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

Ulrich Strassen,Klaus Mees,Martin Canis,Christoph Deppe,Bernhard Olzowy,Nikolaus Plesnila,Sebastian Strieth

doi:10.5402/2011/596848

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 = 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.

Highlights

Elevated intracranial pressure (ICP) can complicate the course of several common pathologies such as head injury, intracranial hemorrhage, hydrocephalus, stroke, hypoxic brain injury, central nervous system infection, and acute liver failure
Two different patterns of Distortion product otoacoustic emissions (DPOAEs) level changes were observed: (1) a decrease of few decibels affecting mainly the frequency f2 = 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
An increase of the cerebrospinal fluid (CSF) pressure, results in increased pressure on the stapes footplate and, in an altered sound transmission through the middle ear [3,4,5], which can sensitively be detected by DPOAEs

Summary

Introduction

Elevated intracranial pressure (ICP) can complicate the course of several common pathologies such as head injury, intracranial hemorrhage, hydrocephalus, stroke, hypoxic brain injury, central nervous system infection, and acute liver failure. The external ventricular drain and parenchymal probes are commonly used for monitoring the ICP. Both procedures are cost-intensive, invasive, and carry a risk of hemorrhage and infection [1]. An increase of the CSF pressure, results in increased pressure on the stapes footplate and, in an altered sound transmission through the middle ear [3,4,5], which can sensitively be detected by DPOAEs. In humans, elevation of the ICP induces a decrease of the DPOAE levels most pronounced at the frequencies between 0.75 and 2 kHz while higher frequencies only show minor changes [3, 6, 7].

Methods

Results

Conclusion