilities. Twenty-two children had previous CIs with no benefit. Fifty-eight children were fitted with the Cochlear 24 ABI device and 6 with the MedEl ABI device, and all children followed the same rehabilitation program. Auditory perceptual abilities were evaluated on the Categories of Auditory Performance (CAP) scale. No child was lost to follow-up, and there were no exclusions from the study. All children showed significant improvement in auditory perception with implant experience. Seven children (11%) were able to achieve the highest score on the CAP test; they were able to converse on the telephone within 3 years of implantation. Twenty children (31.3%) achieved open set speech recognition (CAP score of 5 or greater) and 30 (46.9%) achieved a CAP level of 4 or greater. Of the 29 children without nonauditory disabilities, 18 (62%) achieved a CAP score of 5 or greater with the ABI. All children showed continued improvements in auditory skills over time. The long-term results of ABI surgery reveal significant auditory benefit in most children, and open set auditory recognition in many. © 2014 S. Karger AG, Basel.
Article
Cochlear implantation is a proven treatment for bilateral severe to profound hearing loss. Imaging has an important role in deciding candidacy, providing realistic preoperative counselling, and predicting postoperative outcomes. Imaging also provides information about the potential difficulties a surgeon may encounter during the implantation. High-resolution computed tomography and high-resolution magnetic resonance imaging complement each other in assessing different aspects of the temporal bone and the auditory pathway in such patients. This review provides a structured format for reading pre-cochlear implant imaging studies with special focus on the surgeon's expectations in order to prepare a clinically relevant report. A constant communication between the imaging specialist and the cochlear implant surgeon improves image interpretation and ensures a successful implantation.
Article
Objective: The aim of this study was to characterize the various bony anomalies of the inner ear in patients with unilateral sensorineural hearing loss using high-resolution temporal bone computed tomography and establish the relationship between hearing and the diameter of the bony cochlear nerve canal. Methods: We performed a retrospective review of 51 patients (mean age 11 years, range 0-20 years, 27 boys, 24 girls) who were diagnosed with unilateral sensorineural hearing loss with an audiogram. Coronal and axial diameter of the inner ear structures, including the internal auditory canal, bony cochlear nerve canal, and each turn of the cochlea and semicircular canals, were measured with high-resolution temporal bone computed tomography. The mean values (± 2 standard deviations) were calculated and compared between sensorineural hearing loss and normal ears, and between narrow bony cochlear nerve canal and normal bony cochlear nerve canal ears. Bony cochlear nerve canal atresia/stenosis was defined as a value less than 1.4mm in axial images. Results: The diameter of the bony cochlear nerve canal was significantly smaller in sensorineural hearing loss ears than in normal ears (p<.05). Associated inner ear anomalies, such as IAC stenosis (24%), cochlear hypoplasia (7-17%), and narrow semicircular canal bony island (8%) were only observed in the narrow bony cochlear nerve canal group. This group also showed statistically significant, severe to profound hearing loss compared to the normal bony cochlear nerve canal group (p<.05, R(2)=12.8%). Conclusions: Most (57%) of the unilateral sensorineural hearing loss ears had bony cochlear nerve canal stenosis/atresia and this group showed associated inner ear anomalies. When the diameter of the bony cochlear nerve canal was less than 1.4mm, pure tone audio averages were more than 70 dB HL in most ears.
Article
Objective: Radiological and genetic examination has recently advanced for diagnosis of congenital hearing loss. The aim of this study was to elucidate the prevalence of inner-ear and/or internal auditory canal malformations in children with unilateral sensorineural hearing loss (USNHL) for better management of hearing loss and genetic and lifestyle counseling. Methods: We conducted a retrospective study of charts and temporal bone computed tomography (CT) findings of 69 consecutive patients 0-15 years old with USNHL. In two cases, genetic examination was conducted. Results: Of these patients, 66.7% had inner-ear and/or internal auditory canal malformations. The prevalence of malformations in infants (age <1 year) was 84.6%, which was significantly higher than that in children 1-15 years old (55.8%; p<0.01). Almost half of the patients (32; 46.4%) had cochlear nerve canal stenosis; 13 of them had cochlear nerve canal stenosis alone, and in 19 it accompanied other malformations. Internal auditory canal malformations were observed in 22 subjects (31.8%), 14 (20.3%) had cochlear malformations, and 5 (7.2%) had vestibular/semicircular canal malformations. These anomalies were seen only in the affected ear, except in two of five patients with vestibular and/or semicircular canal malformations. Two patients (2.9%) had bilateral enlarged vestibular aqueducts. Mutations were found in SLC26A4 in one of the two patients with bilateral large vestibular aqueducts. The prevalence of a narrow internal auditory canal was significantly higher in subjects with cochlear nerve canal stenosis (50.0%) than in subjects with normal cochlear nerve canals (11.1%; p<0.01). There were no correlations between the type and number of malformations and hearing level. Conclusions: The prevalence of inner-ear and/or internal auditory canal malformations detected by high-resolution temporal bone CT in children with USNHL was very high. Radiological and genetic examination provided important information to consider the pathogenesis and management of hearing loss. Temporal bone CT should be recommended to children with USNHL early in life. SLC26A4 mutation also should be examined in cases with bilateral enlarged vestibular aqueduct.
