Faculty Bibliography

A cochlear implant (CI) is a surgically implanted device for the treatment of severe to profound sensorineural hearing loss in children and adults. It works by transducing acoustic energy into an electrical signal, which is used to stimulate surviving spiral ganglion cells of the auditory nerve. The past 2 decades have witnessed an exponential rise in the number of CI surgeries performed. Continual developments in programming strategies, device design, and minimally traumatic surgical technique have demonstrated the safety and efficacy of CI surgery. As a result, candidacy guidelines have expanded to include both pre and postlingually deaf children as young as 1 year of age, and those with greater degrees of residual hearing. A growing proportion of patients are undergoing CI for off-label or nontraditional indications including single-sided deafness, retrocochlear hearing loss, asymmetrical sensorineural hearing loss (SNHL) in adults and children with at least 1 ear that is better than performance cut-off for age, and children less than 12 months of age. Herein, we review CI design, clinical evaluation, indications, operative technique, and outcomes. We also discuss the expanding indications for CI surgery as it relates to lateral skull base pathology, comparing CI to auditory brainstem implants, and address the concerns with obtaining magnetic resonance imaging (MRI) in CI recipients.

Intralabyrinthine schwannomas (ILS) are rare tumors that frequently cause sensorineural hearing loss. The development and increased use of magnetic resonance imaging in recent years have facilitated the diagnosis of these tumors that present with otherwise nondiscriminant symptoms such as tinnitus, vertigo, and hearing loss. The following is a review of the presentation, pathophysiology, imaging, and treatment with a focused discussion on auditory rehabilitation options of ILS.

BACKGROUND:Measurement of the angular depth of insertion (aDOI) of cochlear implant electrode arrays has numerous clinical and research applications. Plain-film radiographs are easily obtained intraoperatively and have been described as a means to calculate aDOI. CT imaging with 3D reformatting can also be used for this measurement, but is less conveniently obtained and requires higher radiation doses, a particular concern in pediatrics. The extent to which plain-film and 3D CT image-based measurements are representative of the true position of the electrode within the cochlea is unknown. METHODS:Cochlear implantation was performed on 10 cadaveric temporal bones. Five bones were implanted with perimodiolar electrodes (Contour Advance TM, Cochlear, Sydney, Australia) and five were implanted with lateral wall electrodes (Slim Straight, Cochlear). The insertion depths of the electrodes were varied. Each bone was imaged with a radiograph and CT. aDOI was measured for each bone in each imaging modality by a neurotologist and a neuroradiologist. To obtain a 'gold standard' estimate of aDOI, the implanted temporal bones were embedded in an epoxy resin and methodically sectioned at 100 μm intervals; histologic images were captured at each interval. A 3D stack of the images was compounded, and a MATLAB script used to calculate aDOI of the most apical electrode. Measurements in the three modalities (radiograph, CT, and histology) were then compared. RESULTS:The average aDOI across all bones was similar for all modalities: 423° for radiographs, 425° for CT scans, and 427° for histology, indicating that neither imaging modality resulted in large systematic errors. Using the histology-measured angles as a reference, the average error for CT-based measures (regardless of whether the error was in the positive or negative direction) was 12°, and that for radiograph-based measures was 15°. This small difference (12 vs 15° error) was not statistically significant. CONCLUSION/CONCLUSIONS:Based on this cadaveric temporal bone model, both radiographs and CTs can provide reasonably accurate aDOI measurements. In this small sample, and as expected, the CT-based estimates were more accurate than the radiograph-based measurements. However, the difference was small and not statistically significant. Thus, the use of plain radiographs to calculate aDOI seems judicious whenever it is desired to prevent unnecessary radiation exposure and expense.

Introduction The aims of this study are to investigate a possible correlation between the time point at which peak hydraulic pressure and peak force on the cochlear wall appears during insertion of a cochlear implant electrode and to investigate whether a difference exists in maximum hydraulic pressure and maximum force on the cochlear wall during a fast and slow insertion, a manual and automatic insertion and an electrode insertion into a narrow or wide round window (RW) opening. Material and methods Twenty fresh frozen human temporal bones were used. Intracochlear hydraulic pressure and force on the cochlear wall were recorded during round window insertions of a straight electrode array with different insertion speeds, different insertion methods and with different widths of the opening of the RW. Results A statistical signifcant correlation between the time point at which peak hydraulic pressure and peak force on the cochlear wall appears was found (r=0.91, p<0.001). Furthermore, a slow insertion speed showed a higher hydraulic pressure and a higher force on the cochlear wall compared to a fast insertion speed (p<0.001). No statistically signifcant effect of insertion method or the width of the opening of the RW was found on hydraulic pressure and on force on the cochlear wall. Conclusions Peak hydraulic pressure and peak force on the cochlear wall during electrode insertion seems to appear at approximately the same time. Furthermore, a slow insertion speed seems to result in a higher intracochlear hydraulic pressure and a higher force on the cochlear wall

Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and deafness (CHARGE) syndrome is a disorder with multiple congenital anomalies seen on imaging. A retrospective review of 10 patients with CHARGE syndrome who underwent MR imaging of the brain as part of a preoperative evaluation for cochlear implantation was conducted. Structural abnormalities of the entire MR imaging of the head were evaluated, including the auditory system, olfactory system, face, skull base, and central nervous system. The most frequent MR imaging findings included dysplasias of the semicircular canals and hypoplasia of the frontal lobe olfactory sulci. Less frequent findings included cleft lip/palate and coloboma. Our study uncovered new findings of a J-shaped sella, dorsal angulation of the clivus, and absent/atrophic parotid glands, not previously described in patients with CHARGE. Our results emphasize the utility of MR imaging in the diagnosis and management of patients with CHARGE syndrome.

HYPOTHESIS: A novel smartphone-based software application can facilitate self-selection of frequency allocation tables (FAT) in postlingually deaf cochlear implant (CI) users. BACKGROUND: CIs use FATs to represent the tonotopic organization of a normal cochlea. Current CI fitting methods typically use a standard FAT for all patients regardless of individual differences in cochlear size and electrode location. In postlingually deaf patients, different amounts of mismatch can result between the frequency-place function they experienced when they had normal hearing and the frequency-place function that results from the standard FAT. For some CI users, an alternative FAT may enhance sound quality or speech perception. Currently, no widely available tools exist to aid real-time selection of different FATs. This study aims to develop a new smartphone tool for this purpose and to evaluate speech perception and sound quality measures in a pilot study of CI subjects using this application. METHODS: A smartphone application for a widely available mobile platform (iOS) was developed to serve as a preprocessor of auditory input to a clinical CI speech processor and enable interactive real-time selection of FATs. The application's output was validated by measuring electrodograms for various inputs. A pilot study was conducted in six CI subjects. Speech perception was evaluated using word recognition tests. RESULTS: All subjects successfully used the portable application with their clinical speech processors to experience different FATs while listening to running speech. The users were all able to select one table that they judged provided the best sound quality. All subjects chose a FAT different from the standard FAT in their everyday clinical processor. Using the smartphone application, the mean consonant-nucleus-consonant score with the default FAT selection was 28.5% (SD 16.8) and 29.5% (SD 16.4) when using a self-selected FAT. CONCLUSION: A portable smartphone application enables CI users to self-select frequency allocation tables in real time. Even though the self-selected FATs that were deemed to have better sound quality were only tested acutely (i.e., without long-term experience with them), speech perception scores were not inferior to those obtained with the clinical FATs. This software application may be a valuable tool for improving future methods of CI fitting.

Tympanic paragangliomas (TP) arise in the middle ear along the course of Jacobson's or Arnold's nerve. These lesions can vary from small masses on the cochlear promontory to tumors that extend into the mastoid and external auditory canal. Surgical excision is the treatment of choice for TP with very low-recurrence rates. The various surgical approaches for TP are adapted to the configuration of individual tumors to provide adequate exposure to the margins of the tumor in the mesotympanum, hypotympanum, and mastoid. Using these surgical approaches in combination with meticulous dissection and hemostasis with adjunctive tools such as laser and micro-bipolar instruments allows for safe and effective resection of these vascular tumors from within the confines of the tympanic cavity

OBJECTIVE: To describe the clinical outcomes of patients undergoing serial observation for vestibular schwannoma (VS) and identify factors that may predict tumor growth or hearing loss. STUDY DESIGN: Retrospective review. METHODS: A retrospective review was conducted of patients seen at a tertiary care medical center between 2002 and 2013 with an International Classification of Diseases-9 diagnosis code of 225.1. Patients electing observation as initial management, with at least two documented imaging results, were included. Exclusion criteria comprised bilateral VS, diagnosis of neurofibromatosis type 2, and neoplasms other than VS. Decline in serviceable hearing, tumor growth, and changes in management strategy were recorded. Survival analysis to assess median time to outcomes and multiple logistic regression analyses were performed. RESULTS: A total of 94 patients met inclusion criteria. While undergoing observation, 22.3% of patients underwent a change in management strategy to microsurgical excision or stereotactic radiotherapy. For patients with initial serviceable hearing, 24.3% observed a decline to a nonserviceable level. No significant clinical factors were identified to predict changes in hearing. Survival analysis revealed that an estimated 69.1% of patients electing observation as initial management continued to do so at 5 years. Imbalance or disequilibrium at presentation was found to be associated with an increased adjusted odds ratio (OR) (OR 2.96; 95% confidence interval, 1.03-8.50; P = 0.04) for tumor growth. CONCLUSION: Serial observation of VS is a viable treatment strategy for selected patients, with two-thirds of patients electing to continue this management option after 5 years. Disequilibrium as a presenting symptom may be associated with subsequent tumor growth. LEVEL OF EVIDENCE: 4. Laryngoscope, 2015.