Cochlear Implantation after Radiosurgery for Vestibular Schwannoma

Objective: The optimal strategy for hearing rehabilitation in neurofibromatosis type 2 (NF2) and sporadic vestibular schwannoma (VS) remains undefined. Unfortunately, audiologic outcomes of auditory brainstem implantation are generally limited. In contrast, cochlear implantation (CI) typically yields open-set speech understanding and access to sound by pure tone audiometry in the near-normal range, both of which exhibit durability over time. This has led many to adopt treatment strategies for patients with bilateral sensorineural hearing loss (SNHL) and unilateral or bilateral VS that emphasize preservation of an anatomic cochlear nerve. At our institution, radiosurgical treatment of VS with subsequent ipsilateral cochlear implantation has been utilized for a series of patients with sporadic and NF2-related VS. In this report, audiologic outcomes of CI following radiosurgery are presented.

Setting: Tertiary academic referral center.

Methods:: A retrospective review of adult patients with VS treated with stereotactic radiosurgery (SRS), followed by cochlear implantation, between 1990 and 2019 was performed. Patient demographics, tumor features, treatment parameters, and pre- and postimplantation audiometric outcomes (including pure tone average [PTA] and word and sentence test scores) are presented.

Results: Sixteen patients (17 ears) underwent SRS and ipsilateral CI during the study period. Thirteen patients (81%) had NF2. Median age at SRS and CI were 44 and 48 years, respectively. Median time from SRS to CI was 38 days, but notably, five patients underwent SRS and CI within 1 day and four patients underwent CI greater than 7 years following SRS. Median tumor volume at the time of SRS was 1,400 mm³ (range = 83.6–6080 cubic mm, n = 15). Fifteen patients underwent primary Gamma Knife SRS at our institution with a median marginal dose of 13 Gy delivered to the 50% isodose line. Median post-CI PTA was 29 dB HL, improved from 110 dB HL preoperatively (p = 0.004). Overall, 11 patients exhibit speech understanding without visual cues. All underwent sentence testing at a median 7 months (range = 1–143 months) post-CI. The median AzBio sentence score was 85% (range = 46–95%, n = 8). Two ears exhibited HINT sentence scores of 49 and 95%, respectively. The remaining five patients achieved environmental sound awareness without open-set speech recognition.

Conclusion: Patients who undergo CI following SRS for VS enjoy access to sound at near normal levels, with the majority achieving open-set speech understanding. Implantation can be performed immediately following SRS or in a delayed fashion, depending upon hearing status among other factors. This strategy may be applied to cases of sporadic or NF2-associated VS.

Fig. 1 Axial T1 postcontrast MRI with artifact suppression and cochlear implant only audiometry for a patient with neurofibromatosis type 2 who underwent bilateral sequential cochlear implantation after L sided SRS and R sided surgery and SRS. The patient enjoys open-set speech understanding with both implants. MRI, magnetic resonance imaging; SRS, stereotactic radiosurgery.