Minoo Lenarz

Publications of Minoo Lenarz

• Effect of gender on the hearing performance of adult cochlear implant patients.

  Authors: Minoo Lenarz, Hasibe Sönmez, Gert Joseph, Andreas Büchner, Thomas Lenarz

  The Laryngoscope. 02/2012;

  OBJECTIVES/HYPOTHESIS: To evaluate the role of gender on the hearing performance of postlingually deafened adult patients with cochlear implants. STUDY DESIGN: Individual retrospective cohort study.OBJECTIVES/HYPOTHESIS: To evaluate the role of gender on the hearing performance of postlingually deafened adult patients with cochlear implants. STUDY DESIGN: Individual retrospective cohort study. METHODS: There were 638 postlingually deafened adults (280 men and 358 women) selected for a retrospective evaluation of their hearing performance with cochlear implants. Both genders underwent the same surgical and rehabilitative procedures and benefited from the latest technological advances available. There was no significant difference in the age, duration of deafness, and preoperative hearing performance between the genders. The test battery was composed of the Freiburger Monosyllabic Test, Speech Tracking, and the Hochmair-Schulz-Moser (HSM) sentence test in quiet and in 10-dB noise. The results of 5 years of follow-up are presented here. RESULTS: Genders showed a similar performance in Freiburger Monosyllabic Test and Speech Tracking Test. However, in the HSM test in noise, men performed slightly better than women in all of the follow-up sessions, which was statistically significant at 2 and 4 years after implantation. CONCLUSIONS: Although normal-hearing women use more predictive cognitive strategies in speech comprehension and are supposed to have a more efficient declarative memory system, this may not necessarily lead to a better adaptation to the altered auditory information delivered by a cochlear implant. Our study showed that in more complex listening situations such as speech tests in noise, men tend to perform slightly better than women. Gender may have an influence on the hearing performance of postlingually deafened adults with cochlear implants.

• Long-Term Performance of Cochlear Implants in Postlingually Deafened Adults.

  Authors: Minoo Lenarz, Hasibe Sönmez, Gert Joseph, Andreas Büchner, Thomas Lenarz

  Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery. 02/2012;

  Objective. To evaluate the stability of long-term hearing performance after cochlear implantation (CI) in postlingually deafened adults and to explore the boundaries and limitations of the presentObjective. To evaluate the stability of long-term hearing performance after cochlear implantation (CI) in postlingually deafened adults and to explore the boundaries and limitations of the present test batteries for adult CI patients.Study Design. Case series with chart review.Setting. Tertiary referral center.Subjects and Methods. A cohort of 1005 postlingually deafened adult cochlear implantees, who received their implants after age 18 years, was unilaterally implanted and had no inner ear malformations or cochlear ossification. Hearing performance with cochlear implant was evaluated with the help of 5 standard German speech tests.Results. The average performance improved significantly during the first 6 months in all tests (learning phase) and afterward entered a plateau phase in which no statistically significant improvements or deteriorations were observed for more than 20 years of follow-up. For each test, the average performance of the cohort, the ceiling effect, and the average results for high and low performers are presented.Conclusions. In this study, postlingually deafened adults required about 6 months to learn how to process the artificial signals delivered by the cochlear implant. After this learning phase, the hearing performance entered a stable plateau phase for more than 20 years. This stability reveals the long-term reliability of the technology and the biological stability of the electrode-nerve interface over years. In this study, the authors also evaluated the "ceiling effect" with 5 standard German speech tests, used for evaluation of postlingually deafened adult CI patients.

• Cochlear implant performance in geriatric patients.

