Effect of head position on vestibular evoked myogenic potentials with toneburst stimuli.
CONCLUSIONS
The present study demonstrated the robustness of VEMP testing with toneburst stimuli, since it is hardly affected by head position, i.e. base or tonic excitation levels of the saccule and inferior vestibular nerve. However, the small but highly significant difference found in latency should not be neglected: the gravitational axis in the upright position may have some special effect on tonic excitation of the saccule.


OBJECTIVE
To evaluate the effect of head positions on vestibular evoked myogenic potentials (VEMPs) with toneburst stimuli.


METHODS
VEMPs were recorded with short tonebursts of 500 Hz in 14 normal subjects in 5 head positions (upright, nose up, ear up, nose down, and ear down). The three parameters analyzed were: 1) latency of p13, 2) latency of n23, and 3) corrected amplitude of p13-n23 (CA p13-n23).


RESULTS
One-way repeated measures ANOVA showed significant effects on both p13 (p=0.0245) and n23 (p<0.0001) latencies, but not on CA p13-n23. Bonferroni's post hoc test demonstrated that there were significant differences in n23 latency between the upright position and all other head positions leaning on the bed.
Ito
Ken
K
Department of Otolaryngology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. itoken@-tky@umin.ac.jp
Karino
Shotaro
S
Murofushi
Toshihisa
T
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D004576:Electromyography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006112:Gravitation; D006257:Head; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation; D011187:Posture; D012399:Rotation; D014722:Vestibule, Labyrinth / Q000502:physiology*