Purpose: Sensory deficits are prevalent after stroke but effective interventions are limited. Non-invasive brain stimulation is a promising adjunct to peripherally administered rehabilitation therapies. However, the utility of brain stimulation in sensory re-education after stroke has not been tested. The purpose of this study was to assess immediate response to repetitive Transcranial Magnetic Stimulation (rTMS) of the contralesional primary sensory cortex (S1).
Methods: Stroke survivors (>6 mo post; n=16) with arm sensory deficits participated in 3 different rTMS treatments targeting contralesional S1 as follows: 1) Sham, 2) 5 Hz and 3) 1 Hz. rTMS was paired with peripherally directed modalities (electrical stimulation via mesh glove followed by hand vibration). rTMS paradigms were administered in random order 1 week apart. Outcomes included 2-point discrimination, vibration, monofilament discrimination and proprioception. Measures were collected before and 1 hour after treatment and responses were calculated as post minus pre for each session. Data did not appear to be normally distributed, nor were responses correlated between the 3 treatments. Kruskal-Wallis tests were employed.
Results: Subjects were 59.8±8.3 years old, 43±38 months after stroke, 88% were male and 59% had subcortical stroke. Baseline sensory impairment for the stroke Affected (A) and Unaffected (U) arms were as follows: 2-point discrimination threshold 12.47±4.73mm (A) and 2.86±1.01mm (U), monofilament 4.98±1.69mm (A) and 3.55±0.55mm (U), proprioception % accuracy at index 71.67±24.6%(A) and 99.37±1.81% (U), vibration amplitude threshold in relative units 9.7±8.6(A) and 4.75±1.8(U). There was an improvement in 2-point discrimination after 5 Hz rTMS in the affected arm; a reduced threshold of 1.68±3.5mm following 5Hz intervention vs reduction of 0.333±1.18mm after 1 Hz and increase of 0.13±2.06mm after sham (p=0.009). The unaffected arm also had improvement in 2-point discrimination of 0.38±0.8mm following 5Hz rTMS compared with increased threshold after both 1Hz (0.6±0.73mm) and sham (0.2±0.77mm) (p=0.009).
Conclusion: High frequency rTMS targeting contralesional S1 cortex is a potential adjunct intervention for sensory re-education after stroke.