Vestibular evoked myogenic potentials in practice: Methods, pitfalls and clinical applications.

Vestibular evoked myogenic potentials (VEMPs) are a useful and increasingly popular component of the neuro-otology test battery. These otolith-dependent reflexes are produced by stimulating the ears with air-conducted sound or skull vibration and recorded from surface electrodes placed over the neck (cervical VEMPs) and eye muscles (ocular VEMPs). VEMP abnormalities have been reported in various diseases of the ear and vestibular system, and VEMPs have a clear role in the diagnosis of superior semicircular canal dehiscence. However there is significant variability in the methods used to stimulate the otoliths and record the reflexes. This review discusses VEMP methodology and provides a detailed theoretical background for the techniques that are typically used. The review also outlines the common pitfalls in VEMP recording and the clinical applications of VEMPs.

Ocular vestibular evoked myogenic potentials produced by impulsive lateral acceleration in unilateral vestibular dysfunction.

OBJECTIVE: To deduce the connectivity underlying ocular vestibular evoked myogenic potentials (OVEMPs) recorded from two sites and produced by lateral transmastoid stimulation in patients with unilateral vestibular dysfunction. METHODS: OVEMPs were recorded using lateral impulsive stimuli delivered by a hand-held minishaker placed at the mastoid. Twelve patients were tested using the typical OVEMP recording montage placed inferior to the eyes. In a subset of 6 patients, recordings were also made using a lateral electrode montage. The majority of patients were tested following surgery for inner ear disease. Patient responses were compared to those in normal subjects under similar recording conditions. RESULTS: For the inferior montage, regardless of which mastoid was stimulated, deficits were observed only from the eye opposite the affected ear. In contrast, OVEMPs recorded using the lateral electrode montage showed changes on both sides. CONCLUSIONS: OVEMPs produced using lateral transmastoid stimulation and recorded from beneath the eyes are generated by a crossed vestibulo-ocular pathway while the projections underlying the lateral responses are likely to be bilateral. SIGNIFICANCE: The vestibular-ocular connectivity underlying the OVEMPs recorded from inferior and lateral recording sites differs. For clinical use, the inferior recording site is the simplest to interpret.