Driscoll, Colin L. W.

OBJECTIVE The object of this study was to ascertain outcomes of cochlear implantation (CI) following stereotactic radiosurgery (SRS) for vestibular schwannoma (VS). METHODS The authors conducted a retrospective chart review of adult patients with VS treated with SRS who underwent CI between 1990 and 2019 at a single tertiary care referral center. Patient demographics, tumor features, treatment parameters, and pre- and postimplantation audiometric and clinical outcomes are presented. RESULTS Seventeen patients (18 ears) underwent SRS and ipsilateral CI during the study period. Thirteen patients (76%) had neurofibromatosis type 2 (NF2). Median age at SRS and CI were 44 and 48 years, respectively. Median time from SRS to CI was 60 days, but notably, 4 patients underwent SRS and CI within 1 day and 5 patients underwent CI more than 7 years after SRS. Median marginal dose was 13 Gy. Median treatment volume at the time of SRS was 1400 mm 3 (range 84–6080 mm 3 , n = 15 patients). Median post-CI PTA was 28 dB HL, improved from 101 dB HL preoperatively (p < 0.001). Overall, 11 patients (12 ears) exhibited open-set speech understanding. Sentence testing was performed at a median of 10 months (range 1–143 months) post-CI. The median AzBio sentence score for patients with open-set speech understanding was 76% (range 19%–95%, n = 10 ears). Two ears exhibited Hearing in Noise Test (HINT) sentence scores of 49% and 95%, respectively. Four patients achieved environmental sound awareness without open-set speech recognition. Two had no detectable auditory percepts. CONCLUSIONS Most patients who underwent CI following SRS for VS enjoyed access to sound at near-normal levels, with the majority achieving good open-set speech understanding. Implantation can be performed immediately following SRS or in a delayed fashion, depending on hearing status as well as other factors. This strategy may be applied to cases of sporadic or NF2-associated VS.

Objective: Definitive treatment of sporadic vestibular schwannoma (VS) following documented growth is common practice at most centers in the United States. However, as a natural extension of this paradigm, very little evidence exists surrounding the natural history of growing tumors. The primary objective of the current work was to describe the natural history of sporadic VS following documentation of initial tumor growth. Study Design: Retrospective cohort study. Setting: Tertiary referral center. Patients: Patients diagnosed with sporadic VS between January 1, 2001 and December 31, 2015 who elected continued observation despite having volumetric growth ≥20% of original tumor volume on interval magnetic resonance imaging (MRI). Main Outcome Measure: Survival free of subsequent volumetric growth. Results: Of 361 patients undergoing observation with serial imaging during the study period, 85 patients met inclusion criteria at a median age of 66 years (interquartile ranges [IQR] 55–71). Within this cohort, 40 patients demonstrated subsequent volumetric growth at a median of 1.7 years (IQR 1.0–2.6) from the date of initial MRI that documented growth. The median volumetric growth was 43% (IQR 28–57), and the median growth rate was 0.026 cm3 per year (IQR 0.009–0.107). Survival free of subsequent volumetric growth rates (95% CI; number still at risk) at 1, 2, 3, 4, and 5 years were 93% (87–99; 75), 67% (58–79; 45), 54% (43–67; 29), 44% (33–59; 19), and 41% (30–56; 12), respectively. Conclusions: In a cohort exclusively comprised of sporadic VS with documented growth, over 40% of tumors demonstrated no subsequent volumetric growth after 5 years of continued MRI surveillance. These data challenge the supposition that once growth occurs, all tumors will exhibit sustained growth. Continued observation after documented growth of sporadic VS is a reasonable consideration in appropriately selected cases.