Cochlear implantation in an animal model documents cochlear damage at the tip of the implant / Implante coclear em um modelo animal documenta o dano coclear na extremidade do implante

Abstract Introduction: Electrocochleography has recently emerged as a diagnostic tool in cochlear implant surgery, purposing hearing preservation and optimal electrode positioning. Objective: In this experimental study, extra-cochlear potentials were obtained during cochlear implant surgery in guinea pigs. The aim was to determine electrophysiological changes indicating cochlear trauma after cochleostomy and after electrode implantation in different insertion depths. Methods: Normal-hearing guinea pigs (n = 14) were implanted uni- or bilaterally with a multichannel electrode. The extra-cochlear cochlear nerve action potentials were obtained in response to acoustic stimuli at specific frequencies before and after cochleostomy, and after introduction of the electrode bundle. After the electrophysiological experiments, the guinea pigs were euthanized and microtomography was performed, in order to determine the position of the electrode and to calculate of the depth of insertion. Based on the changes of amplitude and thresholds in relation to the stimulus frequency, the electrophysiological data and the position obtained by the microtomography reconstruction were compared. Results: Cochleostomy promoted a small electrophysiological impact, while electrode insertion caused changes in the amplitude of extra-cochlear electrophysiological potentials over a wide range of frequencies, especially in the deepest insertions. There was, however, preservation of the electrical response to low frequency stimuli in most cases, indicating a limited auditory impact in the intraoperative evaluation. The mean insertion depth of the apical electrodes was 5339.56 μm (±306.45 - 6 inserted contacts) and 4447.75 μm (±290.23 - 5 inserted contacts). Conclusions: The main electrophysiological changes observed during surgical procedures occurred during implantation of the electrode, especially the deepest insertions, whereas the cochleostomy disturbed the potentials to a lesser extent. While hearing loss was often observed apical to the cochlear implant, it was possible to preserve low frequencies after insertion. © 2020 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Resumo Introdução: A eletrococleografia surgiu recentemente como uma ferramenta diagnóstica na cirurgia de implante coclear, objetiva a preservação da audição e o posicionamento ideal dos eletrodos. Objetivo: Determinar as alterações eletrofisiológicas indicativas de trauma coclear após a cocleostomia e após o implante do eletrodo em diferentes profundidades de inserção. Método: Neste estudo experimental, potenciais extracocleares foram obtidos durante a cirurgia de implante coclear em cobaias. Cobaias com audição normal (n = 14) foram implantadas uni- ou bilateralmente com eletrodo multicanal. Os potenciais de ação do nervo coclear extracoclear foram obtidos em resposta a estímulos acústicos em frequências específicas antes e após a cocleostomia e após a introdução do feixe de eletrodos. Após os experimentos eletrofisiológicos, as cobaias foram submetidas à eutanásia e a microtomografia foi feita para determinar a posição do eletrodo e calcular a profundidade de inserção. Com base nas mudanças de amplitude e limiares em relação à frequência do estímulo, os dados eletrofisiológicos e a posição obtida na reconstrução microtomográfica foram comparados. Resultados: A cocleostomia promoveu um pequeno impacto eletrofisiológico, enquanto a inserção do eletrodo causou alterações na amplitude dos potenciais eletrofisiológicos extra-cocleares em uma ampla faixa de frequências, especialmente nas inserções mais profundas. Houve, entretanto, preservação da resposta elétrica aos estímulos de baixa frequência na maioria dos casos, indicou um impacto auditivo limitado na avaliação intraoperatória. A profundidade média de inserção dos eletrodos apicais foi 5339,56 μm (± 306,45 - 6 contatos inseridos) e 4447,75 μm (± 290,23 - 5 contatos inseridos). Conclusão: As principais alterações eletrofisiológicas observadas durante os procedimentos cirúrgicos ocorreram durante o implante do eletrodo, especialmente nas inserções mais profundas, enquanto a cocleostomia alterou os potenciais em menor grau. Embora a perda auditiva seja frequentemente observada em posição apical ao implante coclear, foi possível preservar as baixas frequências após a inserção.

