Transcranial Direct Current Stimulation over the Motor or Frontal Cortex in Patients with Chronic Ankle Instability.

Objective: Growing evidence has suggested clinical efficacy for the use of anodal transcranial direct current stimulation (atDCS) when combined with motor interventions in patients with chronic ankle instability (CAI). However, no studies have compared multiple approaches for improving motor function with atDCS in patients with CAI. We therefore aimed to determine the efficacy of atDCS over the motor or frontal cortex when combined with a four-week motor planning intervention on neural function, performance, and patient-reported outcomes in patients with CAI.

Design: Double-blind, sham-controlled, parallel randomized control trial.

Methods: Participants (n=44, 15 males, 29 females, 23.6±6.1 yrs) were assessed for outcome measures of cortical and reflexive excitability; performance measures of dynamic balance, muscle activation, reaction times, and cognitive performance on a dual-task balance test; and patient-reported outcome measures at baseline, mid-training (week 2), post-training (week 4), and retention (week 6). After baseline testing, participants were randomized to receive atDCS over the motor cortex, frontal cortex, or a sham current during rehabilitation exercises over four weeks. Participants reported for eight training sessions where they were instrumented for atDCS while performing obstacle walking, dual-task balance, and agility exercises. Analyses between groups and time points were performed with mixed linear models (α=0.05).

Results: Forty-six individuals were recruited & randomized with 37 completing the investigation (motor=14, frontal=11, sham=12). No differences across groups or times were observed in neural excitability or muscle activation variables (P>0.05). Significant improvements in dynamic postural stability indices were observed from baseline across all groups (P<0.05). Improvements were observed for foot & ankle function, perceived disablement, and the Global Rating of Change at post-training and retention (p<0.001).

Conclusions: Improvements in patient function were observed across all groups, suggesting the motor planning intervention improved function, regardless of atDCS application. Observing benefits from atDCS may be dependent on proper pairing of rehabilitation exercise with electrode location.