Variance of vestibular-evoked myogenic potentials.
OBJECTIVE
Vestibular-evoked myogenic potential (VEMP) has been thought to originate from sacculus. The variance of this potential and the effectiveness of the adjustments of pInII amplitudes using average muscle tonus of ipsilateral sternocleidomastoid muscle were evaluated. In addition, clinical application of VEMP was examined in patients with acoustic tumors (ATs) and vestibular neurolabyrinthitis (VNL).


METHODS
Prospective evaluation of the VEMP in 18 normal volunteers and 6 patients.


METHODS
Variance and left-right difference of each parameter, including pI latency, nII latency, pInII amplitude, and threshold, was analyzed. Input-output function of pInII amplitude was evaluated. Average muscle tonus was calculated in 20 ears and applied for adjustment of pInII amplitude. Sensitivity of each parameter of VEMP was examined in 3 patients with ATs and 3 patients with VNL.


RESULTS
VEMP was present in all 36 ears of 18 control subjects. Thresholds of VEMP for normal subjects were 80 to 95 dB normal hearing level (nHL). The muscle tonus affected pInII amplitude significantly; however, no statistically significant improvement was observed in test-retest investigation after adjustment using muscle tonus. The threshold of the affected side was elevated compared with the non-affected side in all patients with ATs, whereas 2 of 3 patients showed normal pInII-ratio. One patient with VNL presented normal VEMP, whereas 2 patients presented no VEMP to the highest stimulus intensity.


CONCLUSIONS
Interaural difference of thresholds might be the most useful parameters. Adjustment using average muscle tonus is not necessary when the subject is able to get sufficient muscle tonus.
Ochi
K
K
Department of Otolaryngology, St. Marianna University School of Medicine, Toyoko Hospital, 3-435, Kosugi-cho, Nakahara-ku, Kawasaki City, Japan 211-0063. k2ochi@marianna-u.ac.jp
Ohashi
T
T
Nishino
H
H
D000161:Acoustic Stimulation; D000328:Adult; D000344:Afferent Pathways / Q000503:physiopathology; D000368:Aged; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D009334:Neck Muscles / Q000294:innervation*; D009464:Neuroma, Acoustic / Q000175:diagnosis / Q000503:physiopathology; D011237:Predictive Value of Tests; D012016:Reference Values; D012444:Saccule and Utricle / Q000503:physiopathology*; D014725:Vestibular Nerve / Q000503:physiopathology*; D020338:Vestibular Neuronitis / Q000175:diagnosis* / Q000503:physiopathology