Faculty Bibliography

BACKGROUND:Hearing preservation is a goal for many patients with vestibular schwannoma. We examined pretreatment magnetic resonance imaging (MRI) and posttreatment hearing outcome after stereotactic radiosurgery. METHODS:From 2004 to 2014, a cohort of 125 consecutive patients with vestibular schwannoma (VS) treated via stereotactic radiosurgery (SRS) were retrospectively reviewed. MRIs containing three-dimensional constructive interference in steady state or equivalent within 1 year before treatment were classified by two radiologists for pretreatment characteristics. "Good" hearing was defined as American Academy of Otolaryngology-Head and Neck Surgery class A. Poor hearing outcome was defined as loss of good pretreatment hearing after stereotactic radiosurgery. RESULTS:Sixty-one patients met criteria for inclusion. Most had tumors in the distal internal auditory canal (55%), separated from the brainstem (63%), oval shape (64%) without cysts (86%), and median volume of 0.85 ± 0.55 cm. Pretreatment audiograms were performed a median of 108 ± 173 days before stereotactic radiosurgery; 38% had good pretreatment hearing. Smaller tumor volume (p < 0.005) was the only variable associated with good pretreatment hearing. 49 (80%) patients had posttreatment audiometry, with median follow-up of 197 ± 247 days. Asymmetrically decreased pretreatment cochlear CISS signal on the side of the VS was the only variable associated with poor hearing outcome (p = 0.001). Inter-rater agreement on cochlear three-dimensional constructive interference in steady state preservation was 91%. CONCLUSIONS:Decreased cochlear CISS signal may indicate a tumor's association with the cochlear neurovascular bundle, influencing endolymph protein concentration and creating an inability to preserve hearing. This important MRI characteristic can influence planning, counseling, and patient selection for vestibular schwannoma treatment.

OBJECTIVE:To assess bimodal auditory performance in children with a cochlear implant (CI) and contralateral auditory brainstem implant (ABI). METHODS:This is a retrospective case review performed at a tertiary referral center. Four patients with cochlear nerve deficiency initially underwent cochlear implantation but were not benefiting from their devices and underwent ABI in the contralateral ear. The main outcome measures included age-appropriate speech perception and production assessments. RESULTS:Three subjects performed better on their auditory perception assessments using both of their devices than with either device alone. One subject had only preliminary outcomes, but subjectively performed best with both devices. CONCLUSIONS:We observed continued improvement in CI performance over time, even if no benefit was evident before the decision for ABI. This could suggest that ABI and CI have a synergistic effect, or it could simply be the adaptive ability of the developing brain to utilize the signals coming from these devices. There is preliminary evidence to support choosing the ear contralateral to the CI for an ABI in a pediatric patient with bilateral cochlear nerve deficiency.

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.

OBJECTIVE: To evaluate the safety, efficiency, cost effectiveness, and satisfaction of patients undergoing cochlear implantation under conscious sedation versus general anesthesia. STUDY DESIGN: Retrospective case review of 20 patients who underwent cochlear implantation under conscious sedation which was compared to 20 age-matched patients where surgery was performed under general anesthesia. METHODS: Perioperative times, length of stay, anesthesia drug costs, postoperative complications, and patient satisfaction were compared between the two groups. RESULTS: Conscious sedation was associated with decreased drug costs, surgery time, and anesthesia time. Length of stay was significantly longer for patients undergoing general anesthesia. Patient satisfaction was superior with conscious sedation. Perioperative morbidity was not significantly different between the two groups. CONCLUSION: Conscious sedation for cochlear implantation is a safe, efficient, and cost-effective alternative to general anesthesia. The efficacy of conscious sedation for cochlear implant surgery may expand the treatment of profound hearing loss to the elderly who are deemed too sick for general anesthesia or are fearful of the cognitive or medical consequences of general anesthesia.

OBJECTIVE: To compare the intraoperative electrically evoked auditory brainstem response (EABR) morphologies between neurofibromatosis II (NF2) adult auditory brainstem implant (ABI) recipients who had auditory percepts post-operatively and those who did not and between NF2 adult ABI recipients and non-NF2 pediatric ABI recipients. METHODS: This was a retrospective case series at a single tertiary academic referral center examining all ABI recipients from 1994 to 2016, which included 34 NF2 adults and 11 non-NF2 children. The morphologies of intraoperative EABRs were evaluated for the number of waveforms showing a response, the number of positive peaks in those responses, and the latencies of each of these peaks. RESULTS: 27/34 adult NF2 patients and 9/10 children had EABR waveforms. 20/27 (74.0%) of the adult patients and all of the children had ABI devices that stimulated post-operatively. When comparing the waveforms between adults who stimulated and those who did not stimulate, the proportion of total number of intraoperative EABR peaks to total possible peaks was significantly higher for the adults who stimulated than for those who did not (p < 0.05). Children had a significantly higher proportion of total number of peaks to total possible peaks when compared to adults who stimulated (p < 0.02). Additionally, there were more likely to be EABR responses at the initial stimulation than intraoperatively in the pediatric ABI population (p = 0.065). CONCLUSIONS: The value of intraoperative EABR tracing may lie in its ability to predict post-operative auditory percepts based on the placement of the array providing the highest number of total peaks.