Article
Objectives/hypothesis: To evaluate outcomes after cochlear implantation in children with anomalous cochleovestibular anatomy, a review of radiological classification, surgical implantation, and outcome of 103 children with such anomalies was performed. The hypothesis was that children with anomalous cochleovestibular anatomy would have poorer outcomes and therefore be poorer candidates as a result of their diminished ability to interpolate and use auditory information delivered through a cochlear implant. Study design: A series of studies was carried out to review the cochleovestibular anomalies among 298 children implanted over the decade ending in January 2002. Children were grouped based on cochleovestibular anatomy as follows: normal (n = 195), common cavity deformity (n = 8), hypoplastic cochlea (n = 16), incomplete partition (n = 42), and vestibular aqueduct enlargement (n = 37). Concomitant anomalies of the posterior labyrinth (n = 26) and internal auditory canal/cochlear canal (n = 11) were also identified. Findings at surgery, postoperative speech perception outcomes, and speech processor programmability were examined as a function of cochleovestibular anatomy. Methods: A database containing demographics (age at implant, duration of implant use), audiological characteristics, pure-tone average, surgical findings (cerebrospinal fluid leak/perilymph leak, abnormal facial nerve anatomy), speech perception data (from two closed-set and three open-set tests), and data relating to speech processor programmability were used for analysis. Electrically evoked auditory brainstem response was measured in 94 of the children (2 cases of common cavity deformity, 7 of hypoplastic cochlea; 10 of incomplete partition; and 12 of vestibular aqueduct enlargement). Response morphological findings were assessed by visual inspection of the waveforms. Data were analyzed using analyses of variance with post hoc testing using the Bonferroni multiple-comparisons test. To further assess differences in outcomes between different categories of cochleovestibular anomalies, linear regression analyses were performed. The significance level was set at P < .05. Results: The use of high-resolution imaging techniques resulted in the detection of a cochleovestibular anomaly in 35% of implanted ears. Implantation was more challenging in 24% of the children as a result of abnormal middle ear anatomy (17.5%) or cerebrospinal fluid leak/perilymph leak (6.7%). There was no significant difference in speech perception scores in children with anomalous cochleae compared with children with normal cochleovestibular anatomy. Children with narrowing of the internal auditory canal/cochlear canal performed more poorly than all other groups. Children with common cavity deformity and hypoplastic cochlea had reduced dynamic range and increased incidence of facial simulation and were judged to be more difficult to program despite the fact that no fewer electrodes were inserted. Children with common cavity deformity and hypoplastic cochlea tended to require wider pulse widths more often than children in other groups, and these requirements were associated with abnormal morphological findings on evoked auditory brainstem response testing. Conclusion: The authors have been continuing to assess the candidacy of each child applying for cochlear implantation individually, and the results of present study have suggested that the presence of anomalous cochleovestibular anatomy, with the exception of narrowing of the internal auditory canal/cochlear canal, should not play a significant role in candidacy assessment. Children with narrow internal auditory canal/cochlear canal should be carefully and individually considered. In children with anomalous cochleovestibular anatomy, the potentially increased difficulty in the establishment of optimal stimulation levels and the higher potential for surgical difficulty must be weighed in candidacy decisions but do not universally preclude successful implantation and a good outcome.
