A preliminary investigation of motor evoked potential abnormalities following sport-related concussion.

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 (<or=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 (F(3,48) = 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 (F(3,48) = 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.