  Authors: Minoo Lenarz, Hasibe Sönmez, Gert Joseph, Andreas Büchner, Thomas Lenarz

  The Laryngoscope. 02/2012;

  OBJECTIVES/HYPOTHESIS: To evaluate the hearing performance with cochlear implants (CIs) in patients who were 70 years or older at the time of implantation (geriatric patients) and compare it with theOBJECTIVES/HYPOTHESIS: To evaluate the hearing performance with cochlear implants (CIs) in patients who were 70 years or older at the time of implantation (geriatric patients) and compare it with the performance in younger adults. STUDY DESIGN: Individual, retrospective, cohort study. METHODS: A cohort of 1,005 postlingually deafened adults was selected for this study. According to their age at the time of cochlear implantation, patients were divided into four age groups: group 1, 18 to 39 years; group 2, 40 to 59 years; group 3, 60 to 69 years; and group 4, 70 years and older). The test battery was composed of four standard German speech tests: Freiburger Monosyllabic Test, Speech Tracking Test, and Hochmair-Schulz-Moser (HSM) Sentence Test in quiet and in 10 dB noise. RESULTS: Geriatric patients showed a similar learning curve as the younger adults in the first 2 years after implantation. The direct comparison of speech perception in the Freiburger Monosyllabic Test, Speech Tracking Test, and HSM Test in quiet revealed no differences between the average performance of the geriatric patients and younger adults. However, in the HSM Test in noise, the performance of the geriatric group was significantly lower than the younger adults. CONCLUSIONS: Geriatric CI patients have a similar learning curve to younger adults, and in speech tests in quiet they show a comparable performance. However, their performance is significantly lower in noisy surroundings. This may be due to the central presbycusis in patients older than 70 years and should be taken into account in postoperative fitting of these patients. Further prospective studies are required to evaluate the role of special rehabilitation methods and cognitive training to improve the speech perception in noise in geriatric CI patients.

• Effect of technological advances on cochlear implant performance in adults.

  Authors: Minoo Lenarz, Gert Joseph, Hasibe Sönmez, Andreas Büchner, Thomas Lenarz

  The Laryngoscope. 12/2011; 121(12):2634-40.

  To evaluate the effect of technological advances in the past 20 years on the hearing performance of a large cohort of adult cochlear implant (CI) patients. Individual, retrospective, cohortTo evaluate the effect of technological advances in the past 20 years on the hearing performance of a large cohort of adult cochlear implant (CI) patients. Individual, retrospective, cohort study. According to technological developments in electrode design and speech-processing strategies, we defined five virtual intervals on the time scale between 1984 and 2008. A cohort of 1,005 postlingually deafened adults was selected for this study, and their hearing performance with a CI was evaluated retrospectively according to these five technological intervals. The test battery was composed of four standard German speech tests: Freiburger monosyllabic test, speech tracking test, Hochmair-Schulz-Moser (HSM) sentence test in quiet, and HSM sentence test in 10 dB noise. The direct comparison of the speech perception in postlingually deafened adults, who were implanted during different technological periods, reveals an obvious improvement in the speech perception in patients who benefited from the recent electrode designs and speech-processing strategies. The major influence of technological advances on CI performance seems to be on speech perception in noise. Better speech perception in noisy surroundings is strong proof for demonstrating the success rate of new electrode designs and speech-processing strategies. Standard (internationally comparable) speech tests in noise should become an obligatory part of the postoperative test battery for adult CI patients.

• Preoperative prediction of vestibular schwannoma's nerve of origin with posturography and electronystagmography.

  Authors: Hendrik Borgmann, Thomas Lenarz, Minoo Lenarz

  Acta oto-laryngologica. 05/2011; 131(5):498-503.

  Chances of hearing preservation are better in patients with vestibular schwannoma (VS) from the superior vestibular nerve (SVN) than from the inferior vestibular nerve (IVN). Pathologic posturographyChances of hearing preservation are better in patients with vestibular schwannoma (VS) from the superior vestibular nerve (SVN) than from the inferior vestibular nerve (IVN). Pathologic posturography and electronystagmography (ENG) findings are more common in schwannomas from the SVN compared with tumors from the IVN. In this way, computerized dynamic platform posturography (CDPP) and ENG contribute to predict the nerve of origin of VS and can be used indirectly as a prognostic factor for hearing preservation. To test whether preoperative CDPP or ENG results contribute to predict the nerve of origin in VS and also to evaluate the influence of the nerve of origin on hearing preservation. Eighty-nine patients with VS originating from the IVN and 22 patients with VS from the SVN were included. Hearing loss due to surgery was calculated on postoperative and preoperative audiograms. Caloric response was measured by ENG and condition 5 and 6 score were recorded by CDPP before surgery. Hearing loss due to surgery was significantly lower in patients with tumors from the SVN than from the IVN (p = 0.011). Pathologic results in preoperative ENG (p < 0.0001) and CDPP (p = 0.025) were significantly more frequent in subjects with SVN than with IVN schwannomas.

