The cubic distortion product otoacoustic emissions from the normal and noise-damaged chinchilla cochlea

Abstract

A normative study of the cubic distortion product emissions from 104 monaural and binaural chinchillas was undertaken to establish criteria upon which noise exposed animals could be evaluated. From this normative group, 47 randomly selected chinchillas were exposed to various high level (150-, 155-, and 160-db peak SPL) impulse noises. Auditory evoked potentials and cubic distortion product otoacoustic emissions were measured on each animal pre- and post-exposure and related to the sensory cell populations 30 days post-exposure. Both group mean and individual animal data indicated that the distortion product emissions were more sensitive, frequency-specific indices of noise-induced cochlear effects than pure-tone threshold measures. This was particularly evident near the threshold for noise-induced damage to the outer hair cell system.

The effect of impulse noise exposure on distortion product otoacoustic emissions in the awake guinea pig

“…We believe that this reduction was due to damage of the OHC but not to damage of the inner hair cells [9,10,13,25,26]. In the previous studies reported morphological changes were compared after impulse noise exposure of 164 and 153 dB pe SPL [20,22].…”

“…For these reasons it is necessary to investigate the occurrence of DPOAE further in experimental models with defined damage to the OHC. Indeed, experiments in animals have shown that it is possible to evoke and measure DPOAE as well as transiently evoked (TE) emissions and that these are influenced by ototoxic drugs, noise exposure and hypoxia [4,9,10,13,14].…”

“…In particular, they are used for the early and differential diagnosis of damage to the outer hair cells [9,11,26]. This objective non-invasive method allows the clinician to examine cochlear function in non-cooperative patients, as well as to monitor inner ear function after the use of ototoxic drugs and to detect damage to outer hair cells (OHC) after noise exposure.…”

“…It has been observed that the diagnostic outcome of the pure-tone audiogram and the measurement of OAEs may differ [5,9,26,27]. Firstly, DPOAE may not be altered after moderate hearing loss [28,29].…”

Erholung der H�rschwelle nach Knalltrauma durch Feuerwerksk�rper und Signalpistolen

“…Auch konnte eine mögliche Vorschädi-gung des Gehörs -bis auf einzelne Fälle -aufgrund mangelnder audiometrischer Vorbefunde nur anamnestisch, nicht jedoch quantitativ ausgeschlossen werden. Selbst das Vorliegen von Normalbefunden im Reintonaudiogramm vor Exposition mit Impulslärm wäre allerdings letztendlich nicht ausreichend, da das Tonaudiogramm zwar den Standard für die Hörschwellenbestimmung darstellt, aber trotz einer Erholung der Hörschwel-le im Reintonaudiogramm subtile Innenohrschäden zurückbleiben können und somit trotz normaler Hörschwelle im Tonaudiogramm eine Vorschädigung vorliegen kann [3].…”