Electrocochleography During Translabyrinthine Approach for Vestibular Schwannoma Removal

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment

OBJECTIVE

To review the literature on the diagnosis and treatment of vestibular schwannoma.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy.

CONCLUSIONS

Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Intraoperative Cochlear Nerve Monitoring in Vestibular Schwannoma Microsurgery

Monitoring the cochlear nerve during vestibular schwannoma (VS) microsurgery depends on the hearing status and surgical approach. Traditional hearing preservation VS microsurgery relies on acoustically driven auditory brainstem response (ABR) and cochlear nerve action potential. Both modalities have advantages and disadvantages that need to be understood for proper implementation. When hearing is lost or the approach violates the otic capsule, electrically evoked monitoring methods may be used. Evoked ABR (eABR) is feasible and safe but may be limited by artifact. Combining eABR with near-field measures such as electrocochleography or neural telemetry shows promise.

Endoscopic retrosigmoid keyhole approach in cerebellopontine angle tumors. A surgical cohort

INTRODUCTION AND OBJECTIVES

To determine the safety and efficacy of endoscopic keyhole surgery in patients with cerebellopontine angle tumours.

MATERIALS AND METHODS

This was a retrospective study of patients with cerebellopontine angled tumours treated by fully endoscopic retrosigmoid keyhole approach in a tertiary centre during a period of four years. Preoperative, transoperative and postoperative variables were analysed.

RESULTS

A number of 40 patients were included. The age average was 49.4 years and male/female proportion was 0.4-1. We found 31 vestibular schwannomas (77.5%), five meningiomas (12.5%), two cholesteatomas (5.0%) and two metastases (5.0%). Vestibular schwannomas Hannover type IIIb, IVa and IVb predominated. The surgical resection was total or near-total 92.5% of patients. Hearing preservation rate was 62.5% and acceptable facial function nerve function rate was 80% after six months. Hospital stay was 7.5 days. The total or near total resection and functionally preservation rate was high. Complications were unusual.

CONCLUSIONS

Endoscopic retrosigmoid keyhole approach represented a safe and efficient procedure in selected patients with cerebellopontine angle tumours.

Intraoperative Electrocochleography in Subjects Affected by Vestibular Schwannoma and Ménière's Disease: Comparison of Results

OBJECTIVES

Histologic reports of temporal bones of ears with vestibular schwannomas (VSs) have indicated findings of endolymphatic hydrops (ELH) in some cases. The main goal of this investigation was to test ears with VSs to determine if they exhibit electrophysiological characteristics similar to those of ears expected to experience ELH.

DESIGN

Fifty-three subjects with surgically confirmed VS aged ≥18 and with normal middle ear status were included in this study. In addition, a second group of adult subjects (n = 24) undergoing labyrinthectomy (n = 6) or endolymphatic sac decompression and shunt (ELS) placement (n = 18) for poorly controlled vestibular symptoms associated with Meniere's disease (MD) participated in this research. Intraoperative electrocochleography (ECochG) from the round window was performed using tone burst stimuli. Audiometric testing and word recognition scores (WRS) were performed preoperatively. ECochG amplitudes, cochlear microphonic/auditory nerve neurophonic (ANN) in the form of the "ongoing" response and summation potential, were analyzed and compared between the two groups of subjects. In addition, to evaluate any effect of auditory nerve function, the auditory nerve score was calculated for each subject. Pure-tone averages were obtained using the average air conduction thresholds at 0.5, 1, and 2 kHz while WRS was assessed using Northwestern University Auditory Test No. 6 word lists.

RESULTS

In the VS group the average pure-tone averages and WRS were 59.6 dB HL and 44.8%, respectively, while in the MD group they were 52.3 dB HL and 73.8%. ECochG findings in both groups revealed a reduced trend in amplitude of the ongoing response with increased stimulus frequency. The summation potential amplitudes of subjects with VS were found to be less negative than the MD subjects for nearly all test frequencies. Finally, the VS group exhibited poorer amounts of auditory nerve function compared to the MD group.

CONCLUSIONS

The current findings suggest cochlear pathology (e.g., hair cell loss) in both groups but do not support the hypothesis that VSs cause ELH.

Challenges of Cochlear Implantation in Intralabyrinthine Schwannoma Patients: Surgical Procedures and Auditory Outcome

Intralabyrinthine schwannoma (ILS) is a rare benign tumor of the inner ear potentially causing unilateral sensorineural hearing loss and vertigo. This study evaluated the outcome of one surgical session comprising microsurgical ILS resection and cochlear implantation in terms of surgical feasibility, complications, and auditory outcome. Ten clinically and histologically confirmed ILS patients included in this study (three women and seven men; mean age 56.4 ± 8.6) underwent surgery between July 2015 and February 2020. Eight patients had intracochlear tumor location; the remaining two had vestibulocochlear and intravestibular ILS. One of the three following methods was used for tumor removal: an extended cochleostomy, subtotal cochleoectomy, or a translabyrinthine approach. Although negligible improvement was observed in two of the patients, two patients were lost to follow-up, and one opted out from using CI, the speech perception of the five remaining ILS patients improved as per the Freiburg Monosyllable Test (FMT) from 0% before surgery to 45– 50% after the implantation. Our study supports the presented surgical approach’s feasibility and safety, enabling tumor removal and hearing restoration shortly after surgery.

Endoscopic retrosigmoid keyhole approach in cerebellopontine angle tumors. A surgical cohort

INTRODUCTION AND OBJECTIVES

To determine the safety and efficacy of endoscopic keyhole surgery in patients with cerebellopontine angle tumors.

MATERIALS AND METHODS

This was a retrospective study of patients with cerebellopontine angled tumors treated by fully endoscopic retrosigmoid keyhole approach in a tertiary center during a period of four years. Preoperative, transoperative and postoperative variables were analyzed.

RESULTS

A number of 40 patients were included. The age average was 49.4 years and male/female proportion was 0.4-1. We found 31 vestibular schwannomas (77.5%), five meningiomas (12,5%), two cholesteatomas (5,0%) and two metastases (5.0%). Vestibular schwannomas Hannover type IIIb, IVa and IVb predominated. The surgical resection was total or near-total 92.5% of patients. Hearing preservation rate was 62.5% and acceptable facial function nerve function rate was 80% after six months. Hospital stay was 7.5 days. The total or near total resection and functionally preservation rate was high. Complications were unusual.

CONCLUSIONS

Endoscopic retrosigmoid keyhole approach represented a safe and efficient procedure in selected patients with cerebellopontine angle tumors.