• Effects of pulse phase duration and location of stimulation within the inferior colliculus on auditory cortical evoked potentials in a guinea pig model.

  Authors: Anke Neuheiser, Minoo Lenarz, Guenter Reuter, Roger Calixto, Ingo Nolte, Thomas Lenarz, Hubert H Lim

  Journal of the Association for Research in Otolaryngology : JARO. 12/2010; 11(4):689-708.

  The auditory midbrain implant (AMI), which consists of a single shank array designed for stimulation within the central nucleus of the inferior colliculus (ICC), has been developed for deaf patientsThe auditory midbrain implant (AMI), which consists of a single shank array designed for stimulation within the central nucleus of the inferior colliculus (ICC), has been developed for deaf patients who cannot benefit from a cochlear implant. Currently, performance levels in clinical trials for the AMI are far from those achieved by the cochlear implant and vary dramatically across patients, in part due to stimulation location effects. As an initial step towards improving the AMI, we investigated how stimulation of different regions along the isofrequency domain of the ICC as well as varying pulse phase durations and levels affected auditory cortical activity in anesthetized guinea pigs. This study was motivated by the need to determine in which region to implant the single shank array within a three-dimensional ICC structure and what stimulus parameters to use in patients. Our findings indicate that complex and unfavorable cortical activation properties are elicited by stimulation of caudal-dorsal ICC regions with the AMI array. Our results also confirm the existence of different functional regions along the isofrequency domain of the ICC (i.e., a caudal-dorsal and a rostral-ventral region), which has been traditionally unclassified. Based on our study as well as previous animal and human AMI findings, we may need to deliver more complex stimuli than currently used in the AMI patients to effectively activate the caudal ICC or ensure that the single shank AMI is only implanted into a rostral-ventral ICC region in future patients.

• Auditory midbrain implant: a review.

  Authors: Hubert H Lim, Minoo Lenarz, Thomas Lenarz

  Trends in amplification. 09/2009; 13(3):149-80.

  The auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in deaf patients who cannot sufficiently benefit from cochlear implants. TheThe auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in deaf patients who cannot sufficiently benefit from cochlear implants. The authors have begun clinical trials in which five patients have been implanted with a single shank AMI array (20 electrodes). The goal of this review is to summarize the development and research that has led to the translation of the AMI from a concept into the first patients. This study presents the rationale and design concept for the AMI as well a summary of the animal safety and feasibility studies that were required for clinical approval. The authors also present the initial surgical, psychophysical, and speech results from the first three implanted patients. Overall, the results have been encouraging in terms of the safety and functionality of the implant. All patients obtain improvements in hearing capabilities on a daily basis. However, performance varies dramatically across patients depending on the implant location within the midbrain with the best performer still not able to achieve open set speech perception without lip-reading cues. Stimulation of the auditory midbrain provides a wide range of level, spectral, and temporal cues, all of which are important for speech understanding, but they do not appear to sufficiently fuse together to enable open set speech perception with the currently used stimulation strategies. Finally, several issues and hypotheses for why current patients obtain limited speech perception along with several feasible solutions for improving AMI implementation are presented.

• Artifacts caused by cochlear implants with non-removable magnets in 3T MRI: phantom and cadaveric studies.

