The classification used to predict hearing preservation in patients with unilateral vestibular schwannoma treated with stereotactic radiosurgery: Reinterpretation of the auditory brainstem response

Keywords: vestibular schwannoma, hearing preservation, gamma knife, brainstem auditory evoked potential, grading system

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     Hearing outcomes are important after vestibular schwannoma radiosurgery.
We performed this study to identify the prognostic factors for hearing preservation, which would allow the more accurate stratification of patients treated with stereotactic radiosurgery (SRS) for unilateral sporadic vestibular schwannomas (VS).
     A total of 119 patients with VS and serviceable hearing were treated with SRS as a primary treatment. The mean age of the patients was 48±11 years, and the mean follow-up duration was 55.2±35.7 months.
     The median marginal dose was 12.0 Gy. The mean tumor volume was 1.95±2.24 cm3. The mean score of pure tone average (PTA) was 26±12 (range, 4–50). The mean maximum speech discrimination score was 91%±12% (range, 52–100). The mean baseline values of interlatency of wave I and III (IL I-III) and IL I-V on auditory brainstem response (ABR) were 2.58±0.60 mS (range, 1.92–4.30) and 4.80±0.61 mS (range, 3.80–6.40), respectively.
     In the multivariate analysis, only the PTA score and IL I-V were significant and independent prognostic factors (HR=1.072; 95% CI, 1.046–1.098; p<0.001; HR=1.534; 95% CI, 1.008–2.336; p=0.046, respectively). Using the PTA score and IL I-V, we were able to classify the patients into four groups. The ratios of patients with serviceable hearing at the last clinical follow-up were 89.6%, 64.0%, 25.8%, and 6.7%, in order from group A to D (p<0.001).
     This was a retrospective study.
     The classification system based on use of the PTA score and IL I-V of the ABR may be useful and specific in predicting the rate of hearing preservation in each individual. And this classification system will guide an individualized treatment strategy for hearing preservation in patients with VS.
     New concepts are necessary to study hearing preservation outcomes.


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