Hearing Preservation with the Transcrusal Approach to the Skull Base Lesion Combined with Other Transcranial Approach: Results of Consecutive Series of 5 Cases / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: This study reviewed our experience and outcomes of surgery via transcrusal approach to the skull base lesions. SUBJECTS AND METHOD: We performed transcrusal approach technique on five patients with skull base lesions (Cavernous malformation, Petroclival meningioma, Craniopharyngioma, Anaplastic astrocytoma, and Trigerminal epidermoid cyst) aiming at preserving hearing. Pre-and post-operative pure tone audiometry (PTA) and caloric test were performed in all patients. The transcrusal approach technique was performed as reported in the previous references. The approach included trephination of the superior and posterior semicircular canals from the ampullae to the common crus. The main outcome of this study was preserving hearing and the vestibular function after surgery, which was determined by PTA and caloric test. RESULTS: The average diameter of skull base lesion of the five patients was 3.68 cm. The mean follow up period was 114.2 days. The pre-operative mean PTA of five patients was 11 dB. The mean PTA of five patients within seven days after surgery was 28 dB. The last measured mean PTA was 29.8 dB. The pre and post-operative caloric results measured revealed vestibular function deficit in all of the patients after surgery (mean decreased value: 64%). All patients were stable during the surgery. Complications included two cerebrospinal fluid leak (40%) and one cranial VI nerve deficit (20%). CONCLUSION: Transcrusal approach is a method that can simultaneously preserve hearing and afford enough exposure of the skull base lesion if appropriately combined with other transcranial approach. We performed transcrusal approach targeting skull base lesion with hearing preservation, and we found excellent hearing result with this technique.

Residual Hearing Preservation with the Evo® Cochlear Implant Electrode Array: Preliminary Results

Abstract Introduction The preservation of residual hearing is currently an important challenge for cochlear implant surgeries. Indeed, if patients exhibit functional hearing after cochlear implantation, they can benefit from the combination of acoustical stimulation, usually in the low-frequencies and electrical stimulation in the high-frequencies. This combined mode of stimulation has proven to be beneficial both in terms of speech perception and of sound quality. Finding the right procedures for conducting softsurgeries and designing electrode arrays dedicated to hearing preservation is an open issue. Objective The objective of this study is to evaluate the combination of a soft-surgery procedure implicating round-window insertion and the use of dexamethasone and hyaluronic acid during surgery, with the use of a specifically designed straight soft electrode array, on hearing preservation in patients with functional hearing in the low frequencies. Methods This pre-clinical trial was conducted on seven patients with residual hearing in the low frequencies. The surgical method used employed a round window insertion and the use of topical dexamethasone. Results The soft-surgery protocol could be successfully followed in five patients. In this group, the average hearing threshold shift compared with pre-operative values was of 18.7 þ/ 16.1 dB HL up to 500 Hz and 15.7 þ/ 15.1 up to 1 kHz, demonstrating satisfying levels of hearing preservation. Conclusion We were able to demonstrate the possibility of preserving residual hearing in most of the patients using the EVO electrode. Significant residual hearing preservation levels were was obtained when a soft surgical approach involving round window insertion, dexamethasone and hyaluronic use during the surgery.

Surgical exposure of the internal auditory canal through the retrosigmoid approach with semicircular canals anatomical preservation / Avaliação da exposição do fundo do conduto auditivo interno através do acesso retrosigmóide-transmeatal

Objective Evaluate the feasibility of an adequate exposure with anatomical preservation of labyrinth structures through retrosigmoid transmeatal approach (RSA) in surgeries for resection of acoustic neuromas/vestibular schwannomas (VS). Method Thirty patients underwent surgical resection and were preoperatively evaluated with fine slice high definition CT scans and 3D-MRI volumetric reconstructions. Extension of internal auditory canal (IAC) opening during surgery was measured using 3 mm right-angle calibrated hook and neuronavigation parameters. Postoperatively, the extension of IAC opening and integrity of the labyrinth were confirmed through preoperatively images procedures. Results The preoperative length of IACs varied between 7.8 and 12.0 mm (mean 9.3 mm, SD 0.98, 95%CI 8.9 to 9.6, and median 9.0 mm). Postoperative images demonstrated adequate opening of the IAC and semicircular channels integrity. Conclusion A complete drilling of the posterior wall of IAC through the RSA is feasible and allows direct visualization of the IAC-fundus without damaging the semicircular canals. .