  Authors: Omid Majdani, Thomas Rau, Friedrich Götz, Martin Zimmerling, Minoo Lenarz, Thomas Lenarz, Robert Labadie, Martin Leinung

  European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery. 08/2009;

  The aim of this study was to evaluate artifacts produced by cochlear implants (CI) during 3.0 Tesla (T) magnetic resonance imaging of the brain using different sequences on phantom and cadavericThe aim of this study was to evaluate artifacts produced by cochlear implants (CI) during 3.0 Tesla (T) magnetic resonance imaging of the brain using different sequences on phantom and cadaveric specimens. A phantom and three cadaveric specimens with CIs were imaged using a 3.0 T clinical scanner. Artifacts were analyzed quantitatively and according to the sequence used. Different brain regions were evaluated for image distortion and limitation of diagnostic significance. In cadaver studies, all sequences generated signal-void areas around the implant. In T2-weighted sequences, additional periodic shadowing was discovered. Anatomical structures of the brain on the contralateral side of the CI were for the most part undistorted. At 3T, artifacts around CIs with non-removable magnets compromise image quality of the nearby brain regions and diagnosis of brain lesions is limited. In the contralateral hemisphere, diagnostic accuracy is only marginally limited.

• Demagnetization of cochlear implants and temperature changes in 3.0T MRI environment.

  Authors: Omid Majdani, Martin Leinung, Thomas Rau, Arash Akbarian, Martin Zimmerling, Minoo Lenarz, Thomas Lenarz, Robert Labadie

  Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery. 01/2009; 139(6):833-9.

  OBJECTIVE: To investigate the level of demagnetization of the magnets and temperature changes in cochlear implants (Cis) in a 3.0 tesla (3.0T) MRI. STUDY DESIGN: Experimental. SUBJECTS AND METHODS:OBJECTIVE: To investigate the level of demagnetization of the magnets and temperature changes in cochlear implants (Cis) in a 3.0 tesla (3.0T) MRI. STUDY DESIGN: Experimental. SUBJECTS AND METHODS: Demagnetization and remagnetization measurements were done on magnets for different types of CIs. Temperature of different body and electrode sides was measured in the MRI environment. RESULTS: Demagnetization of the magnets of the CI is dependent on the angle between the magnetic field of the CI magnet and the MRI. When this angle was greater than 80 degrees, relevant demagnetization occurred and sufficient remagnetization was not possible with the 3.0T MRI magnet. Maximum temperature rise was 0.5 degrees C. CONCLUSIONS: Patients carrying CIs with non-removable magnets should not enter a 3.0T MRI device in a routine clinical setup. Under special conditions (angle between the two magnets less than 80 degrees) imaging in a 3.0T MRI may be possible without harming the patient or the implant.

• Intratympanic membrane cholesteatoma after tympanoplasty with the underlay technique.

  Authors: Mohammad Nejadkazem, Javad Totonchi, Masood Naderpour, Minoo Lenarz

  Archives of otolaryngology--head & neck surgery. 06/2008; 134(5):501-2.

  OBJECTIVE: To evaluate the incidence of intratympanic membrane cholesteatoma (ITMC) in patients after tympanoplasty with the underlay technique. DESIGN: Retrospective study. SETTING: Ear, nose, andOBJECTIVE: To evaluate the incidence of intratympanic membrane cholesteatoma (ITMC) in patients after tympanoplasty with the underlay technique. DESIGN: Retrospective study. SETTING: Ear, nose, and throat department, Tabriz University of Medical Sciences, Tabriz, Iran. PATIENTS: A total of 1121 patients with central tympanic membrane perforation were evaluated after tympanoplasty. INTERVENTIONS: Tympanoplasty was performed with the underlay technique using temporal facial graft. MAIN OUTCOME MEASURE: The patients were followed up to assess the postoperative incidence of ITMC. RESULTS: During the follow-up period of 5 years, ITMC was observed in 9 patients (0.8%). Of these 9 patients, 8 were asymptomatic and had intact tympanic membranes. The asymptomatic cases were detected 1 to 2 years after surgery during routine follow-up examinations. Only 1 of 9 patients had otorrhea, which was due to a posterior perforation away from the location of the ITMC. The most common site of the ITMC was near the umbo. CONCLUSIONS: Even after tympanoplasty with underlay technique, ITMC may develop between the layers of the tympanic membrane. The most common location of these cholesteatomas is near the umbo, which may be the result of insufficient removal of the residual squamous epithelium from the handle of the malleus. The cholesteatomas are usually asymptomatic and can be detected during routine follow-up examinations 1 to 2 years after surgery. Although ITMCs are usually noninvasive in nature, a review of the literature revealed that in rare cases they can also show a rapid and invasive growth pattern. Early detection and removal of these asymptomatic cholesteatomas during routine postoperative follow-up examinations can prevent their progression as well as consequent residual problems and complications.

