-
[show abstract]
[hide abstract]
ABSTRACT: Although much is known about the cerebral neural plasticity that occurs after deafness, it is unclear how much time is required for its development or what other cortical changes may consequently occur. This study provides a longitudinal assessment of cerebral cortical neural plasticity, as manifested in adult deafened cats. A total of 5 male cats were subjected to whole cortex analysis of glucose metabolic activity via 2-deoxy-2[(18)F] fluoro-D-glucose (FDG) micro-positron emission tomography (PET). The imaging was performed at the baseline state of normal hearing and then at 4, 9, 24, and 33 months after the induction of deafness. We compared glucose metabolism between the normal hearing state and each deafened state by using voxel-based statistical analysis (P<0.005). Significant changes were observed in the primary auditory (A1) and primary visual (V1) cortices. A bilateral metabolic decrease was observed in A1 areas and in temporal auditory fields, the extent of which was significantly increased at Month 9. Then it was declined at Month 24. And finally it was disappeared by Month 33. Auditory cortical plasticity subsequent to deafness was thus demonstrated. Furthermore, a significant metabolic upsurge occurred in bilateral occipital areas at Month 33. This increase, involving bilateral occipital and thalamic areas of V1, suggests compensatory hyperactivity of the visual cortex after deafness.
Brain research 10/2010; 1354:85-90. · 2.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Speechreading is a visual communicative skill for perceiving speech. In this study, we tested the effects of speech experience and deafness on the speechreading neural network in normal hearing controls and in two groups of deaf patients who became deaf either before (prelingual deafness) or after (postlingual deafness) auditory language acquisition. Magnetic signals from the cerebral cortex were recorded using a 306-channel magnetoencephalographic system. During magnetoencephalographic measurements, subjects were asked to perform a speechreading task from video clips of a female speaker either pronouncing syllables (speechreading condition) or showing closed-mouth movement. The sources of the evoked fields were modelled using equivalent current dipoles, the origins of which were fitted to the intracranial space based on magnetic resonance imaging findings. During the speechreading condition, the latency of auditory cortex activation was shorter in the postlingual deafness group than in the normal hearing control group. This parameter negatively correlated with speechreading scores measured clinically. Furthermore, as the duration of deafness increased, the latency of auditory cortex activation decreased exponentially. However, no such correlation was found in the prelingual deafness group which differed significantly from the two other groups in this respect. The latency of auditory cortex activation was significantly longer in the prelingual deafness group than in the two other groups. Thus, auditory experience may be crucial for the development of a normal neural network for speechreading. The pre-existing speechreading network in the postlingual deafness group is made more efficient by speeding up the neural response.
Brain 07/2009; 132(Pt 10):2761-71. · 9.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: It is commonly held that losing one sense provokes cross-modal takeover of deprived cortical areas, and therefore results in a benefit for the remaining modalities. Using functional magnetic resonance imaging (fMRI), we assessed the impact of acquired deafness on the brain network related to speechreading and teased apart cortical areas with responses showing long-term reorganization, i.e. time-dependent plasticity over 4-48 months of deafness, from those expressing compensation, i.e. performance-related activity. Nine deaf patients (7 women, age; mean +/- SE. = 50.2 +/- 4.8) and control subjects performed equally well in a visual speechreading task but deaf patients activated the left posterior superior temporal cortex more than controls. This effect correlated with speechreading fluency but not with the duration of sensory deprivation, thus arguing against long-term reorganization as the source of these cross-modal effects. To the contrary, cross-modal activation in the left posterior superior temporal cortex of deaf patients decreased with deafness duration. Our observation that cross-modal effects were most pronounced right after deafness onset is at odds with the classical view on brain reorganization. We suggest that functional compensation of sensory deprivation does not require slowly progressive colonization of superior temporal regions by visual inputs, but can exploit a switch to pre-existing latent multimodal connectivity.
Brain 12/2007; 130(Pt 11):2929-41. · 9.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The functional status of central neural pathways, in particular their susceptibility to plasticity and functional reorganization, may influence speech performance of deaf cochlear implant users. In this paper, we sought to determine how brain metabolic activity measured before implantation relates to cochlear implantation outcome, that is, speech perception. In 22 prelingually deaf children between 1 and 11 years, we correlated preoperative glucose metabolism as measured by F-18 fluorodeoxyglucose positron emission tomography with individual speech perception performance assessed 3 years after implantation, while factoring out the confounding effect of age at implantation. Whereas age at implantation was positively correlated with increased activity in the right superior temporal gyrus, speech scores were selectively associated with enhanced metabolic activity in the left prefrontal cortex and decreased metabolic activity in right Heschl's gyrus and in the posterior superior temporal sulcus. These results reinforce the notion that implantation should be performed as early as possible to prevent cross-modal takeover of auditory regions and suggest that rehabilitation strategies may be more efficient if they capitalize on general cognitive functions instead of only targeting specialized circuits dedicated to auditory and audiovisual pattern recognition.
