We learn more every year about the effects of traumatic brain injuries and their long-lasting aftereffects. Dr. Krizman, in her presentation a couple of weeks ago, highlighted the fact that Frequency Following Response (FFR) has a distinct neural signature in young children with concussions. Even further, they noticed that their brains process the pitch of people's voices more slowly than that of children without traumatic brain injuries. Her research was a powerful demonstration of the lasting impact of traumatic brain injuries on auditory processing. I was interested in this research because we often study how TBI can impact cognitive function in the long term but seeing it from an auditory perspective was fascinating.
Following this, Theodoroff et al. (2022) paper is building this, showing how even though there are lasting auditory effects to concussion and other TBIs, it lacks clinical practice. When getting a concussion screen, no section tests any auditory subtypes, such as tinnitus, noise sensitivity, or hearing difficulties. A new paper from the TRACK-TBI study, published in the Journal of Head Trauma Rehabilitation, continues Krizman's work by examining the long-term effects of untreated auditory symptoms following TBIs. Armstrong and colleagues are asking: What are the long-term consequences of ignoring auditory symptoms after any TBI, and how can this affect the patient's cognitive function?
Using Krizman's paper as a basis, they observed a disrupted brainstem's response to the sound and how it differs from that of those without concussions. The work of Theodoroff and their team highlights the disparity and the lack of clinical knowledge used to treat the auditory symptoms of TBI's. Finally, Armstrong shows how it actively affects cognition in the long term.
The TRACK-TBI study enrolled nearly 2700 participants with various TBIs from 18 Level I trauma centers across the country, and among these, they analyzed data from 1267 participants. Two weeks post-injury, they were asked, "Since your injury, has your hearing been worse in either ear?" and among the recipients, approximately 17% responded yes. 6 months post-injury, they were given a wide range of cognitive tests, focusing on executive function called the Trail Making Test (TMT) and processing speed using the WAIS-IV Processing Speed Index.
After analyzing data from the remaining participants, they found that those with TBI-related hearing impairment at the two-week marker had significantly worse executive function at 6 months than those without hearing impairment. Those showing the most symptoms, hearing loss in both ears, and intracranial pathology in both ears, had the strongest association between the executive function level of hearing impairment following a TBI.
Even though a connection was formed linking hearing impairment from a TBH to executive function issues, none were linked to processing speed. This distinction is important because it indicates that there are only sensitivities in higher-level cognitive functioning, such as the ability to switch between tasks or to inhibit distractions.
It was interesting to read this work and compare it with Dr. Krizman's because her work highlights that the brainstem's ability to encode FFRs for sound is damaged after a brain injury. Damage to this part of the brain makes it more difficult to distinguish one sound in a busy area, meaning that the cortex has to work much harder to differentiate frequencies. The Armstrong paper highlights this by showing that many people who experienced auditory symptoms are still experiencing executive function issues six months later. In both papers, degraded sensory input makes it more difficult for the brain to process higher-order cognitive tasks, such as executive function. In total, there needs to be more research surrounding the long-term effects of concussions on executive functions. Still, more extensive screening for TBI is needed to alleviate symptoms and develop better treatment protocols.
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