The role of rotational stimulation in vestibular compensation.

1 Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. R ecently, clinical vestibular tests have been developed for assessing otolith function. Little is known about treatment for otolith dysfunction, and this case report offers a perspective on using otolith stimulation to treat vestibular loss. A 62-year-old man underwent a left vestibular neurectomy for Ménière's disease and presented to the Mountain Home Veterans Affairs (VA) Medical Center Vestibular/Balance Clinic 5 years later with complaints of imbalance and a ''float-ing sensation.'' Pure-tone audiometry revealed a mild right sensorineural hearing loss and a moderately severe left sensori-neural hearing loss. Videonystagmography revealed normal ocular motor function, mild right beating spontaneous nystag-mus, and 100% left unilateral weakness and 68% right directional preponderance on the bithermal binaural caloric test. The rotary chair test revealed normal vestibulo-ocular reflex (VOR) gain, borderline-normal low-frequency phase lead, and a left asymmetry. These findings are consistent with an uncompensated peripheral vestibular (horizontal semicircular canal and/or superior vestibular nerve) hypofunction on the left side. Vestibular-evoked myogenic potentials (VEMPs) and subjective visual vertical (SVV) testing were performed as a measure of otolith function. Cervical VEMPs to air-conducted 500-Hz tone bursts (120 peak sound pressure level [SPL]) were absent on the left and present on the right using recording methods described previously. 1 Bone conduction ocular VEMPs were recorded using a 500-Hz tone burst (155 dB peak Force Level) delivered to the midline forehead by a handheld vibrator (Brüel & Kjaer Mini-Shaker, model 4810; Brüel & Kjaer, Naerum, Denmark) fitted with a custom acrylic rod. 2 Responses were present from the left eye and absent from the right eye at both gaze elevations (30° and maximum). The SVV angle was measured during constant on-and off-axis rotation at 300 deg/s (bilateral and unilateral centrifugation) using methods described previously. 3 The static SVV was 23°, and on-axis SVV was 25°. Off-axis rotation SVV during left and right unilateral centrifugation was 22° and 28°, respectively (Figure 1). The results of the VEMPs and centrifuga-tion SVV tests indicated a loss of otolith function on the left and normal otolith function on the right. On the basis of the vestibular test findings of an uncom-pensated unilateral vestibular loss and report of imbalance, the patient was referred for vestibular rehabilitation (VR). The patient cancelled VR, reporting an improvement in balance and the ability to return to golf. He attributed the …