Prediction of the nerves of origin of vestibular schwannomas with vestibular evoked myogenic potentials.

Objective: To determine whether the nerves of origin of vestibular schwannomas can be predicted using vestibular evoked myogenic potentials (VEMPs).

Study design: The study was a retrospective analysis.

Setting: The ear, nose, and throat department of Tokyo Medical and Dental University.

Patients: Twenty-eight patients undergoing removal of vestibular schwannomas were included in the study.

Interventions: Patients underwent pure tone audiometry, VEMP testing, caloric testing, and magnetic resonance imaging preoperatively. Hearing level, caloric weakness, maximum tumor size, and the nerves of origin of tumors were compared with VEMP testing.

Main outcome measure: Results of VEMP testing.

Results: Comparisons between VEMPs and results of the other three examinations revealed no correlations. Complete disappearance of VEMPs was observed only in patients with tumors arising from inferior vestibular nerves. Patients in whom hearing was preserved tended to have preserved VEMPs. Some patients showed damaged hearing and normal VEMP results, although with inferior vestibular schwannomas. A patient with a tumor arising from a cochlear nerve exhibited preservation of VEMP, preserved caloric response, and moderate hearing loss.

Conclusions: Inferior vestibular nerve function and hearing level were reflected in VEMP results. Prediction of the nerve of origin of a tumor was possible only in certain restricted cases.