title: Posture-induced changes of ocular vestibular evoked myogenic potentials suggest a modulation by intracranial pressure.
abstract: Ocular vestibular evoked myogenic potentials (oVEMPs) represent extraocular muscle activity in response to vestibular stimulation. We sought to investigate whether oVEMPs are modulated by increasing intracranial pressure (ICP). Air-conducted oVEMPs were elicited in 20 healthy subjects lying supine on a tilt table. In order to elevate the ICP, the table was stepwise tilted from the horizontal plane to a 30° declination, corresponding to a 0°, 10°, 20° and 30° head-down position. At each inclination angle, oVEMP recording was performed in two head positions: (1) the head in line with the body and (2) the head positioned horizontally with the body tilted. When tilting both the body and head, oVEMP amplitudes gradually declined from 4.59 μV at 0° to 2.24 μV at 30° head-down position, revealing a highly significant reduction in amplitudes for all tilt angles when compared to the baseline value (p < 0.001). In parallel, the response prevalence decreased and latencies prolonged. Similar effects were observed when the body was tilted but the head positioned horizontally, even though the decrease in oVEMP amplitudes was less pronounced. A gravitoinertial force effect upon the otolith organs could thereby be excluded as a possible confounder. Hence, oVEMPs were most likely modulated by increasing ICP. In the range of the horizontal plane to a 30° head-down tilt, there was a linear correlation between oVEMP amplitudes and the inclination angle. oVEMPs might in principle be suited for non-invasive ICP monitoring.
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, German Center for Vertigo and Balance Disorders, University of Munich, Grosshadern Medical Centre, Marchioninistr. 15, 81377, Munich, Germany, claudia.jerin@med.uni-muenchen.de.
authors.forename: Claudia
authors.initials: C
authors.lastname: Jerin
authors.forename: Robert
authors.initials: R
authors.lastname: Gürkov
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D011187:Posture; D011930:Reaction Time / Q000502:physiology; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*; D055815:Young Adult