Does rTMS Targeting Contralesional S1 Enhance Upper Limb Somatosensory Function in Chronic Stroke? A Proof-of-Principle Study

Background Somatosensory deficits are prevalent after stroke, but effective interventions are limited. Brain stimulation of the contralesional primary somatosensory cortex (S1) is a promising adjunct to peripherally administered rehabilitation therapies. Objective To assess short-term effects of repetitive transcranial magnetic stimulation (rTMS) targeting contralesional (S1) of the upper extremity. Methods Using a single-session randomized crossover design, stroke survivors with upper extremity somatosensory loss participated in 3 rTMS treatments targeting contralesional S1: Sham, 5 Hz, and 1 Hz. rTMS was delivered concurrently with peripheral of sensory electrical stimulation and vibration of the affected hand. Outcomes included 2-point discrimination (2PD), proprioception, vibration perception threshold, monofilament threshold (size), and somatosensory evoked potential (SEP). Measures were collected before, immediately after treatment, and 1 hour after treatment. Mixed models were fit to analyze the effects of the 3 interventions. Results Subjects were 59.8 ± 8.1 years old and 45 ± 39 months poststroke. There was improvement in 2PD after 5-Hz rTMS for the stroke-affected ( F(2, 76.163) = 3.5, P = .035) and unaffected arm ( F(2, 192.786) = 10.6, P < .0001). Peak-to-peak SEP amplitudes were greater after 5-Hz rTMS for N33-P45 ( F(2, 133.027) = 3.518, P = .032) and N45-P60 ( F(2, 67.353) = 3.212, P = .047). Latencies shortened after 5-Hz rTMS for N20 ( F(2, 69.64) = 3.37, P = .04), N60 ( F(2, 47.343) = 4.375, P = .018), and P100 ( F(2, 37.608) = 3.537, P = .039) peaks. There were no differences between changes immediately after the intervention and an hour later. Conclusions Short-term application of facilitatory high-frequency rTMS (5Hz) to contralesional S1 combined with peripheral somatosensory stimulation may promote somatosensory function. This intervention may serve as a useful adjunct in somatosensory rehabilitation after stroke.