Vestibular evoked myogenic potentials in brainstem stroke
Abstract
Objectives/Hypothesis: Despite its widespread application in the posterior fossa tumor, the study of VEMP in cases of posterior fossa stroke remains scarce. The purpose of this paper is to establish the role of VEMP in patients with brainstem stroke.
Methods: Acute vertigo patients were admitted and underwent a battery of audio-vestibular testings including caloric test and VEMP test, then were surveyed by MRI scan. Seven patients (two men and five women) were demonstrated as brainstem stroke, including infarction in 5 and hemorrhage in 2.
Results: Clinical manifestations consisted of dizziness/vertigo for all patients, spontaneous nystagmus in five (71 %), and ataxia in three. None had experienced conscious change or conventional neurological deficits e.g. long tract signs. Electronystagmography revealed abnormal eye tracking test in 100%, abnormal optokinetic nystagmus test in 71 %, and abnormal caloric response in 10 ears (71 %), including absent ice-water caloric response in 7 ears, and canal paresis in 3 ears. VEMP test displayed normal response in 3 ears, and abnormal response in 11 ears (79 %), including absent VEMPs in 8 ears and delayed VEMPs in 3 ears. If both caloric test and VEMP test are combined, abnormal rate raises up to 93 % (13/14).
Conclusions: Caloric test assesses the vestibulo-ocular reflex, which passes ascend through the upper brainstem; whereas VEMP test evaluates the sacculo-collic reflex, which travels descend via the lower brainstem. Hence, in evaluating the extension of brainstem stroke, both caloric test and VEMP test should be performed.