Objetivo Avaliar a possibilidade de exposição adequada preservando anatomia das estruturas labirínticas pelo acesso retrosigmóide-transmeatal (RSA) nas ressecções de schwannomas do vestibular (VS). Método Trinta pacientes foram submetidos à ressecção cirúrgica e avaliados no pré-operatório com tomografias de alta definição e reconstruções de ressonância magnética 3D. A extensão da abertura do conduto auditivo interno (CAI) foi medida e confirmada com parâmetros de neuronavegação. No pós-operatório, a extensão da abertura e a integridade do labirinto foram confirmadas por imagens de tomografia computadorizada. Resultados A extensão do CAI no pré-operatório apresentou variação de 7,8-12 mm (média 9,3 mm, DP 0,98, IC95% de 8,9-9,6 e mediana 9 mm). Imagens pós-operatórias demonstraram abertura adequada do IAC e integridade dos canais semicirculares. Conclusão A abertura completa da parede posterior do CAI pelo RSA é possível e permite a visualização direta do fundo do conduto sem prejudicar os canais semicirculares. .

Gamma Knife Radiosurgery for Vestibular Schwannomas

Vestibular schwannoma (VS) is a benign tumor typically originated in the schwann cell of vestibular nerve and usually accompany hearing symptom. Microsurgical removal and radiosurgery have a great role for the treatment of VS. Recently radiosurgery has been considered as an alternative or primary treatment for VS with the tremendous increase of patients who were treated with gamma knife radiosurgery (GKS) though microsurgery still takes the premier. By many published results, it is proved that GKS is a effective and noninvasive technique for VS, especially small sized tumors with satisfactory tumor control rate. The authors assumed that GKS can be expected to achieve satisfactory tumor control rate for small VS under 5 cc in volume. A major interest regarding radiosurgery nowadays is to determine the optimal radiation dose for hearing preservation to improve the quality of life of patients. The more high radiation dose are used for effective tumor growth control, the more radiation-related complications like as hearing deficit, the impairment of other cranial nerve function are increased. Since 1990's the mean radiation dose for tumor margin was more than 18 Gy, but there were high complication rate in spite of good tumor growth control. After the year of 2000, under the influence of advanced neuro-imaging techniques and radiosurgical planning system which enable clinicians to do more precise planning, marginal dose for VS has been decreased to 12-13 Gy and the radiation-related complications has been reduced. But because there may be a unexpected radiationinduced complications as time goes by after the latency period, optimal radiation dose for VS should be established on the basis of more long term follow-up observation.

Gamma Knife Radiosurgery for Vestibular Schwannomas

Vestibular schwannoma (VS) is a benign tumor typically originated in the schwann cell of vestibular nerve and usually accompany hearing symptom. Microsurgical removal and radiosurgery have a great role for the treatment of VS. Recently radiosurgery has been considered as an alternative or primary treatment for VS with the tremendous increase of patients who were treated with gamma knife radiosurgery (GKS) though microsurgery still takes the premier. By many published results, it is proved that GKS is a effective and noninvasive technique for VS, especially small sized tumors with satisfactory tumor control rate. The authors assumed that GKS can be expected to achieve satisfactory tumor control rate for small VS under 5 cc in volume. A major interest regarding radiosurgery nowadays is to determine the optimal radiation dose for hearing preservation to improve the quality of life of patients. The more high radiation dose are used for effective tumor growth control, the more radiation-related complications like as hearing deficit, the impairment of other cranial nerve function are increased. Since 1990's the mean radiation dose for tumor margin was more than 18 Gy, but there were high complication rate in spite of good tumor growth control. After the year of 2000, under the influence of advanced neuro-imaging techniques and radiosurgical planning system which enable clinicians to do more precise planning, marginal dose for VS has been decreased to 12-13 Gy and the radiation-related complications has been reduced. But because there may be a unexpected radiationinduced complications as time goes by after the latency period, optimal radiation dose for VS should be established on the basis of more long term follow-up observation.

