Acute sensorineural hearing loss in patients with vestibular schwannoma early after cyberknife radiosurgery

Objective: This study reviewed our experience in treating patients with vestibular schwannoma (VS) who had acute sensorineural hearing loss (ASHL) early after radiosurgery. Patients and methods: Seventy VS patients underwent cyberknife radiosurgery. Of them, 6 patients had ASHL early (< 6 m) after radiosurgery (Group A), accounting for 8.6% prevalence. The remaining 64 patients without ASHL were assigned to Group B. Another 10 VS patients with tiny tumor and serviceable hearing adopted observation policy (Group C). All patients underwent a test battery for inner ear function, and tumor size was measured via MR imaging. Results: The mean hearing level of Group A was 39 +/- 16 dB before radiosurgery, which deteriorated to 67 +/- 14 dB at the onset of ASHL after radiosurgery. Three months after treatment for ASHL, hearing improvement was noted in only one patient (17%). Mean tumor volumes of Group A before and after ASHL were 1.54 +/- 1.48 cc and 1.33 +/- 1.04 cc, respectively, showing non-significant difference. Receiver operating characteristic curve analysis revealed that the optimal cutoff value for tumor size was 1.45 cm for predicting absence of ASHL, with a sensitivity of 96% and a specificity of 67%. In contrast, Group C with mean tumor size of 0.64 +/- 0.15 cm adopted observation policy, and none of them had ASHL two years after diagnosis. Conclusion: Prevalence of ASHL in VS patients early after radiosurgery is 8.6%, likely due to radiation injury to the cochlear nerve. Thus, when tumor size is < 1.45 cm, serviceable hearing is the criteria for determining whether observation policy (with serviceable hearing) or radiosurgery (lack of serviceable hearing) is given. For those tumor sizes ranged 1.45-3.0 cm, radiosurgery is indicated regardless of hearing level.