• Extra- and intracranial dumbbell-shaped hemangiopericytoma.

  Authors: Marc Diensthuber, Friedrich Götz, Florian Länger, Thomas Lenarz, Minoo Lenarz

  European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery. 05/2008; 265(4):481-4.

  Hemangiopericytomas are malignant tumors arising from pericytic cells and account for less than 1% of all vascular neoplasms. We report a rare case of an extra- and intracranial dumbbell-shapedHemangiopericytomas are malignant tumors arising from pericytic cells and account for less than 1% of all vascular neoplasms. We report a rare case of an extra- and intracranial dumbbell-shaped hemangiopericytoma originating from the soft tissue of the neck and penetrating the skull base with invasion into the posterior cranial fossa. The 59-year-old female patient presented with a large pulsating neck mass and reported weakness, abnormal fatigue and headache. MRI revealed an inhomogeneously enhancing tumor and cerebral angiography showed intensive vascularization. Preoperative embolization was performed in order to decrease the operative blood loss. The tumor was operated via a far lateral approach through an osteoclastic suboccipital craniotomy. Total resection of both the intra- and extracranial part of the neoplasm (grade I by Simpson) could be achieved. The histopathological analysis revealed a mesenchymal, hypervascular tumor with the classic staghorn vascular pattern. In this article, we discuss the clinical presentation and multidisciplinary management of hemangiopericytoma and describe the radiological and pathological features of this tumor entity.

• A comparative study of the audiological outcomes with Retro-X (semi-implantable hearing aid system) and conventional open fitting hearing aids.

  Authors: Minoo Lenarz, Thomas Lenarz, Martin Stieve, Mark Winter

  European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery. 04/2008;

  The objective of this study was to compare the results of hearing augmentation with the Retro-X semi-implantable hearing aid to a conventional non-implantable open canal hearing aid using the sameThe objective of this study was to compare the results of hearing augmentation with the Retro-X semi-implantable hearing aid to a conventional non-implantable open canal hearing aid using the same software technology (Titan-X, auric Hearing Systems, HiKaNo.:13.20.03.0047). Nineteen subjects (20 ears) with mild to moderate high-frequency sensory-neural hearing loss were included in this clinical study. All the subjects were first fitted with a conventional open canal hearing aid (Titan-X). After a period of 4-6 weeks audiological evaluations were performed using standardized speech tests in quiet and noise. Subjective evaluation was performed with the help of standardized questionnaires. After this phase the patients received the semi-implantable Retro-X device under local anaesthesia and 4 weeks later were fitted with a hearing module with the same software technology as the conventional Titan-X hearing aid. Four weeks following the first fitting the same audiological evaluations were performed under similar conditions and the patients were evaluated again using the same questionnaires in order to compare the results of the Retro-X semi-implantable system with the conventional open canal hearing aid. Audiological evaluations revealed better results with the semi-implantable Retro-X in the adaptive speech in noise test; however, the results of the monosyllabic word test in quiet were similar for the Retro-X and conventional open canal hearing aid. The patients subjectively preferred the improved wearing comfort of the semi-implantable device. The Retro-X semi-implantable hearing aid provides better speech perception in noise and higher wearing comfort in comparison to the conventional open canal hearing aids. Considering the simple implantation procedure under local anaesthesia with low complication rate, Retro-X is an alternative to the conventional open canal hearing aids in patients with mild to moderate high frequency sensory-neural hearing loss.

• A true minimally invasive approach for cochlear implantation: high accuracy in cranial base navigation through flat-panel-based volume computed tomography.

  Authors: Omid Majdani, Soenke H Bartling, Martin Leinung, Timo Stöver, Minoo Lenarz, Christian Dullin, Thomas Lenarz

  Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 03/2008; 29(2):120-3.