Cerebral Cortex 05/2007; 17(4):909-17. · 6.54 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cochlear implantation is an effective technique for restoring hearing in the profoundly deaf. Although cochlear implants are a therapeutical success, huge performance variability in speech comprehension is observed after implantation. The reason for this remains incompletely understood after 20 years of clinical practice and basic research. Which patients are going to respond well and why is an unresolved question. The duration of auditory deprivation plays an important role, and currently is the main predictor of implantation success in children; basically, the earlier the better. However, among patients with identical duration of deafness, performance remains highly variable, suggesting there are other more fundamental factors that determine clinical outcome.
To delineate the cognitive factors that could influence the clinical outcome of cochlear implantation, we correlated resting metabolism PET images acquired before implantation in congenitally deaf children with speech perception behavioural scores measured three years after implantation.
Using this paradigm, we showed distinct brain organisation patterns in the deaf brain, which predict good and bad speech perception outcome after cochlear implantation.
These data show that brain organisation assessed immediately before cochlear implantation can efficiently predict subsequent speech outcome.
Restorative neurology and neuroscience 02/2007; 25(3-4):381-90. · 2.51 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In congenitally deaf children, chronological age is generally accepted as a critical factor that affects successful rehabilitation following cochlear implantation (CI). However, a wide variance among patients is known to exist regardless of the age at CI [Sarant, J.Z., Blamey, P.J., Dowell, R.C., Clark, G.M., Gibson, W.P., 2001. Variation in speech perception scores among children with cochlear implants. Ear Hear. 22, 18-28]. In a previous study, we reported that prelingually deaf children in the age range 5-7 years at implantation showed greatest outcome variability [Oh S.H., Kim C.S., Kang E.J., Lee D.S., Lee H.J., Chang S.O., Ahn S.H., Hwang C.H., Park H.J., Koo J.W., 2003. Speech perception after cochlear implantation over a 4-year time period. Acta Otolaryngol. 123, 148-153]. Eleven children who underwent CI between the age of 5 and 7 1/2 years were subdivided into a good (above 65%: GOOD) and a poor (below 45%: POOR) group based on the performance in a speech perception test given 2 years after CI. The preoperative (18)F-FDG-PET (F-18 fluorodeoxyglucose positron emission tomography) images were compared between the two groups in order to examine if regional glucose metabolic difference preexisted before the CI surgery. In the GOOD group, metabolic activity was greater in diverse fronto-parietal regions compared to the POOR group. In the POOR group, the regions related to the ventral visual pathway showed greater metabolic activity relative to the GOOD group. These findings suggest that the deaf children who had developed greater executive and visuospatial functions subserved by the prefrontal and parietal cortices might be successful in auditory language learning after CI. On the contrary, greater dependency on the visual function subserved by the occipito-temporal region due to auditory deprivation may interfere with acquisition of auditory language after CI.
Hearing Research 06/2005; 203(1-2):2-9. · 2.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To propose management options for cochlear implantation in chronic otitis media based on our experiences.
A retrospective review of 418 cochlear implantations performed by the 2 senior authors between November 1988 and February 2004 was conducted. Nine patients who had chronic otitis media in the ear to be implanted were included. Of these, three showed active inflammation at presentation; the other six cases had undergone previous tympanomastoidectomy surgery and did not show active inflammation at presentation.
Five patients with active inflammation or without an adequate soft tissue layer in the mastoid bowl underwent a two-stage procedure. Four cases who showed inactive inflammation and had an adequate tissue layer to protect the electrode array underwent a single-stage technique, although two of them showed dry tympanic membrane perforation. No local or intracranial inflammation recurred. The electrode was exposed in the mastoid bowl in one case, who was managed with revisional mastoid obliteration with soft tissue.
Complete eradication of inflammation and the securing of a strong protective soft tissue layer over the electrode are prerequisites for cochlear implantation in ears with chronic otitis media.
Acta Oto-Laryngologica 11/2004; 124(9):1033-8. · 1.08 Impact Factor
-
Cochlear Implants International 10/2004; 5 Suppl 1:65-7.
-
Cochlear Implants International 10/2004; 5 Suppl 1:67-9.
-
Cochlear Implants International 10/2004; 5 Suppl 1:156-7.
-
Cochlear Implants International 08/2004; 5:65-67.
-
[show abstract]
[hide abstract]
ABSTRACT: The aim of this study was to report a series of 18 facial nerve schwannomas, including 2 infantile cases.
Retrospective case review.
Tertiary referral center.
Eighteen patients with facial nerve schwannoma, operated on between 1980 and 2000.
Surgical treatments were performed in all cases.
