The Effect of Combined Somatosensory Stimulation and Task-specific Training on Upper Limb Function in Chronic Stroke: a Double-blind Randomized Controlled Trial

Background: Somatosensory stimulation (SS) is a potential adjuvant to stroke rehabilitation, but the effect on function needs further investigation.

Objective: To explore the effect of combining SS with task-specific training (TST) on upper limb function and arm use in chronic stroke survivors and determine underlying mechanisms.

Methods: In this double-blinded randomized controlled trial (ISRCTN 05542931), 33 patients (mean 37.7 months poststroke) were block randomized to 2 groups: active or sham SS. They received 12 sessions of 2 hours of SS (active or sham) to all 3 upper limb nerves immediately before 30 minutes of TST. The primary outcome was the Action Research Arm Test (ARAT) score. Secondary outcomes were time to perform the ARAT, Fugl-Meyer Assessment score (FM), Motor Activity Log (MAL), and Goal Attainment Scale (GAS). Underlying mechanisms were explored using transcranial magnetic stimulation stimulus-response curves and intracortical inhibition. Outcomes were assessed at baseline, immediately following the intervention (mean 2 days), and 3 and 6 months (mean 96 and 190 days) after the intervention.

Results: The active group (n = 16) demonstrated greater improvement in ARAT score and time immediately postintervention (between-group difference; P < .05), but not at 3- or 6-month follow-ups (P > .2). Within-group improvements were seen for both groups for ARAT and GAS, but for the active group only for FM and MAL (P < .05). Corticospinal excitability did not change.

Conclusions: Long-lasting improvements in upper limb function were observed following TST. Additional benefit of SS was seen immediately post treatment, but did not persist and the underlying mechanisms remain unclear.