Acute and longitudinal changes in motor cortex function following mild traumatic brain injury

Abstract

Primary objective: To evaluate excitability and inhibition of the motor cortex acutely and longitudinally following mild traumatic brain injury (mTBI).

Research design: A longitudinal paired case-control design was used to examine cortical excitability and inhibition in 15 adults who had sustained an mTBI (mean age = 20.8 ± 1.2 years) and 15 matched control participants (mean age = 21.1 ± 1.3 years).

Methods and procedures: Participants visited the lab within 72 hours of injury and again at 1, 2, 4 and 8 weeks post-injury. During each visit, transcranial magnetic stimulation was used to examine resting motor threshold (RMT), motor evoked potential peak-to-peak amplitude (MEP_amp) and cortical silent period (CSP) duration of the first dorsal interosseous muscle.

Main outcomes and results: There were no differences between groups in RMT (p = 0.10) or MEP_amp (p = 0.22) at 72 hours post-injury or across the 2-month testing period (p ≥ 0.68), indicating similar cortical excitability. However, the CSP duration was higher in individuals with mTBI, indicating greater intra-cortical inhibition compared with the control group at 72 hours post-injury (p = 0.03) and throughout the 2 months of recovery (p = 0.009).

Conclusions: mTBI appeared to have little effect on cortical excitability, but an acute and long-lasting effect on intra-cortical inhibition.

• Evoked potentials
• mild traumatic brain injury
• neurobehavioural

Acknowledgements

The authors wish to thank Holly Calderon, Eli Edwards and Josh Sweigert for contributions in data collection and analysis.