The Effect of Increasing Intracranial Pressure on Ocular Vestibular-Evoked Myogenic Potential Frequency Tuning.
OBJECTIVE
Ocular vestibular-evoked myogenic potentials (oVEMPs) represent extraocular muscle activity in response to vestibular stimulation. The authors sought to investigate whether posture-induced increase of the intracranial pressure (ICP) modulated oVEMP frequency tuning, that is, the amplitude ratio between 500-Hz and 1000-Hz stimuli.


METHODS
Ten healthy subjects were enrolled in this study. The subjects were positioned in the horizontal plane (0 degree) and in a 30-degree head-downwards position to elevate the ICP. In both positions, oVEMPs were recorded using 500-Hz and 1000-Hz air-conducted tone bursts.


RESULTS
When tilting the subject from the horizontal plane to the 30-degree head-down position, oVEMP amplitudes in response to 500-Hz tone bursts distinctly decreased (3.40 μV versus 2.06 μV; p < 0.001), whereas amplitudes to 1000 Hz were only slightly diminished (2.74 μV versus 2.48 μV; p = 0.251). Correspondingly, the 500/1000-Hz amplitude ratio significantly decreased when tilting the subjects from 0- to 30-degree inclination (1.59 versus 1.05; p = 0.029). Latencies were not modulated by head-down position.


CONCLUSIONS
Increasing ICP systematically alters oVEMPs in terms of absolute amplitudes and frequency tuning characteristics. oVEMPs are therefore in principle suited for noninvasive ICP monitoring.
1German Center for Vertigo and Balance Disorders, Grosshadern Medical Center, University of Munich, Munich, Germany; 2Department of Medicine I, Klinikum Grosshadern, University of Munich and Munich Heart Alliance (Deutsches Zentrum für Herz-Kreislauf-Forschung), Munich, Germany; 3Department of Neurology, Inselspital Bern, Bern, Switzerland; and 4Department of Otorhinolaryngology-Head and Neck Surgery, Grosshadern Medical Center, University of Munich, Munich, Germany.
Claudia
C
Jerin
Reza
R
Wakili
Roger
R
Kalla
Robert
R
Gürkov
D000328:Adult; D004576:Electromyography; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology*; D006801:Humans; D019586:Intracranial Hypertension / Q000503:physiopathology*; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*; D055815:Young Adult