Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential

Background: As a parameter for the evaluation of the vestibular evoked myog enic potential (VEMP), amplitude has been used clinically. However, the sig nificance of latency has not been considered. Objective: To clarify the diagnostic value of latencies of the VEMP. Design: We reviewed records of the VEMP of patients with various diseases a nd compared them with records of healthy volunteers. Setting: Data were collected from patients in an outpatient clinic of a ter tiary care center and healthy volunteers. Subjects: Clinical records of 134 patients (61 men and 73 women, aged 20-75 years) were reviewed. Diagnoses were Meniere disease in 43 patients, acous tic neuroma in 62 patients, vestibular neuritis in 23 patients, and multipl e sclerosis in 6 patients. Also, 18 healthy volunteers (13 men and 5 women, aged 25-38 years) were enrolled. Intervention: Diagnostic. Main Outcome Measures: Click-evoked myogenic potentials were recorded with surface electrodes over each sternocleidomastoid muscle. Latencies and ampl itudes of responses were measured. Results: Vestibular evoked myogenic potentials were absent or decreased in 51% of patients with Meniere disease (n=22), 39% with vestibular neuritis ( n=9), 77% with acoustic neuroma (n=48), and 25% with multiple sclerosis (3 of 12 sides of 6 patients). Concerning latency, patients with Meniere disea se or vestibular neuritis hardly showed any latency prolongation. Four pati ents with acoustic neuroma showed prolonged p13; all had large tumors. All patients with multiple sclerosis showed prolonged p13. Conclusion: Prolonged latencies of the VEMP suggest lesions in the retrolab yrinthine, especially in the vestibulospinal tract.