Self-Reported Symptoms of Central Auditory Processing Dysfunction Following Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI), also known as concussion, has emerged as a major public health concern in the United States and worldwide. Of the estimated 1.7 million head injuries that occur nationally each year, about 75% are mTBI. Despite the “mild” label, a significant percentage of these individuals continue to experience a wide array of life-altering physical, emotional, and cognitive post-concussion symptoms for months and years following injury. The central auditory nervous system is vulnerable to several injury mechanisms in TBI and, as a result, auditory problems can be among these long term problems. Although evidence of auditory processing problems following traumatic brain injury has been reported across a growing number of published case reports and group studies, few studies have investigated the prevalence of such problems due specifically to mTBI. The purpose of this study was to determine whether symptoms consistent with central auditory processing problems were among the persistent post-concussive symptoms seen in those individuals who experience long-term problems. Symptoms of auditory processing dysfunction in a group of mTBI subjects (n = 32) were compared to those reported by un-injured control subjects (n = 27). Participants completed self-reported symptom questionnaires in both auditory and other post-concussion symptom domains. Twelve of the 32 mTBI subjects also completed a mailed follow up including a repeat of the auditory processing questionnaire several months later to evaluate changes in symptoms over time. This same subset also completed an additional hearing disability scale, and results were compared to published data from 1) normal hearing younger and older adults and 2) hearing impaired older adults to investigate how much concussion influenced such symptoms. Consistent with our hypotheses, individuals with mTBI reported significantly more symptoms of auditory processing difficulty than the ageand gender-matched controls. Some of the highest reported difficulties for mTBI subjects included difficulty listening in background noise, sensitivity to loud sounds, and difficulty understanding rapid speech. Scores from the auditory processing questionnaire were highly correlated with post-concussion symptoms in all the other domains, including depression, fatigue, anxiety, post-traumatic stress, and general concussion symptoms. For the subset of mTBI subjects who completed the auditory processing questionnaire a second time, all of the subjects continued to experience auditory processing symptoms several months to more than two years post-injury. Overall, the mTBI subjects who completed the hearing disability scale had mean scores that indicated more difficulty with speech understanding, spatial location, and perceived quality of speech than did groups of both younger and older normal-hearing adults (without head injury) from published normative studies. Compared to adults with peripheral hearing loss, however, the mTBI group in the current study had slightly better mean scores, consistent with fewer auditory problems. These results suggest that auditory processing difficulties do pose a problem for individuals with mTBI who continue to experience long-term problems after concussion. Further research is needed to determine whether these self-reported symptoms of auditory processing difficulty