Article
Establish normative histopathologic data on the dimensions of the cochlear nerve canal (CNC). Evidence suggests that when the CNC is stenotic, the cochlear nerve may be hypoplastic. There is clear agreement in the literature that an internal auditory canal less than 2 mm in diameter is a relative contraindication to cochlear implantation in children. However, there has only been recent recognition in research that a narrowed CNC may lead to diminished ability to interpolate and use auditory information delivered through a cochlear implant. However, there is no consensus in the literature on the normal diameter of the CNC and what parameters should be used to determine stenosis. In addition, no normative histopathologic data is available for CNCs. This study evaluated histopathologic axial sections from normal human temporal bones to measure the cochlear nerve canal in 110 individuals, aged 0-100 years. The maximum CNC diameter in each normal patient was identified and measured. The mean CNC diameter was 2.26 mm with a standard deviation of 0.25 mm. There were no differences in the CNC diameters between males and females or with increasing age. These measurements should provide a normative reference for comparison in histopathologic and radiographic assessment of any patient with suspected cochlear nerve canal stenosis.
Article
Cochlear implantation has become an accepted treatment for deafness. As the frequency of cochlear implantation has increased, requests for images have also increased in the work-up for candidates. An absent cochlear nerve (CN) is a contraindication to cochlear implantation. Therefore, MRI is performed to evaluate the CN in patients with sensorineural hearing loss. Recently, some authors have reported the relationship between cochlear nerve canal (CNC) stenosis and CN hypoplasia. To review the relationship between CNC and CN. During a period of 78 months, 21 children (42 ears) with unilateral or bilateral sensorineural hearing loss underwent both HRCT and MRI of the cochlear nerve. We retrospectively reviewed two factors: the evaluation of inner ear malformations and the relationship between CNC stenosis and CN hypoplasia. Inner ear malformations were recognized in ten ears. The mean CNC diameter was approximately 2 mm (ranging from 0.6 to 2.7 mm). CN hypoplasia was seen in eight of the 42 ears; all eight were associated with CNC stenosis (<or=1.5 mm). Of the 34 ears with normal CN, 32 had CNC >1.5 mm in diameter and the remaining two ears, with incomplete partition type I, had CNC stenosis. Children with CNC stenosis had a high incidence of CN hypoplasia. CNC stenosis (<or=1.5 mm) suggests CN hypoplasia. On the other hand, CN hypoplasia was not seen in children with CNC diameter >1.5 mm. Therefore, we conclude that children with CNC stenosis or malformations on HRCT should receive MR imaging of the CN.
Article
The aim of our study is to present the results of 11 children where auditory brainstem implantation (ABI) was successfully performed to restore hearing. Case presentation. This study was conducted at the departments of Otolaryngology and Neurosurgery at Hacettepe University Ankara, Turkey. Between July 2006 and April 2008, 11 prelingual (30-56 mo) deaf children with several cochlear malformations had ABI. All patients were programmed and were enrolled in auditory verbal therapy sessions and family counseling programs at Hacettepe Auditory Verbal Center. The evaluation was performed at preimplant and again 1, 3, 6, 9, and 12 months post-switch on. The main test components composing this test battery were Ling 6 Sound Detection-Identification Test, Word Identification Test in Turkish, Meaningful Auditory Integration Scale, and Meaningful Use of Speech Scale. Successful brainstem implantations were performed in all patients with retrosigmoid approach. Six children gained basic audiologic functions and were able to recognize and discriminate sounds, and many could identify environmental sounds such as a doorbell and telephone ring by the third month of ABI. Improvement in mean performance on Meaningful Auditory Integration Scale is apparent for all ABI children. Improvement in Meaningful Use of Speech Scale scores in 2 patients, demonstrating that the child using its own voice for speech performance, was observed between the baseline and 12th month. First, 5 children were able to identify Ling's 6 sound by the end of 2 to 6 months, and 2 of them also started to identify words due to their pattern differences and multisyllabic word identification by 6 to 9 months. Two children with Attention Deficit Hyperactivity Disorder have made slower progress than the other children with ABIs. Our preliminary results show that there is adequate contribution of brainstem implants in the development of auditory-verbal skills. Additional handicaps slow the progress of the prelingually deaf children.
Article
Inner ear malformations constitute about 20% of congenital sensorineural hearing loss. In this review article an updated classification of cochlear malformations is provided. Incomplete partition and cochlear hypoplasia cases are each divided further into three groups. There are two main difficulties in the surgery of inner ear malformations; gusher and facial nerve abnormalities. Radiological features of malformations necessary to identify these problems preoperatively are discussed. Facial nerve abnormalities that may occur are described. Two different types of cerebrospinal fluid leakage are defined and necessary measures to prevent leakage are described. Standard and modified surgical approaches to overcome the described problems are described with literature findings. Finally meningitis which may occur with and without cochlear implantation in this special group of patients is emphasized. This is common in incomplete partition type I patients and is usually due to a fistula in one of the windows (usually oval window) which occurs as a result of cerebrospinal fluid pressure. This is a medical emergency leading to potential meningitis and measures that should be taken to stop the leak as soon as possible are described.
