Introduction: Transcranial direct current stimulation (tDCS) and somatosensory stimulation in the form of peripheral sensory stimulation (PSS) have emerged as potential powerful tools to enhance motor performance or increase effects of motor training in stroke victims.
Objectives: To compare effects of active PSS+tDCS, tDCS alone, PSS alone and sham PSS+tDCS as add-on interventions to motor training in patients with stroke and moderate to severe upper limb impairments.
Methods: Patients > 6 months post-stroke underwent four different interventions, in a cross-over design: repetitive training of wrist extension of the paretic arm preceded by either active PSS (median, ulnar and radial nerves), active anodal tDCS of the affected hemisphere, sham PSS+tDCS or active PSS+tDCS. Before and after each session, the following outcomes were blindly evaluated in the paretic upper limb: range of movement (ROM) of wrist extension (primary outcome); ROM of wrist flexion, grasp and pinch strength. Measures were compared with analysis of variance with repeated measures (ANOVARM) with factors “session” and “time”.
Results: After screening 2499 patients, 22 subjects were included in the study (14 men). The mean age (± standard deviation) was 55.2±12.9 years and the mean time from stroke, 5.3±5.6 years. The mean Fugl-Meyer score for the paretic upper limb was 37±7.9. Two patients were excluded (one dropped out and one received botulinum toxin treatment). There was a significant effect of “time” (F=4.6, p=0.046), but no effects of “session” or interaction “session x time” in regard to grasp force. There were no significant effects of “session”, “time” or interaction “session x time” in regard to ROM of wrist extension, wrist flexion, or pinch force.
Conclusions: Repetitive training of wrist extension specifically improved grasp force and did not influence other outcomes. PSS+tDCS, tDCS alone or PSS alone did not potentiate the effect of training.