Table of Contents
ISRN Anesthesiology
Volume 2011, Article ID 596848, 6 pages
http://dx.doi.org/10.5402/2011/596848
Research Article

Diagnostic Potential of Distortion Product Otoacoustic Emissions in Noninvasive Assessment of Elevated Intracranial Pressure: Different Patterns of DPOAE Alterations in the Guinea Pig

1Department of Otorhinolaryngology, Head and Neck Surgery, Technical University of Munich, Ismaningerstraße 22, 81675 Munich, Germany
2Walter Brendel Centre for Experimental Medicine, Ludwig Maximilians University of Munich, Marchioninistraße 15, 81377 Munich, Germany
3Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig Maximilians University of Munich, Marchioninistraße 15, 81377 Munich, Germany
4Department of Neurosurgery, Ludwig Maximilians University of Munich, Marchioninistraße 15, 81377 Munich, Germany

Received 31 October 2011; Accepted 5 December 2011

Academic Editors: S. Baris and E. Shipton

Copyright © 2011 Ulrich Strassen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Distortion product otoacoustic emissions (DPOAEs) have been proposed for monitoring the intracranial pressure (ICP) noninvasively. Aim of this study was to establish an animal model in the guinea pig for a detailed characterisation of ICP-related DPOAE alterations. In guinea pigs, the ICP was elevated experimentally and the DPOAE levels were continuously monitored. Two different patterns of DPOAE level changes were observed: (1) a decrease of few decibels affecting mainly the frequency 𝑓 2 = 2 kHz with instant recovery after normalization of ICP, probably related to alterations of middle ear sound transmission; (2) a more pronounced level decrease affecting all frequencies, combined with a second decrease and prolonged recovery after ICP normalization, which might be related to alterations of the cochlear blood flow. Alterations of the levels of DPOAEs might not only provide information about ICP but also indicate critical ICP-induced reductions of the cochlear and the cerebral perfusion pressure.