Clinical Assessment of Otolith Function

The otolith organs (the saccule and utricle) are located in the inner ear and sense linear acceleration, head tilt, and gravity. Recently, the vestibular evoked myogenic potential (VEMP) and the subjective visual vertical (SVV) have been described as clinical tests for otolith function. VEMPs are short latency electromyograms (EMG) evoked by high-level acoustic and vibratory stimuli recorded from surface electrodes over the tonically contracted SCM muscles (cervical VEMP) or extra-ocular muscles (ocular VEMP). The SVV is a psychophysical measure of the angle between perceptual vertical and true (gravitational) vertical and can be measured during unilateral centrifugation (off-axis eccentric rotation). The purpose of this paper is to discuss the clinical use and recent developments of the cervical VEMP, ocular VEMP, and SVV as tests of saccular and utricular function.