Article
Approximately 20% of patients with congenital sensorineural hearing loss have radiographic abnormalities of the inner ear. A broad spectrum of anomalous patterns have been described, most of which have been lumped together under the term "Mondini's dysplasia." We feel that this grouping of many dissimilar entities under a single umbrella term is unwarranted. Based on a review of 63 patients with 98 congenitally malformed ears, we have been able to recognize a number of distinct anatomic patterns from their radiographic appearance. A remarkable similarity between these morphologies and the appearance of the inner ear at various stages of embryogenesis was found. This led us to propose a classification system based upon the theory that these deformities result from an arrest of development during varying stages of inner ear organogenesis.
Article
Surgery of the internal auditory canal has today become a new horizon for the otologist. The knowledge of its anatomy and normal variation is therefore essential. The most important aspect is the variation in dimensions. The present study compares the dimensions of the canals on the two sides in the same individual. One method of study is by preparing casts of the internal auditory canals in cadaveric temporal bones. The other is a radiographic study by using tomograms in the frontal projection. The study reveals that although the diameters of the canals vary a great deal from person to person, the diameters of the canals of the two sides are usually fairly well-matched, especially in the vertical diameter.
Article
To evaluate the length and width of the bony canal of the cochlear nerve in patients with congenital sensorineural hearing loss (SNHL) who have "normal" findings at thin-section computed tomography (CT) of the temporal bone. The authors retrospectively evaluated the length and width of the bony canal for the cochlear nerve in two groups of patients. The first group was composed of 33 patients with profound SNHL and no demonstrable abnormality at thin-section CT. The control group was composed of 50 patients who underwent temporal bone CT for causes unrelated to SNHL. The mean value +/- SD was calculated for both cohorts. Statistical analysis consisted of the nonparametric Wilcoxon rank sum test with the NPAR1WAY program. The length and width of the bony canal for the cochlear nerve were significantly smaller in patients with SNHL than in the control group (P <.05) The hypoplastic bony canal for the cochlear nerve in patients with SNHL may be indicative of a previously unrecognized embryologic malformation of the cochlear nerve.
Article
Magnetic resonance imaging (MRI) is presently the study of choice for assessment of the internal auditory canal (IAC). MRI provides excellent assessment of the IAC and the bony changes occurring in the canal walls, and it provides excellent demonstration of the content of the canal. Pathological processes arising within the IAC are well visualized by various MR sequences. The possibility of demonstrating masses as small as 2 mm has propelled MRI into the leading role for diagnosis of vestibular schwannoma. Unfortunately, the high cost of MR has been a limiting factor in its use as a screening test for patients with sensorineural hearing loss (SNHL) of unknown origin. Auditory brain stem response has been widely used as a screening procedure, but this test fails to recognize small lesions and cannot be used whenever hearing loss is severe. In this article, we will discuss our approach to assessment of the IAC in patients with retrocochlear SNHL or vestibular symptoms of central origin, review the pathological processes involving the IAC walls or arising within the canal, emphasizing the appropriate MRI sequences used for diagnosis.
Article
Hair cell (HC) and supporting cell (SC) productions are completed during early embryonic development of the mammalian cochlea. This study shows that acutely dissociated cells from the newborn rat organ of Corti, developed into so-called otospheres consisting of 98% nestin (+) cells when plated on a non-adherent substratum in the presence of either epidermal growth factor (EGF) or fibroblast growth factor (FGF2). Within cultured otospheres, nestin (+) cells were shown to express EGF receptor (EGFR) and FGFR2 and rapidly give rise to newly formed myosin VIIA (+) HCs and p27(KIP1) (+) SCs. Myosin VIIA (+) HCs had incorporated bromodeoxyuridine (BrdU) demonstrating that they were generated by a mitotic process. Ultrastructural studies confirmed that HCs had differentiated within the otosphere, as defined by the presence of both cuticular plates and stereocilia. This work raises the hypothesis that nestin (+) cells might be a source of newly generated HCs and SCs in the injured postnatal organ of Corti.
