Objective verification of full recovery of dynamic vestibular function after superior vestibular neuritis.

INTRODUCTION The following reports the value of new objective measures of the dynamic function of the semicircular canals and otoliths of a patient during acute unilateral superior vestibular neuritis (SVN), compared to the same objective measures 3 months later. This comparison showed that there was full recovery from the SVN. This report shows that it is possible to obtain fast, simple, accurate, objective evidence of the status of the major vestibular sense organs using published clinical tests that are firmly based on anatomical and physiological evidence. These tests can be carried out even in patients in the midst of a major vertigo attack without causing the patient distress, in contrast to a caloric test. The test results allow the clinician to distinguish between a vertigo attack due to vestibular neuritis as opposed to an attack due to Ménière’s disease (MD), because the published evidence shows that the test results of patients in these two conditions have very different response profiles as we explain below. To our knowledge this is the first case of objectively verified recovery of dynamic utricular function reported in the literature. If a patient is seen during the acute stage of a vestibular disease, a clinician can identify the classical signs and symptoms, which are dependent on the absent function of the affected vestibular sense organ. Such classical static clinical signs are: 1) spontaneous nystagmus with the quick phase of the horizontal component directed away from the affected ear, indicating reduced static horizontal semicircular canal function of the affected ear; 2) ocular torsion with both eyes rolled toward the affected ear, indicating unilaterally reduced otolithic function of the affected ear; 3) skew deviation with a vertical misalignment between the two eyes such that the ipsilesional eye shows a lower position in the orbit; and 4) postural instability with sensations of falling toward the lesioned side, related to reduced function of the affected ear projecting to ipsilateral vestibulo-spinal responses. The usual standard tests of dynamic vestibular function are: 1) the canal paresis measure from Fitzgerald-Hallpike caloric testing; and 2) the head impulse sign—during brief, passive, unpredictable, horizontal head turns toward the affected ear. The patient with reduced unilateral horizontal canal function fails to maintain fixation on an earth-fixed target, and so makes corrective (overt) saccades at the end of the head rotation to regain fixation. During similar rotations toward the healthy ear no overt saccades are evident. The overt saccade is a sign of reduced dynamic horizontal canal function; however, this sign is subjective in that there is no objective measure of the head velocity stimulus or the eye velocity response and therefore no objective measure of vestibulo-ocular reflex (VOR) gain. More recently, vestibular-evoked myogenic potentials have become widely used. The cervical vestibularevoked myogenic potential (cVEMP) to air-conducted sound (ACS) or bone-conducted vibration (BCV), stimuli that have been shown to activate otolithic neurons, indicate dynamic human saccular and inferior vestibular nerve function. In response to BCV or intense ACS stimulation, healthy subjects with surface electrodes From the MSA ENT Academy Center (L.M.), Cassino, Italy; and the Vestibular Research Laboratory (A.M.B., H.G.M., I.S.C.), School of Psychology, The University of Sydney, Sydney, New South Wales, Australia.