Ocular Vestibular Evoked Myogenic Potentials in Response to Bone-Conducted Vibration of the Midline Forehead at Fz
A New Indicator of Unilateral Otolithic LossIwasaki S. · Smulders Y.E. · Burgess A.M. · McGarvie L.A. · MacDougall H.G. · Halmagyi G.M. · Curthoys I.S.
aDepartment of Otolaryngology, Faculty of Medicine, University of Tokyo, Tokyo, Japan; bFaculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands; cVestibular Research Laboratory, School of Psychology, University of Sydney, and dDepartment of Neurology, Royal Prince Alfred Hospital, Sydney, N.S.W., Australia
If a patient, who is lying supine and looking upward, is given bone-conducted vibration (BCV) of the forehead at the hairline in the midline (Fz) with a clinical reflex hammer or a powerful bone conduction vibrator, short-latency surface potentials called ocular vestibular evoked myogenic potentials (oVEMP) can be recorded from just beneath the eyes. The early negative (excitatory) component (n10) is approximately equal in amplitude for both eyes in healthy subjects, but in patients with unilateral vestibular loss, the n10 component is significantly asymmetrical under the 2 eyes – the n10 component is small or absent under the eye on the side contralateral to the prior unilateral vestibular nerve removal, but of normal amplitude under the eye on the side contralateral to the healthy ear. The n10 component of the oVEMP response to BCV at Fz stimuli reflects vestibular and probably mainly otolithic function via crossed otolithic-ocular pathways, and so n10 asymmetry is a new way of identifying the affected side in patients with unilateral otolithic loss.
Bruel and Kjaer recommend that the weight of the 4810 be supported by the operator or by a separate stand so that the vibrator tip rests lightly against Fz.
Dr. Ian S. Curthoys
Vestibular Research Laboratory, School of Psychology, A 18
University of Sydney
Sydney, N.S.W. 2006 (Australia)
Tel. +61 2 9351 3570, Fax +61 2 9036 5223, E-Mail firstname.lastname@example.org
Received: December 12, 2007
Accepted after revision: April 17, 2008
Published online: July 29, 2008
Number of Print Pages : 9
Number of Figures : 3, Number of Tables : 1, Number of References : 32
Audiology and Neurotology (Basic Science and Clinical Research in the Auditory and Vestibulary Systems and Diseases of the Ear)
Vol. 13, No. 6, Year 2008 (Cover Date: October 2008)
Journal Editor: Harris J.P. (San Diego, Calif.)
ISSN: 1420–3030 (Print), eISSN: 1421–9700 (Online)
For additional information: http://www.karger.com/AUD