A 2016 study sought to determine whether concussions predictably affect pitch perception, sound identification, and speech processing in children. The study found that children with concussions respond inadequately to changes in pitch and display a distinct profile of impaired sound processing.
Presently, the diagnosis of concussions – mild brain injuries sustained after forceful blows to the head or neck, which can impair concentration, balance, coordination, memory, and emotional responses – is fairly subjective, relying heavily on the breadth and accuracy of a patient’s report of the symptoms they have been experiencing. Making an accurate diagnosis can, therefore, be especially challenging when dealing with child patients. As such, objective and distinct indicators of concussive brain damage would help physicians correctly identify the disease in patients and better outline a path to recovery. As mild traumatic brain injuries such as concussions are associated with difficulty making sense of sounds, identifying reliable measures of concussion-specific sound perception and processing difficulties may provide a basis for the development of effective tools for the diagnosis of concussions.
In a 2016 study published in Scientific Reports, researchers sought to determine whether concussions predictably affect the ability of child concussion patients to perceive pitch, identify sounds, and recognize rhythms, stresses, and intonations in speech. Twenty children clinically diagnosed with a concussion – 6 boys and 14 girls, average age 13.39 years – were recruited from a sports medicine clinic in Chicago. Thirteen reported previously having a brain injury. Non-concussed controls with no history of brain injury – 6 boys and 14 girls, average age 13.64 years – were recruited from the community. Eleven in the concussed group – 3 boys and 8 girls, average age 13.25 years – were retested 11-54 days after their initial examination. Normal hearing was confirmed by measuring changes in voltage generated by the brainstem when exposed to 80.4 dB clicks, and by registering the low level sounds naturally generated by the inner ear that are indicative of structures crucial to hearing.
Sound perception was determined by measuring changes in voltage generated by the brainstem (responses) to sound recordings, especially the frequency-following response (FFR) for each subject – the ability to identify a difference between certain voiceless and voiced consonant sounds, e.g. the change from a voiceless, percussive d sound to a voiced, sustained d sound. After hearing recordings of voiceless consonant sounds followed by their corresponding voiced consonant sounds, all played against various levels of background noise, responses and response times were recorded. The fundamental frequency (F0) – a basic component of pitch – which increases as a consonant sound moves from voiceless to voiced, was recorded for each transition. The severity of 19 concussion symptoms were scored from 0-6 (with 6 representing great intensity) and added together to produce an overall severity score for each concussion patient.
Though the pattern of sensitivity to the different frequencies against background noise was similar in both groups, sensitivity, F0 responses, and FFRs were greater in the control group than in the concussion group. Those with more severe symptoms were less sensitive to changes in F0. For those retested, all of whose symptoms improved, F0 responses increased 30%, falling within the range of the control group. Response times for the beginning of sounds, the transition between the percussive and sustained aspects of voiced consonant sounds, and the endings of sounds were the same for both groups. Response times with respect to vocal variations were slightly longer for the concussion group. In addition, using the FFR as a diagnostic measure correctly categorized 18 of the 20 concussion group patients (90%) and 19 out of the 20 control patients (95%).
Overall, the results of this study suggest that sensitivity to the F0 of a sound is lower and brainstem responses to it are weaker, less accurate, and slower in children with concussions than in their uninjured counterparts. Consequently, it may be that children with concussions respond inadequately to changes in pitch and process speech less effectively. The high accuracy of the FFR as an indicator of belonging to the concussion group in this study suggests it may serve as an effective basis for diagnostic tools in the future. Further research with larger sample sizes will be required to determine whether the FFR can be used to distinguish concussions from similar mild traumatic brain injuries. As the concussion group was recruited from a sports medicine clinic – to which patients are referred to receive specialized treatment – the concussive symptoms represented may have been more severe than those which might have been observed had patients been recruited from a hospital. Future research would also benefit from a larger, sex-balanced study population in order to obtain conclusive results.
Written By: Raishard Haynes, MBS