Vulnerability to acoustic trauma in the normal hearing ear with contralateral hearing loss.

Abstract

OBJECTIVES:

We undertook an animal study to investigate the functional and histological changes that occur in the normal hearing ear of following acoustic trauma.

METHODS:

As an animal model of unilateral hearing loss, the right ears of CBA mice were deafened by cochlear destruction at 6 weeks of age (SSD group). The control groups included mice that underwent a sham surgery, and mice that were exposed to noise binaurally and monaurally (by plugging the right ear completely). At 10 weeks of age, all mice were exposed to acoustic trauma (110 dB sound pressure level for 1 hour) that induced a transient threshold shift (TTS). Changes in the hearing thresholds of the left ear were assessed over the next 4 weeks by measuring the auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs).

RESULTS:

Following the noise exposure, the SSD group showed a permanent threshold shift (PTS) of about 10 dB, whereas the other groups showed full recovery from the TTS. The threshold of the DPOAEs of the left ears were increased after noise exposure but returned to normal in all groups, with no significant differences among the groups. Histological evaluation showed no apparent cellular loss or apoptosis in the left ears of all groups, including the SSD group.

CONCLUSIONS:

These results suggest that normal hearing ears are more vulnerable to acoustic trauma following contralateral unilateral cochlear ablation. This increased vulnerability may be due to damaged neural structures.

• Authors: Hyun Woo Lim, Ji Won Lee, Jong Woo Chung
• Journal: The Annals of otology, rhinology, and laryngology (Ann Otol Rhinol Laryngol) Vol. 123 Issue 4 Pg. 286-92 (Apr 2014) ISSN: 0003-4894 [Print] United States
• PMID: 24671484 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Topics

• Animals
• Auditory Threshold
• Cochlea (pathology, physiopathology)
• Disease Models, Animal
• Disease Susceptibility
• Evoked Potentials, Auditory, Brain Stem
• Hearing Loss, Noise-Induced (etiology, pathology, physiopathology)
• Hearing Loss, Unilateral (etiology, pathology, physiopathology)
• Mice, Inbred CBA
• Otoacoustic Emissions, Spontaneous