  OBJECTIVE: High-precision intraoperative navigation using high-resolution flat-panel volume computed tomography makes feasible the possibility of minimally invasive cochlear implant surgery,OBJECTIVE: High-precision intraoperative navigation using high-resolution flat-panel volume computed tomography makes feasible the possibility of minimally invasive cochlear implant surgery, including cochleostomy. Conventional cochlear implant surgery is typically performed via mastoidectomy with facial recess to identify and avoid damage to vital anatomic landmarks. To accomplish this procedure via a minimally invasive approach--without performing mastoidectomy--in a precise fashion, image-guided technology is necessary. With such an approach, surgical time and expertise may be reduced, and hearing preservation may be improved. INTERVENTIONS: Flat-panel volume computed tomography was used to scan 4 human temporal bones. A drilling channel was planned preoperatively from the mastoid surface to the round window niche, providing a margin of safety to all functional important structures (e.g., facial nerve, chorda tympani, incus). MAIN OUTCOME MEASURES: Postoperatively, computed tomographic imaging and conventional surgical exploration of the drilled route to the cochlea were performed. RESULTS: All 4 specimens showed a cochleostomy located at the scala tympani anterior inferior to the round window. The chorda tympani was damaged in 1 specimen--this was preoperatively planned as a narrow facial recess was encountered. CONCLUSION: Using flat-panel volume computed tomography for image-guided surgical navigation, we were able to perform minimally invasive cochlear implant surgery defined as a narrow, single-channel mastoidotomy with cochleostomy. Although this finding is preliminary, it is technologically achievable.

• The auditory midbrain implant: Effects of electrode location.

  Authors: Hubert H Lim, Thomas Lenarz, David J Anderson, Minoo Lenarz

  Hearing research. 03/2008;

  The auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in patients who do not receive sufficient benefit from cochlear or brainstemThe auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in patients who do not receive sufficient benefit from cochlear or brainstem prostheses. We have begun clinical trials in which three patients have been implanted with the AMI. Although the intended target was the central nucleus of the inferior colliculus (ICC), the electrode array was implanted into different locations across patients (i.e., ICC, dorsal cortex of inferior colliculus, lateral lemniscus). In this paper, we will summarize the effects of electrical stimulation of these different midbrain regions on various psychophysical properties and speech perception performance. The patient implanted within the intended target, the ICC, exhibited the greatest improvements in hearing performance. However, this patient has not yet achieved open-set speech perception to the performance level typically observed for cochlear implant patients, which we believe is partially due to the location of the array within the ICC. We will present findings from previous AMI studies in guinea pigs demonstrating the existence of spatially distinct functional output regions within the ICC and suggesting that further improvements in performance may be achieved by stimulating within a rostral-ventral region. Remaining questions include if a similar organization exists in the human ICC and if stimulation of its rostral-ventral region with currently available strategies (i.e., those designed for cochlear implants) can restore sufficient speech perception.

• Auditory midbrain implant: histomorphologic effects of long-term implantation and electric stimulation of a new deep brain stimulation array.

  Authors: Minoo Lenarz, Hubert H Lim, Thomas Lenarz, Uta Reich, Nadine Marquardt, Marc N Klingberg, Gerrit Paasche, Günter Reuter, Alexandru C Stan

  Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 01/2008; 28(8):1045-52.

