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Abstract
Background: Assessment of concussion is primarily based on self-reported symptoms, neurological examination and neuropsychological testing. The neurophysiologic sequelae and the integrity of the corticomotor pathways could be obtained by evaluating motor evoked potentials (MEPs).
Objectives: To compare MEPs obtained through transcranial magnetic stimulation (TMS) in acutely concussed and non-concussed collegiate athletes.
Methods: Eighteen collegiate athletes (12 males, six females, aged 20.4 ± 1.3 years) including nine subjects with acute concussion (≤24 hours) matched to nine control subjects. TMS was applied over the motor cortex and MEP responses were recorded from the contralateral upper extremity. MEP thresholds (%), latencies (milliseconds per metre) and amplitudes were assessed. Central motor conduction time (CMCT) was calculated from MEP, M response and F wave latencies. Testing was performed on days 1, 3, 5 and 10 post-concussion.
Results: Ulnar MEP amplitudes were significantly different between post-concussion days 3 and 5 (F3,48 = 3.13, p = 0.041) with smaller amplitudes recorded on day 3 (0.28 ± 0.10 ms m−1). Median MEP latencies were significantly longer (F3,48 = 4.53, p = 0.023) 10 days post-concussion (27.1 ± 1.4 ms m−1) compared to day 1 (25.7 ± 1.5 ms m−1). No significant differences for motor thresholds or CMCTs were observed (p > 0.05).
Conclusion: MEP abnormalities among acutely concussed collegiate athletes provide direct electrophysiologic evidence for the immediate effects of concussion.