The presenting symptoms and facial nerve function were graded using the House-Brackmann scale and eye closure. RESULTS Facial nerve paralysis was the most common symptom, presenting in 94% of cases, followed by hearing loss and mass lesion. In one case, the tumor was shaved, leaving the facial nerve intact. In the other cases, the facial nerve reconstruction with hypoglossal-facial anastomosis or interposition graft was performed. The postoperative facial function was House-Brackmann grade IV in most cases (88.2%). In terms of the functional recovery classified by complete or incomplete eye closure, the moderate preoperative facial nerve palsy group showed a better functional outcome than severe group.
In cases with good facial nerve function, it would be better to consider an alternative method for preserving the facial nerve. Furthermore, when facial nerve paralysis has developed to more than House-Brackmann grade III, an immediate operation is recommended to obtain a good postoperative facial functional recovery.
Ontology & Neurotology 04/2003; 24(2):312-6. · 1.90 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To evaluate the long-term speech perception of cochlear implantees and to compare the developing auditory performance patterns of prelingual children and postlingual deaf adults.
Twenty-nine prelingually deaf children and 17 postlingually deaf adults who had been followed up for 4 years were included in the study. Speech perception ability was assessed by means of vowel and consonant confusion tests and the Korean version of the Central Institute of Deafness (K-CID) test (performed without visual cues). The test results were analyzed at 3 and 6 months after implantation and then annually.
In the prelingually deaf children, the average results continuously improved over the 4-year period. In the postlingually deaf adults, the average results did not improve further after the first 2 years. Individuals with < 5 years of deafness had a faster rate of recovery of speech perception than those who had been deaf for > 5 years. The K-CID scores were negatively correlated with age at implantation for the prelingually deaf group and with the duration of deafness in the postlingually deaf group. Children fitted with implants at a younger age showed better speech perception ability than those fitted with implants at an older age. Interestingly, prelingually deaf children aged 5-7 years at implantation showed the widest variation in individual outcomes. Amongst this group of children with highly variable outcomes, the metabolic status of brain cortices determined by means of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) was available for three patients. The individual with the widest hypometabolic area had the best speech perception ability.
The extent of hypometabolism as assessed by FDG-PET seemed to be one of the major factors predicting the outcome of cochlear implantation.
Acta Oto-Laryngologica 01/2003; 123(2):148-53. · 1.08 Impact Factor
-
Jin Su Kim,
Jae Sung Lee,
Min-Hyun Park,
Hyejin Kang,
Jong Jin Lee, Hyo-Jeong Lee,
Ki Chun Im,
Dae Hyuk Moon,
Sang-Moo Lim,
Seung-Ha Oh,
Dong Soo Lee
[show abstract]
[hide abstract]
ABSTRACT: The aim of this study was to establish the procedures for 3D voxel-based statistical analysis of 2-deoxy-2-[(18)F]fluoro-D-glucose-positron emission tomography (FDG-PET) images of a cat's brain obtained using a small animal-dedicated PET system and to assess the utility of this approach in investigating the cerebral glucose metabolism in an animal model of cortical deafness.
This study compared several different strategies for the spatial processing of PET data acquired twice from eight cats before and after inducing deafness in terms of the comparability of the statistical analysis results to the established pattern of the cerebral glucose metabolic changes in the deaf animals.
The accuracy of the spatial preprocessing procedures and the statistical significance of the comparison were improved by removing the background activities outside the brain regions. The use of the spatial normalization parameters obtained from the mean image of the realigned data set for individual data also helped improve the statistical significance of the paired t testing. It was also found that an adjustment of the registration options was also important for increasing the precision of the realignment.
A method for voxel-based analysis of the PET data of a cat's brain was optimized. The results demonstrated the high localization accuracy and specificity of this method, which is expected to be useful for examining the brain PET data of medium-sized animals such as cats.
Molecular Imaging & Biology 10(3):154-61. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A cerebrospinal fluid (CSF) gusher during cochlear implantation can produce surgical difficulties and postoperative life-threatening morbidities such as meningitis. We reviewed our experiences of managing CSF gush during cochlear implantation, and assessed the radiologic characteristics of a CSF gusher. Seventy-two congenital deaf children with inner ear malformation underwent cochlear implantation in Seoul National University Children's Hospital from November 1988 to March 2004. Among these, 15 patients showed CSF gush intraoperatively. Total or partial defect of the modiolus increased the risk of CSF gush significantly. Dilated vestibular aqueduct and bulbous IAC showed no statistical significance. During surgery, the mucosa around the cochleostomy opening was removed and soft tissue plugs were packed alongside the active electrodes. Some additional procedures such as mastoid or posterior tympanic obliteration were performed in three patients with intractable CSF gush. No lumbar drain was used. Postoperative meningitis developed in one case after 7 months of implant usage; however, there was no evidence of CSF leak in all cases during the postoperative follow-up (1–47 months, mean 22 months). Surgeons should be prepared to cope with CSF gusher during cochlear implantation in cases with congenital inner ear malformation, particularly if the patient has radiological evidence of modiolar defect.
International Congress Series.