Hearing Outcome after Gamma Knife Stereotactic Radiosurgery in Vestibular Schwannoma Patients with Serviceable Hearing

OBJECTIVE: The authors conducted a retrospective study to evaluate the preservation rates of serviceable hearing and to determine its prognostic factors after gamma knife stereotactic radiosurgery(GK SRS) in the patient with vestibular schwannomas. METHODS: Between December 1997 and March 2005, 54 patients with a sporadic vestibular schwannoma and serviceable hearing (Gardner Robertson grade I-II) were enrolled in this study. Electronic database of medical records and radiological examinations before and after GK SRS were investigated to the last follow up. The mean marginal dose was 12.3+/-0.7Gy. The mean maximum dose delivered to the tumor center was 24.7Gy (22~30Gy). The median tumor volume was 2cc (0.1~9.1cc). The median follow-up period of magnetic resonance(MR) imaging was 31 months (6~99 months), and the mean follow-up period of audiometry was 24 months (4~70 months). RESULTS: The tumor control rate was 100% in the patients with the follow up period more than 2 years. The trigeminal and facial nerve preservation rates were 98% and 100%, respectively. Twenty-eight (52%) of the 54 patients preserved serviceable hearing and 16 (30%) patients retained their pre-GK G-R grade level after GK SRS. In the univariate and multivariate analysis, there was no significant prognostic factor in preservation of the serviceable hearing. CONCLUSION: The hearing preservation rate is still unsatisfactory compared with the results of other cranial nerve preservation and tumor control in the treatment of vestibular schwannoma by GK SRS. More sophisticated strategy during and after GK SRS is necessary to improve long-term hearing preservation.

Hearing preservation and surgical complications after extended middle cranial fossa approach / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The advent of magnetic resonance imaging has enabled surgeons to detect small intracanalicular tumors. Therefore, many patients with acoustic tumors can be candidates for hearing preservation. This study was designed to analyze hearing results following acoustic tumor removal through the extended middle cranial fossa approach (EMCFA) and to determine the prognostic factors associated with successful hearing preservation. MATERIALS & METHODS: We retrospectively reviewed 11 patients whose tumor was removed via EMCFA (10:acoustic tumor, 1:lymphangioma). RESULTS: In 9 patients, the tumors were completely removed with EMCFA and in one patient, the suboccipital approach was combined with EMCFA. However, the approach was transformed to the translabyrinthine approach in one patient, because the tumor adhered to the cochlear nerve. The overall success rate of hearing preservation was 60% (6 of 10). In 20% of patients, the hearing was worse and other 20% of patients lost their hearing. Preoperative hearing level, location of tumor and origin of tumor affect the postoperative hearing. But tumor size did not relate to hearing preservation. CONCLUSION: In most cases, we could preserve the patient's hearing with EMCFA. However, the patients with poor preoperative hearing and tumor originated from the superior vestibular nerve were at risk for hearing loss.

Decision Analysis in Diagnosis of Small Acoustic Tumors / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: With great development that took place in the last 10 years in the imaging techniques such as MRI with gadolinium, small acoustic tumors can be detected before significant symptoms have developed. However, suspicion of acoustic neuroma is not easy at its earlier stage due to the lack of its characteristic symptoms. The detection rate of acoustic neuroma using traditional audiologic methods such as ABR and pure tone audiogram with speech discrimination score is relatively low contrary to expectation. Therefore, there is a need to develop other methods of diagnosis at an earlier stage. The aim of this study was to review symptomatology, diagnostic approach and the management of acoustic neuroma and to make a decision analysis tree of the diagnostic work-up. MATERIALS AND METHODS:From June 1994 through May 1998, eight patients with a small acoustic neuroma were treated at Ajou University Hospital. We analysed these 8 patients by age, sex, chief complaint, size of tumor, preoperative and postoperative audiologic studies, caloric test, treatment modalities and preoperative and postoperative imaging study. RESULTS: Acoustic neuroma had variable symptoms, with the most common initial symptom of our cases being sudden hearing loss. The sensitivity of ABR was relatively lower than we thought. Two out of three in the observation group showed an abrupt deterioration of hearing. CONCLUSION: When acoustic neuroma is suspected in patients with unilateral hearing loss, tinnitus and dizziness are very important symptoms to consider. We developed a decision analysis tree for diagnosis of small acoustic neuroma, which should be treated with earlier intervention of MRI.

