Vestibular Evoked Myogenic Potentials in Patients With Acoustic Neuromas

TLDR

Acoustic neuromas are typically diagnosed with MRI, auditory brainstem response, and caloric testing, which assess cochlear and superior vestibular nerve function. The authors hypothesize that vestibular evoked myogenic potentials, reflecting inferior vestibular nerve function, could offer complementary diagnostic information for acoustic neuromas. They reviewed preoperative VEMP recordings from 21 surgically confirmed AN patients and 8 normal controls to assess inferior vestibular nerve involvement. Seventy‑eight percent of patients showed abnormal VEMPs, and discrepancies between VEMP and caloric responses in some cases indicate that VEMP can aid in diagnosing acoustic neuromas and classifying nerve involvement.

Abstract

To diagnose acoustic neuromas (ANs), the auditory brainstem response test and the caloric test have been used in addition to magnetic resonance imaging. The auditory brainstem response and the caloric tests mainly reflect functions of the auditory pathway, ie, the cochlear nerve and the superior vestibular nerve, respectively. Because the vestibular evoked myogenic potential (VEMP) has been thought to originate in the inferior vestibular nerve, we hypothesized that the VEMP could provide different information from the auditory brainstem response and the caloric test and that it could be helpful in diagnosing ANs. In other words, we hypothesized that the VEMP could provide information concerning inferior vestibular nerve involvement in patients with ANs.To find out if the VEMP could be useful in classifying ANs according to the involved nerves.We reviewed preoperative clinical tests, including VEMPs, in 21 patients (8 men, 13 women) with ANs confirmed surgically and histopathologically, comparing them with VEMPs in 8 normal subjects (5 men, 3 women).Whereas the first positive-negative peak of the VEMP, P13-N23, was ipsilaterally present on stimulation of the unaffected side in all patients with ANs and both sides in all normal subjects, it was absent on the affected side in 15 patients (71%) and significantly decreased in amplitude in 2 patients (9%). Thus, 17 (80%) of the 21 patients showed abnormal VEMPs. Three patients had abnormal VEMPs although they had normal caloric responses. Three patients had abnormal caloric responses although they had normal VEMPs.These results suggest that the VEMP could be useful for the diagnosis of AN, especially for classifying ANs according to the involved nerves.