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.