Hearing Preserved Four Cases of Iatrogenic Labyrinthine Fistula Treatment / 대한이비인후과학회지

Evaluation of postoperative hearing acuity and equilibrium was performed in four patients with labyrinthine fistula caused by iatrogenic procedure. Surgical trauma inflicted upon the membranous labyrinth is an uncommon, but often catastrophic, complication of chronic ear surgery. The most vulnerable areas are the oval window and the lateral semicircular canal. Methods of injury include subluxation of the foot plate, fracture of the lateral canal by drill or chisel, and accidental opening of the labyrinth. Three cases of fistula of the lateral and posterior canal during ear surgery are presented. All of three occured while drilling. The other one occured due to iatrogenic stapedectomy. The interrupted semicircular canals were obliterated firmly with autologous materials such as fascia, perichondrium, bone chips, and cartilage. These cases were documented by pre and post operative audiograms, vestibular function tests. One interesting finding was that none of these cases were compromised cochlear function. The dictum that an accidentally opened labyrinth will automatically result in a dead ear is shown to be not necessarily true. These cases indicates that manipulation of the semicircular canal with awareness can be conducted without damaging the cochlear function, and that the treatment of labyrinthine fistulas shoud be performed very carefully but not so conservatively as to lead to future problems.

An Experience of Early Surgical Intervention for Neurofibromatosis Type II / 대한이비인후과학회지

Neurofibromatosis type II(NF2) is clinically characterized by the presence of bilateral vestibular schwannomas. The exclusive goal in management of NF2 patients is hearing preservation. It has been controversial to determine whether to wait and see or to try early surgical management for hearing preservation. The authors experienced a case of vestibular schwannoma in association with NF2, which was partially removed and decompressed via middle fossa approach with hearing preservation. Based on our experience, we recommend a new strategy for hearing preservation on early surgical intervention of vestibular schwannoma. The criterias of the patient include (1) bilateral normal or serviceable hearing: (2) small sized tumorand: (3) young age. We suggest that the early surgical intervention including decompression may be considered for the hearing preservation especially on the favorable side to approach.

Partial Posterior Canal Labyrinthectomy for Pontine Cavernous Angioma

The transpetrosal approach to the anterior portion of a brain stem lesion with intact hearing is often limited by portions of the labyrinth. The technique of partial labyrinthectomy, by which the posterior and superior semicircular canals, maximizes surgical exposure while preserving hearing. We report the case of a patient who underwent a modified partial labyrinthectomy involving resection of the posterior semicircular canal only in the area of the labyrinth. Technical modification of the partial labyrinthectomy approach simplifies tumor removal while preserving hearing.

Transpetrosal Approach with Partial Labyrinthectomy for Hearing Preservation: Technical Note and Case Report

The transpetrosal transtentorial supra- and infratentorial combined approach has been used by many skull base surgeons for the total removal of large tumors in the cerebellopontine, petroclival, and dumbbell-shaped mass of the middle and posterior cranial bases. When surgeons use the retrolabyrinthine approach for hearing preservation, adequate exposure of the presigmoid dura might be hard to achive. In order to get a wider operating field with hearing preservation, the authors used the transpetrosal approach with partial labyrinthectomy for a large dermoid cyst in the cerebellopontine angle which extened to the middle cranial base through the Meckel's cave.