title: Vestibular evoked myogenic potentials in brainstem stroke.
abstract: OBJECTIVE
  Despite its widespread application in the posterior fossa tumor, the study of vestibular evoked myogenic potential (VEMP) in cases of posterior fossa stroke remains scarce. The purpose of the study was to establish the role of VEMP in patients with brainstem stroke.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Patients with acute vertigo were admitted and underwent a battery of auditory vestibular tests including caloric and VEMP tests; then they were surveyed by magnetic resonance imaging scan. Seven patients (two men and five women) were demonstrated as having brainstem stroke, including infarction in five patients and hemorrhage in two.
  
  
  RESULTS
  Clinical manifestations consisted of dizziness/vertigo in all patients, spontaneous nystagmus in five (71%), and ataxia in three. No patients had experienced conscious change or conventional neurological deficits (eg, long tract signs). Electronystagmography revealed abnormal findings on eye tracking test in 100% of patients, on optokinetic nystagmus test in 71% of the patients, and on caloric testing in 10 ears (71%), including absent ice-water caloric test response in 7 ears and canal paresis in 3 ears. Vestibular evoked myogenic potential testing displayed normal response in 3 ears and abnormal response in 11 ears (79%), including absent vestibular evoked myogenic potentials in 8 ears and delayed vestibular evoked myogenic potentials in 3 ears. When results of both caloric testing and VEMP test were combined, the abnormal rate increased to 93% (13 of 14 patients).
  
  
  CONCLUSIONS
  Caloric testing assesses the vestibulo-ocular reflex, which passes upward through the upper brainstem, whereas VEMP testing evaluates the sacculocollic reflex, which travels downward through the lower brainstem. Hence, in evaluating the extension of brainstem stroke, both caloric and VEMP testing should be performed.
authors.affiliation: Department of Otolaryngology, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei.
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Chen
authors.forename: Yi-Ho
authors.initials: YH
authors.lastname: Young
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D000368:Aged; D001933:Brain Stem / Q000473:pathology / Q000503:physiopathology; D020526:Brain Stem Infarctions / Q000175:diagnosis* / Q000503:physiopathology; D002150:Caloric Tests; D002543:Cerebral Hemorrhage / Q000175:diagnosis* / Q000473:pathology; D003937:Diagnosis, Differential; D004569:Electroencephalography; D004584:Electronystagmography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000294:innervation*; D017120:Nystagmus, Optokinetic / Q000502:physiology; D011237:Predictive Value of Tests; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D014717:Vertigo / Q000175:diagnosis / Q000503:physiopathology; D014724:Vestibular Function Tests; D014725:Vestibular Nerve / Q000503:physiopathology*; D014726:Vestibular Nuclei / Q000503:physiopathology*