Effect of multichannel transcranial direct current stimulation to reduce hypertonia in individuals with prolonged disorders of consciousness: A randomized controlled pilot study

Background: Spasticity management in severely brain-injured patients with disorders of consciousness (DOC) is a major challenge because it leads to complications and severe pain that can seriously affect quality of life. Objectives: We aimed to determine the feasibility of a single session of transcranial direct current stimulations (tDCS) to reduce spasticity in chronic patients with DOC. Methods: We enrolled 14 patients in this double-blind, sham-controlled randomized crossover pilot study. Two cathodes were placed over the left and right primary motor cortex and 2 anodes over the left and right prefrontal cortex. Hypertonia of the upper limbs and level of consciousness were assessed by the Modified Ashworth Scale (MAS) and the Coma Recovery Scale-Revised (CRS-R). Resting state electroencephalography was also performed. Results: At the group level, spasticity was reduced in only finger flexors. Four responders (29%) showed reduced hypertonicity in at least 2 joints after active but not sham stimulation. We found no behavioural changes by the CRS-R total score. At the group level, connectivity values in beta2 were higher with active versus sham stimulation. Relative power in the theta band and connectivity in the beta band were higher for responders than non-responders after the active stimulation. Conclusion: This pilot study highlights the potential benefit of using tDCS for reducing upper-limb hypertonia in patients with chronic DOC. Large-sample clinical trials are needed to optimize and validate the technique.