Article
The purpose of this study was to determine the normal variations of cochlear nerve canal dimensions, which is useful information to have when assessing congenital malformations, i.e. during the preoperative evaluation of cochlear implant candidates. The length and diameter of the cochlear nerve canal were measured in 117 casts from randomly selected temporal bone specimens obtained from the Uppsala Temporal Bone Laboratory. In 16 of the casts the dimensions were correlated with those obtained from CT scans of the same temporal bone. Measurements were also made from CT examinations of the temporal bone of 50 patients referred for evaluation of cholesteatoma or chronic otitis media. The mean length and diameter in the axiopetrosal plane measured in casts were 1.17 and 2.58 mm, respectively. The mean diameter in the axial plane was 2.59 mm. The mean length and diameter determined from CT scans of the specimens were 1.19 and 1.98 mm, respectively. The mean length and diameter determined from CT examinations of patients were 1.08 and 1.91 mm, respectively. In conclusion, the cochlear nerve canal is short, with a circular cross-section. If the diameter of the canal is < 1.4 mm then the possibility of cochlear nerve abnormality should be considered; if it is > 3.0 mm then other anomalies may coexist.
Article
To describe a group of children exhibiting electrophysiologic responses characteristic of auditory neuropathy (AN) who were subsequently identified as having absent or small cochlear nerves (i.e., cochlear nerve deficiency). A retrospective review of the clinical records, audiological testing results, and magnetic resonance imaging (MRI) studies. Fifty-one of 65 children with AN characteristics on auditory brain stem response (ABR) testing had MRI available for review. Nine (18%) of these 51 children with ABR characteristic of AN have been identified as having small (N = 2; 4%) or absent (N = 7; 14%) cochlear nerves on MRI. Of the nine children with cochlear nerve deficiency, five (56%) were affected unilaterally and four (44%) bilaterally. Eight of nine presented after failing a newborn infant hearing screening, whereas one presented at 3 yr of age. On diagnostic ABR testing, all 9 children (9 of 13 affected ears; 69%) had evidence of a cochlear microphonic (CM) and absent neural responses in at least one ear. In the unilateral cases, AN characteristics were detected in all affected ears. In bilateral cases, at least one of the ears in each child demonstrated the AN phenotype, whereas the contralateral ear had no CM identified. Only one ear with cochlear nerve deficiency had present otoacoustic emissions as measured by distortion-product otoacoustic emissions. In children with appropriate available behavioral testing results, all ears without cochlear nerves were identified as having a profound hearing loss. Only 4 (31%) of the 13 ears with cochlear nerve deficiency had a small internal auditory canal on MRI. Children with cochlear nerve deficiency can present with electrophysiologic evidence of AN. These children frequently refer on newborn screening examinations that use ABR-based testing methods. Similar to other causes of AN, diagnostic ABR testing will show a CM with absent neural responses. Given that 9 (18%) of 51 children with available MRI and electrophysiologic characteristics of AN in our program have been identified as having cochlear nerve deficiency makes this a relatively common diagnosis. These findings suggest that MRI is indicated for all children diagnosed with AN. Moreover, electrophysiologic evidence of unilateral AN in association with a profound hearing loss should make the clinician highly suspicious for this problem. Although children with cochlear nerve deficiency who have a small nerve may benefit from cochlear implantation or amplification, these interventions are obviously contraindicated in children with completely absent cochlear nerves.
Article
To describe the internal auditory canal (IAC) and inner ear morphologic characteristics of children with cochlear nerve (CN) deficiency. Retrospective case series. Tertiary referral center. Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution magnetic resonance imaging (MRI). MRI of the brain. Clinical evaluation. Review of medical records, audiological testing results, and imaging studies. Images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs and inner ears. Audiometric thresholds were evaluated in all subjects. Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution MRI. A review of the medical records, audiologic testing results, and imaging studies was undertaken. The images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs, and inner ears. The audiometric thresholds were evaluated in all subjects. Among the 14 patients, 5 had known syndromes. MRI allowed an exact specification of the nervous structures within all ears with normal-size IACs. Precise characterization of the nerves in ears with small IACs was more difficult, requiring a consideration of both imaging findings and functional parameters. Five children had bilateral deficient CNs, whereas the remaining 9 subjects were affected unilaterally. Thus, 19 ears had CN deficiency (absent CN, 16; small CN, 3). Eleven ears had normal-size IACs and deficient CNs. Of the 9 ears with small IACs, 8 had deficient CNs (absent, 7; small, 1) on the basis of both MRI and functional assessments. Two ears with small IACs had clear morphologic and/or functional evidence for the presence of a CN: one had a small-size CN on MRI, whereas another had a single nerve in a small IAC with present facial and auditory functions. The findings of this study suggest that CN deficiency is not an uncommon cause of congenital hearing loss. The findings that most ears with CN deficiency had normal IAC morphology and that two ears with small IACs had CNs present indicate that IAC morphology is an unreliable surrogate marker of CN integrity. On the basis of these findings, we think that high-resolution MRI, rather than CT imaging, should be performed in all cases of pediatric hearing loss, especially in those cases where profound hearing loss has been documented. For ears with small IACs, the resolution of MRI currently remains limiting. In these cases, the determination of CN status frequently requires a variety of anatomic (CT and MRI) and functional tests (auditory brainstem response, otoacoustic emissions, behavioral audiometry, and physical examination).
