Priming with transcutaneous spinal direct current stimulation followed by robotic exoskeleton gait training in individuals with spinal cord injury: A case series.

Objectives: To investigate the safety and feasibility of repeated transcutaneous spinal direct current stimulation (tsDCS) as priming strategy during exoskeleton-assisted locomotor training in individuals with SCI and evaluate potential neurophysiologic and functional gait changes.

Study design: Case series experimental design.

Setting: Research laboratory at a post-acute rehabilitation hospital.

Participants: Four participants with chronic incomplete SCI.

Interventions: Four participants with chronic incomplete SCI received three weeks of training consisting of two types of interventions after baseline (A): 20-minute tsDCS (anode or cathode) applied over the spinous processes of T10 followed by 20-minute exoskeleton-assisted locomotor training (B, B1, B2) and 20-minute exoskeleton-assisted locomotor training (C, C1, C2). Each phase consisted of five consecutive intervention sessions. Two participants underwent sequence A-B1-C-B2 and two sequence A-C1-B-C2. Soleus Hoffmann Reflex (H-reflex) and gait speed (10-m walk test) were assessed on the first and fifth days of training for each training type.

Outcome measures: Adverse skin reactions or other events, H-reflex (Hmax/Mmax ratio), and gait speed (10-m walk test).

Results: No adverse events occurred. All participants tolerated tsDCS with no negative effects on their skin. Participants demonstrated varied responses in their H/M ratios after tsDCS followed by exoskeleton-assisted locomotor training as well as after exoskeleton-assisted locomotor training. No consistent pattern can be identified in this case series. Three participants showed an increase in gait speed after tsDCS combined with exoskeleton-assisted locomotor training.

Conclusions: Noninvasive repeated spinal stimulation can safely be used in individuals with incomplete SCI. Further large-scale research is necessary to determine the efficacy of tsDCS for priming the spinal cord in facilitating recovery of gait in individuals with SCI.