Dysfunction of the auditory efferent system in patients with traumatic brain injuries with tinnitus and hyperacusis.

Tinnitus, hyperacusis and difficulty listening in background noise are common symptoms reported by patients with traumatic brain injury (TBI). The aim of this study was to explore the function of the auditory system in TBI patients with and without auditory complaints but having normal pure-tone audiograms.The study consisted of 24 TBI patients with and 10 TBI patients without auditory complaints. In addition, 15 normal controls were included in the study. The function of the auditory system was tested by recording transient otoacoustic emissions (TEOAE) during the presentation of increasing levels of white noise in the contralateral ear.Most of the TBI patients with auditory complaints (87%) showed absent or significantly reduced effect of the auditory efferent system as compared with the TBI patients without auditory complaints and to normal controls. However, the global amplitude of the TEOAE was significantly higher in TBI patients with auditory complaints compared to those without.Due to its role in peripheral and central auditory activity, dysfunction of the efferent system may be at least partially responsible for these auditory complaints. This study underscores the importance of testing and evaluating the functional integrity of the medial efferent system by an objective and non-invasive method in patients with TBI.