  HYPOTHESIS: Chronic implantation and electric stimulation with a human prototype auditory midbrain implant (AMI) array within the inferior colliculus achieves minimal neuronal damage and does notHYPOTHESIS: Chronic implantation and electric stimulation with a human prototype auditory midbrain implant (AMI) array within the inferior colliculus achieves minimal neuronal damage and does not cause any severe complications. BACKGROUND: An AMI array has been developed for patients with neural deafness and, based on animal studies, has shown to possess potential as an auditory prosthesis in humans. To investigate the safety of the AMI for clinical use, we characterized the histomorphologic effects of chronic implantation and stimulation within its target structure, the inferior colliculus. METHODS: Eight cats were chronically implanted for 3 months, and histologic sections were analyzed to assess long-term tissue effects. Four of the 8 cats were additionally stimulated for 60 days (4 h/d) starting 4 weeks after implantation to assess if clinically relevant stimuli further affected the tissue response. RESULTS: In general, both neurons and neuropil surrounding the implant track were apparently unaffected, whereas a fibrillary sheath (approximately 50 microm thick) developed around the array. There was a significant decrease in neuron density 50 to 100 microm away from the track with a significantly elevated number of glial cells out to approximately 250 to 350 microm. Chronic stimulation seemed to improve the tissue response and neuronal survival around the implant, although further studies are needed to confirm this finding. CONCLUSION: The histomorphologic effects and extent of neuronal damage observed for our AMI array are similar to those of other neural implants currently and safely used in humans. The minimal tissue damage surrounding the implanted array is encouraging with regard to the safety of the array for human use.

• Electrical stimulation of the midbrain for hearing restoration: insight into the functional organization of the human central auditory system.

  Authors: Hubert H Lim, Thomas Lenarz, Gert Joseph, Rolf-Dieter Battmer, Amir Samii, Madjid Samii, James F Patrick, Minoo Lenarz

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 01/2008; 27(49):13541-51.

  The cochlear implant can restore speech perception in patients with sensorineural hearing loss. However, it is ineffective for those without an implantable cochlea or a functional auditory nerve.The cochlear implant can restore speech perception in patients with sensorineural hearing loss. However, it is ineffective for those without an implantable cochlea or a functional auditory nerve. These patients can be implanted with the auditory brainstem implant (ABI), which stimulates the surface of the cochlear nucleus. Unfortunately, the ABI has achieved limited success in its main patient group [i.e., those with neurofibromatosis type 2 (NF2)] and requires a difficult surgical procedure. These limitations have motivated us to develop a new hearing prosthesis that stimulates the midbrain with a penetrating electrode array. We recently implanted three patients with the auditory midbrain implant (AMI), and it has proven to be safe with minimal movement over time. The AMI provides loudness, pitch, temporal, and directional cues, features that have shown to be important for speech perception and more complex sound processing. Thus far, all three patients obtain enhancements in lip reading capabilities and environmental awareness and some improvements in speech perception comparable with that of NF2 ABI patients. Considering that our midbrain target is more surgically exposable than the cochlear nucleus, this argues for the use of the AMI as an alternative to the ABI. Fortunately, we were able to stimulate different midbrain regions in our patients and investigate the functional organization of the human central auditory system. These findings provide some insight into how we may need to stimulate the midbrain to improve hearing performance with the AMI.

• Primary central nervous system lymphoma presenting as bilateral tumors of the internal auditory canal.

  Authors: Minoo Lenarz, Martin Durisin, Hartmut Becker, Thomas Lenarz, Mohamad Nejadkazem

  Skull base : official journal of North American Skull Base Society ... [et al.]. 12/2007; 17(6):409-12.

  The increasing incidence of central nervous system (CNS) lymphoma in the general population, especially in young adults with AIDS, should alert the otolaryngologist that in future there will be anThe increasing incidence of central nervous system (CNS) lymphoma in the general population, especially in young adults with AIDS, should alert the otolaryngologist that in future there will be an even greater incidence of this rare disease. It may be responsible for hearing loss accompanied by other neurological deficits. CNS lymphoma often has a rapidly progressive course. Early diagnosis and rapid therapy are crucial for a better prognosis. We report a case of primary CNS lymphoma involving both internal auditory canals that presented with sudden deafness and disequilibrium accompanied by facial and abducens nerve palsy.

• Cavernous hemangioma of the internal auditory canal.

  Authors: Minoo Lenarz, Martin Durisin, Petr Kamenetzki, Hartmut Becker, Hans-Heinrich Kreipe, Thomas Lenarz

  European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery. 06/2007; 264(5):569-71.

