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.