Vestibular nerve compression: role of auditory brainstem response and cervical vestibular evoked myogenic potentials

Abstract

The objective of the study was to evaluate the role of ABR and cVEMP in the diagnosis of vestibular compression syndrome (VCS) and to study the association of test results with the MRI findings. This is a case-report of four patients with VCS using case-study approach. Four patients with varying degrees of indentation of vestibulo-cochlear nerve by the anterior inferior cerebellar artery (AICA) loops were studied. Episodic rotatory vertigo was reported by three cases and two cases complained of tinnitus but the characteristic low-frequency ‘type-writer’ type of tinnitus was seen in only one. All cases showed evidence of retrocochlear pathology on ABR although two had normal peripheral hearing status. The cVEMP abnormalities noted were absence of cVEMP and reduced amplitude of cVEMP as compared to instrument-specific age-matched norms; only one case with no indentation of vestibulo-cochlear nerve had normal cVEMP tracings. Presence of AICA loops on the MRI by itself need not necessarily indicate vestibular compression syndrome. However when MRI excludes any other pathology in cases with symptoms such as unilateral sensorineural hearing loss, tinnitus, vertigo; vestibular compression could be the etiology. The likelihood of abnormal test findings is greater when the loop causes indentation of the nerve.