The Effects of Transcranial Direct Current Stimulation on Chronic Ankle Instability

Purpose Given maladaptive neuroplasticity after musculoskeletal injury, interventions capable of restoring corticospinal excitability should be considered. We therefore aimed to determine if a 4-wk intervention of anodal transcranial direct current stimulation (aTDCS) with eccentric exercise would improve neural excitability, functional performance, and patient-reported function in individuals with chronic ankle instability (CAI). Methods Twenty-six individuals with CAI were recruited to undergo 4 wk of eccentric evertor strengthening. Subjects were randomized into aTDCS (n = 13) and sham (n = 13) groups, where the aTDCS group received 18 min of aTDCS (1.5 mA) over the primary motor cortex. Participants were assessed for cortical excitability, dynamic balance, muscle activation, functional performance, strength, and patient-reported function at baseline, week 2, week 4, and week 6. Results Twenty-two subjects completed the training and test sessions. Cortical excitability (resting motor threshold) to peroneus longus in aTDCS increased from baseline (36.92 11.53) to week 6 (32.91 +/- 12.33, P = 0.024), whereas sham increased excitability from baseline (36.67 +/- 12.74) to week 2 (27.86 +/- 14.69, P = 0.007), but decreased at week 4 (35.63 +/- 13.10, P = 0.022) and week 6 (35.99 +/- 13.52, P = 0.006). Dynamic balance and muscle activation also improved in the aTDCS group from baseline to week 6 (P = 0.034). Functional performance on a side-hop test increased in all participants from baseline to week 2 (P = 0.003). The aTDCS group had decreased perceived disablement from week 2 (18.09 +/- 6.41) to week 4 (15.55 +/- 4.82, P = 0.046), whereas the sham group reported increased disablement from baseline (17.91 +/- 4.59) to week 2 (21.00 +/- 8.52, P = 0.047). Conclusions Our results provide preliminary evidence that 4 wk of eccentric training with aTDCS improves cortical excitability, functional performance, and patient-reported function in individuals with CAI. These data are the first to show the efficacy of noninvasive brain stimulation therapies in patients with musculoskeletal injury, and demonstrate the link between improved neural excitability and functional outcomes.