OBJECTIVE: To characterize the performance plateau after unilateral cochlear implantation (CI) in prelingually and postlingually deafened adults and to compare their relative progress. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: Prelingually and postlingually deaf adults who received a unilateral CI and completed a minimum of 2 years of follow-up at our center. INTERVENTION: Unilateral CI. MAIN OUTCOME MEASURES:: Standard speech perception testing (consonant-nucleus-consonant [CNC] monosyllabic word test and hearing in noise test [HINT] or AzBio sentence test) were performed preoperatively and 3 and 12 months postoperatively, and annually thereafter. RESULTS: In postlingually deaf patients (n = 102), there was a significant improvement in word scores for 3 years postimplantation (p < 0.01). Beyond the 3 years postoperative time point, word scores continued to improve, albeit at a flatter rate. In prelingually deaf patients (n = 16) word scores improved significantly for 5 years postimplantation (p = 0.03). CONCLUSIONS: Adults with postlingual deafness undergoing unilateral CI show significant improvement in speech perception for 3 years postimplantation, at which point their performance continues to improve, albeit at a flatter rate. The performance of adults with prelingual deafness improves significantly as late as 5 years postimplantation. These time intervals reflect a change to the currently reported 6 to 12 months period and should impact on counseling, especially in the prelingual CI candidate.

OBJECTIVE: To describe our initial operative experience and hearing preservation results with the Advanced Bionics (AB) Mid Scala Electrode (MSE). STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: Sixty-three MSE implants in pediatric and adult patients were compared with age- and sex-matched 1j electrode implants from the same manufacturer. All patients were severe to profoundly deaf. INTERVENTION: Cochlear implantation with either the AB 1j electrode or the AB MSE. MAIN OUTCOME MEASURES: The MSE and 1j electrodes were compared in their angular depth of insertion and pre to postoperative change in hearing thresholds. Hearing preservation was analyzed as a function of angular depth of insertion. Secondary outcome measures included operative time, incidence of abnormal intraoperative impedance and telemetry values, and incidence of postsurgical complications. RESULTS: Depth of insertion was similar for both electrodes, but was more consistent for the MSE array and more variable for the 1j array. Patients with MSE electrodes had better hearing preservation. Thresholds shifts at four audiometric frequencies ranging from 250 to 2000 Hz were 10, 7, 2, and 6 dB smaller for the MSE electrode than for the 1j (p < 0.05). Hearing preservation at low frequencies was worse with deeper insertion, regardless of array. Secondary outcome measures were similar for both electrodes. CONCLUSION: The MSE electrode resulted in more consistent insertion depth and somewhat better hearing preservation than the 1j electrode. Differences in other surgical outcome measures were small or unlikely to have a meaningful effect.

Cochlear implants are neuroprosthetic devices that provide hearing to deaf patients, although outcomes are highly variable even with prolonged training and use. The central auditory system must process cochlear implant signals, but it is unclear how neural circuits adapt - or fail to adapt - to such inputs. Understanding these mechanisms is required for development of next-generation neuroprosthetics that interface with existing neural circuits and enable synaptic plasticity to improve perceptual outcomes. Here we describe a new system for cochlear implant insertion, stimulation, and behavioral training in rats. Animals were first ensured to have significant hearing loss via physiological and behavioral criteria. We developed a surgical approach for multi-channel (2-channel or 8-channel) array insertion, comparable to implantation procedures and depth in humans. Peripheral and cortical responses to stimulation were used to objectively program the implant. Animals fitted with implants learned to use them for an auditory-dependent task that assesses frequency detection and recognition, in a background of environmentally- and self-generated noise, and ceased responding appropriately to sounds when the implant was temporarily inactivated. This physiologically-calibrated and behaviorally-validated system provides a powerful opportunity to study the neural basis of neuroprosthetic device use and plasticity.

INTRODUCTION: Although rare, complications in cochlear implantation may result from surgical or technical mishaps, reaction to the foreign body, infection, or mechanical device failure. Delayed cerebrospinal fluid (CSF) leak is a rarely reported condition that may present with asymptomatic swelling over the receiver-stimulator (RS). In our practice, meticulous drilling of a bony well is important in preventing device migration and maintaining a low device profile but there is the potential for immediate or delayed complication from this technique. OBJECTIVE: We report two cases of the diagnosis and management of delayed extradural CSF collection of the RS bony well and describe its successful management. PATIENTS: Two pediatric cochlear implant patients, 10 and 17 months of age with devices from different manufacturers. INTERVENTION(S): Operative exploration and repair without device removal. MAIN OUTCOME AND RESULTS: Although the initial postoperative course was uncomplicated with both patients receiving benefit from their device, both presented at varying intervals month(s) later with swelling over the RS. There were no signs of infection but the swelling prevented use of the device. Extradural CSF collection was suspected, confirmed operatively, and repaired with complete resolution without the need for reimplantation. CONCLUSION: Delayed CSF leak may present as an asymptomatic swelling over the RS after cochlear implantation. Sterile fluid aspiration may confirm the diagnosis and management can proceed conservatively or with operative exploration and repair. Future device designs with lower profiles may facilitate device fixation while allowing for a more shallow well, further reducing the risk of this rare complication.