Ocular vestibular evoked myogenic potentials to bone-conducted vibration in vestibular schwannomas.
BACKGROUND
Vestibular schwannoma (VS) arises from either the superior or the inferior vestibular nerve and causes vestibular dysfunction to various degrees. Recently, ocular vestibular evoked myogenic potentials to bone-conducted vibration (oVEMPs to BCV) have attracted much interest as a new clinical test for otolith-ocular pathway function. Because it is unclear whether the oVEMPs to BCV primarily originate from activation of the superior or the inferior vestibular nerve, the results in patients with VS might enlighten us concerning the origin of oVEMPs to BCV.


OBJECTIVE
To compare the results of 3 clinical tests for vestibular function in patients with VS: 1) oVEMPs to BCV; 2) cervical vestibular evoked myogenic potentials to air-conducted sound (cVEMPs to ACS), which reflect the function of inferior vestibular nerve; and 3) caloric test, which reflect the function of superior vestibular nerve.


METHODS
Thirty-six patients with unilateral VS who underwent vestibular tests, including oVEMPs to BCV, cVEMPs to ACS, and caloric tests, were enrolled. The asymmetry ratios of the amplitudes of the oVEMPs to BCV and cVEMPs to ACS and canal paresis on the caloric test were measured.


RESULTS
Among the 36 patients with VS, 31 (86%) showed reduced or absent oVEMPs to BCV. Twenty-eight patients (78%) showed abnormal cVEMPs to ACS, and 31 (86%) showed abnormal caloric responses. The consistency of the results between oVEMPs to BCV and the caloric test was significantly higher than that between oVEMPs to BCV and cVEMPs to ACS (p < 0.02).


CONCLUSIONS
Ocular vestibular evoked myogenic potentials to bone-conducted vibration mainly reflect the function of the superior vestibular nerve.
Iwasaki
Shinichi
S
Department of Otolaryngology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. iwashin-tky@umin.ac.jp
Murofushi
Toshihisa
T
Chihara
Yasuhiro
Y
Ushio
Munetaka
M
Suzuki
Mitsuya
M
Curthoys
Ian S
IS
Yamasoba
Tatsuya
T
D000328:Adult; D000368:Aged; D001844:Bone Conduction / Q000502:physiology*; D016009:Chi-Square Distribution; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000503:physiopathology*; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D018709:Statistics, Nonparametric; D014724:Vestibular Function Tests; D014725:Vestibular Nerve / Q000503:physiopathology*; D014732:Vibration