Assessment of motor cortex excitability and inhibition during a cognitive task in individuals with concussion.

PRIMARY OBJECTIVE: To examine the function of the motor cortex during executive function tasks in individuals with concussion, relative to healthy controls.

METHODS AND PROCEDURES: Transcranial magnetic stimulation (TMS) was used to assess motor cortex excitability and inhibition acutely, within 72 hours, and over two months, post-concussion in 23 participants, nine individuals with concussion and 14 controls. Participants performed a cognitive task during TMS to determine the impact of cognitive task on the motor cortex.

MAIN OUTCOMES AND RESULTS: Resting motor threshold (p = 0.02) and motor-evoked potential (MEPRest ) amplitude (p = 0.03) were different between groups, both suggesting greater corticospinal excitability in individuals with concussion. Cortical silent period (CSP) duration was greater at 72 hours (p = 0.03), one month (p = 0.003) and two months (p = 0.05) in individuals with concussion, suggesting increased intracortical inhibition. The performance of a cognitive task caused an increase in MEPRest (p = 0.006) and CSP (p = 0.04), compared to baseline in both groups, but no interaction of condition by group (p ≥ 0.91) for either measure.

CONCLUSION: Simultaneously performing a cognitive task during motor cortex assessments increased corticospinal excitability and intracortical inhibition; however, the increase was not different between groups.