Hidden hearing deficits in military service members with persistent post concussive symptoms

Individuals with persistent symptoms after mild traumatic brain injury (mTBI) often have auditory complaints. In this study, we used the auditory brainstem response (ABR) to determine whether cochlear synaptopathy could explain auditory symptoms.

69 adult military service members with mTBI and 25 adults without brain injury (NCT01611194 and NCT01925963) completed pure-tone audiometry, ABR, and central auditory processing tests. All participants were male, ages 21-50.

37/69 mTBI participants had measurable hearing loss, while another 20%-30% had hearing complaints or tinnitus. While mTBI participants with measurable hearing loss had reduced wave I and III amplitude and decreased III-V interpeak latency, those with no measurable hearing loss did not significantly differ from controls on any ABR parameter. Those with measurable hearing loss were also more likely to have abnormal central auditory processing. mTBI participants with no measurable hearing loss but who reported hearing concerns had some ABR findings (III-V interpeak latency, I and V amplitudes, V/I amplitude ratio) more like the measurable hearing loss mTBI group than normative controls.

Cochlear synaptopathy may have contributed to some of the auditory impairment in service members with mTBI with measurable hearing loss. However, these results are likely confounded by cochlear hair cell damage.