Article
Sensorineural hearing loss (SNHL) due to internal auditory canal (IAC) stenosis with hypoplasia of the cochleovestibular nerve is a rare disorder. The diagnosis of the IAC stenosis requires both high resolution computed tomography scan (HRCT) and magnetic resonance imaging (MRI). A retrospective review over 6 years in an academic tertiary referral center was performed. Six patients with congenital SNHL were diagnosed with congenital IAC stenosis. Four had unilateral and two had bilateral IAC stenosis after imaging. MRI showed hypoplastic vestibulocochlear nerve in all cases. This paper highlights the importance of imaging in diagnosing IAC stenosis and detecting the presence of cochleovestibular nerve in cases of congenital SNHL.
Article
This preliminary study demonstrates the development of hearing ability and shows that there is a significant improvement in some cognitive parameters related to selective visual/spatial attention and to fluid or multisensory reasoning, in children fitted with auditory brainstem implantation (ABI). The improvement in cognitive paramenters is due to several factors, among which there is certainly, as demonstrated in the literature on a cochlear implants (CIs), the activation of the auditory sensory canal, which was previously absent. The findings of the present study indicate that children with cochlear or cochlear nerve abnormalities with associated cognitive deficits should not be excluded from ABI implantation. The indications for ABI have been extended over the last 10 years to adults with non-tumoral (NT) cochlear or cochlear nerve abnormalities that cannot benefit from CI. We demonstrated that the ABI with surface electrodes may provide sufficient stimulation of the central auditory system in adults for open set speech recognition. These favourable results motivated us to extend ABI indications to children with profound hearing loss who were not candidates for a CI. This study investigated the performances of young deaf children undergoing ABI, in terms of their auditory perceptual development and their non-verbal cognitive abilities. In our department from 2000 to 2006, 24 children aged 14 months to 16 years received an ABI for different tumour and non-tumour diseases. Two children had NF2 tumours. Eighteen children had bilateral cochlear nerve aplasia. In this group, nine children had associated cochlear malformations, two had unilateral facial nerve agenesia and two had combined microtia, aural atresia and middle ear malformations. Four of these children had previously been fitted elsewhere with a CI with no auditory results. One child had bilateral incomplete cochlear partition (type II); one child, who had previously been fitted unsuccessfully elsewhere with a CI, had auditory neuropathy; one child showed total cochlear ossification bilaterally due to meningitis; and one child had profound hearing loss with cochlear fractures after a head injury. Twelve of these children had multiple associated psychomotor handicaps. The retrosigmoid approach was used in all children. Intraoperative electrical auditory brainstem responses (EABRs) and postoperative EABRs and electrical middle latency responses (EMLRs) were performed. Perceptual auditory abilities were evaluated with the Evaluation of Auditory Responses to Speech (EARS) battery - the Listening Progress Profile (LIP), the Meaningful Auditory Integration Scale (MAIS), the Meaningful Use of Speech Scale (MUSS) - and the Category of Auditory Performance (CAP). Cognitive evaluation was performed on seven children using the Leiter International Performance Scale - Revised (LIPS-R) test with the following subtests: Figure ground, Form completion, Sequential order and Repeated pattern. No postoperative complications were observed. All children consistently used their devices for >75% of waking hours and had environmental sound awareness and utterance of words and simple sentences. Their CAP scores ranged from 1 to 7 (average =4); with MAIS they scored 2-97.5% (average =38%); MUSS scores ranged from 5 to 100% (average =49%) and LIP scores from 5 to 100% (average =45%). Owing to associated disabilities, 12 children were given other therapies (e.g. physical therapy and counselling) in addition to speech and aural rehabilitation therapy. Scores for two of the four subtests of LIPS-R in this study increased significantly during the first year of auditory brainstem implant use in all seven children selected for cognitive evaluation.