SY2.7. Evaluation of the vestibular system: cVEMP and oVEMP

Abstract

The vestibular system makes strong connections with the oculomotor nuclei, the neck, the cerebellum and also projects to the cortex. Over- or under-activity of vestibular afferents causes disturbances of posture, vision and perception. While methods have been available for some time for assessing some of the properties of the vestibular system, these have had limitations. These methods have been difficult to apply widely, either being indirect and not always well tolerated (rotating chairs, centrifuges and caloric testing) or poorly standardised, such as galvanic stimulation in standing subjects. Relatively simple methods of assessing short latency vestibular projections have become available. The best known of these require averaging of muscle activity thus are termed “vestibular evoked myogenic potentials” or VEMPs. Short latency potentials can be recorded from the sternocleidomastoid muscle in the neck (cervical VEMPs) or from the inferior oblique (ocular VEMPs). Both can be evoked by either air conducted sound (AC) or bone conducted sound (BC). The AC-evoked cVEMP mainly reflects saccular function and the oVEMP mainly utricular. Most recently it has been possible to record an evoked potential from the cerebellum (VsCEP). The VEMP techniques are well tolerated and have been widely applied in vestibular diagnosis. They have also been used in investigations of central disorders such as multiple sclerosis, Parkinson’s disease and progressive supranuclear palsy (PSP).