Ocular vestibular-evoked myogenic potentials (oVEMPs) require extraocular muscles but not facial or cochlear nerve activity.
OBJECTIVE
Cervical vestibular evoked myogenic potentials (cVEMPs) have been found to be useful for clinical testing of vestibular function. Recently, investigators showed that short-latency, initially negative surface EMG potentials can be recorded around the extraocular muscles (oVEMPs) in response to air-conducted sound (ACS), bone-conducted vibration (BCV), and head taps. Although these evoked potentials, which are located around the eyes, most likely originate primarily from the otolith-ocular pathway, the possibility of contamination by other nerve activities cannot be completely eliminated. The purpose of the present study was to clarify the origin of oVEMPs by examining these possibilities using clinical findings.


METHODS
Twelve healthy subjects and 15 patients were enrolled. Of the 15 patients, 3 patients had undergone exenteration of the unilateral intraorbital contents, one had undergone exenteration of the right eyeball with preservation of extraocular muscles, 5 had facial palsy, and 6 had profound hearing loss. ACS and/or BCV were used in these subjects.


RESULTS
Exenteration of the unilateral intraorbital contents resulted in absence of myogenic potentials on the affected side. On the other hand, exenteration of the eyeball with preservation of extraocular muscles did not have a major impact on the responses. There were no significant differences in the waveforms between healthy subjects and patients with facial palsy or profound hearing loss.


CONCLUSIONS
The results suggested that short-latency, initially negative evoked potentials recorded below the eyes are not affected by cochlear or facial nerve activities and are dependent on the presence of extraocular muscles.


CONCLUSIONS
This study provides the evidence that oVEMPs originate from exraocular muscles activated through the vestibulo-ocular pathway.
Chihara
Yasuhiro
Y
Department of Otolaryngology-Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113-8655 Tokyo, Japan. y-chihara@umin.ac.jp
Iwasaki
Shinichi
S
Ushio
Munetaka
M
Fujimoto
Chisato
C
Kashio
Akinori
A
Kondo
Kenji
K
Ito
Ken
K
Asakage
Takahiro
T
Yamasoba
Tatsuya
T
Kaga
Kimitaka
K
Murofushi
Toshihisa
T
D000161:Acoustic Stimulation; D000328:Adult; D003056:Cochlear Nerve / Q000502:physiology; D004576:Electromyography; D005071:Evoked Potentials / Q000502:physiology*; D005154:Facial Nerve / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009334:Neck Muscles / Q000294:innervation / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009801:Oculomotor Muscles / Q000294:innervation / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology; D010812:Physical Stimulation; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D014722:Vestibule, Labyrinth / Q000502:physiology*; D014732:Vibration