  Hemangiomas rarely occur in the internal auditory canal. These tumors originate from the capillary bed of the epineurium surrounding the nerve and can either compress or infiltrate the nerve.Hemangiomas rarely occur in the internal auditory canal. These tumors originate from the capillary bed of the epineurium surrounding the nerve and can either compress or infiltrate the nerve. Depending on location and the nerve of origin, these lesions can cause severe and progressive sensorineural hearing loss, tinnitus, facial nerve palsy, or vertigo even when they are relatively small. The presence of a small contrast-enhancing tumor in the internal auditory canal accompanied by severe sensorineural hearing loss and facial nerve palsy, should raise the suspicion of a hemangioma. Early recognition and surgical intervention in these benign tumors may improve the chance of preserving the functional integrity of the facial nerve and provides better results after nerve reconstruction. Due to their relative small size, the temporal bone CT-scan may show no evidence of pathological widening of the internal auditory canal or the typical intralesional calcifications at the time of presentation. MRI with Gadolinium is the imaging method of choice and a high index of clinical suspicion is necessary for the diagnosis of these tumors. In this paper we report about a 51-year-old male presented with right-sided sensory-neural deafness and facial nerve palsy, accompanied by severe tinnitus and ipsilateral loss of vestibular function due to a cavernous hemangioma in the internal auditory canal.

• A case of multiple primary tumors of the anterior skull base.

  Authors: Minoo Lenarz, Martin Durisin, Hartmut Becker, Almuth Brandis, Thomas Lenarz

  Skull base : official journal of North American Skull Base Society ... [et al.]. 04/2007; 17(2):153-6.

  We report a case of synchronous olfactory bulb meningioma and undifferentiated carcinoma of the nose and paranasal sinuses that involved and destroyed the anterior skull base and mimickedWe report a case of synchronous olfactory bulb meningioma and undifferentiated carcinoma of the nose and paranasal sinuses that involved and destroyed the anterior skull base and mimicked intracranial invasion by a carcinoma. The heterogeneity of tissue types in the skull base gives rise to a diverse variety of benign and malignant neoplasms which have totally different prognoses. Synchronous development of benign and malignant primary tumors both originating from and involving the skull base at the same location is very rare and may cause confusion for both the skull base surgeon and neuroradiologist.

• Auditory midbrain implant: a combined approach for vestibular schwannoma surgery and device implantation.

  Authors: Amir Samii, Minoo Lenarz, Omid Majdani, Hubert H Lim, Madjid Samii, Thomas Lenarz

  Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 02/2007; 28(1):31-8.

  HYPOTHESIS: The lateral suboccipital approach is a well-established route for safe removal of vestibular schwannomas in neurofibromatosis Type 2 (NF2) patients. The goal of this study was to assessHYPOTHESIS: The lateral suboccipital approach is a well-established route for safe removal of vestibular schwannomas in neurofibromatosis Type 2 (NF2) patients. The goal of this study was to assess if this approach can be extended to a lateral supracerebellar infratentorial approach to enable insertion of an auditory midbrain implant (AMI) penetrating array along the tonotopic gradient of the inferior colliculus central nucleus (ICC). BACKGROUND: The AMI is a new auditory prosthesis designed for penetrating stimulation of the ICC in patients with neural deafness. The initial candidates are NF2 patients who, because of the growth and/or surgical removal of bilateral acoustic neuromas, develop neural deafness and are unable to benefit from cochlear implants. The ideal surgical approach in NF2 patients must first enable safe removal of vestibular schwannomas and then provide sufficient exposure of the midbrain for AMI implantation. METHODS: This study was performed on formalin-fixed and fresh cadaver specimens. Computed tomography scan and magnetic resonance imaging were used to study the heads of the specimens and for surgical navigation. RESULTS: The lateral suboccipital craniotomy enabled sufficient exposure of the cerebellopontine angle and internal auditory canal for tumor removal. It could then be extended to a lateral supracerebellar infratentorial approach that provided good exposure of the dorsolateral aspect of the tentorial hiatus and mesencephalon for implantation of the AMI along the tonotopic gradient of the ICC. This approach did not endanger the trochlear nerve or any major midline venous structures in the quadrigeminal cistern. CONCLUSION: This modified lateral suboccipital approach ensures safe removal of large vestibular schwannomas and provides sufficient exposure of the inferior colliculus for ideal AMI implantation.