Diagnostic value of prolonged latencies in the vestibular evoked myogenic potential.

BACKGROUND: As a parameter for the evaluation of the vestibular evoked myogenic potential (VEMP), amplitude has been used clinically. However, the significance 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 and compared them with records of healthy volunteers.

SETTING: Data were collected from patients in an outpatient clinic of a tertiary 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, acoustic neuroma in 62 patients, vestibular neuritis in 23 patients, and multiple 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 amplitudes 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 disease or vestibular neuritis hardly showed any latency prolongation. Four patients 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 retrolabyrinthine, especially in the vestibulospinal tract.