Sensory and motor cortical excitability changes induced by rTMS and sensory stimulation in stroke: A randomized clinical trial

Abstract

BackgroundThe ability to produce coordinated movement is dependent on dynamic interactions through transcallosal fibers between the two cerebral hemispheres of the brain. Although typically unilateral, stroke induces changes in functional and effective connectivity across hemispheres, which are related to sensorimotor impairment and stroke recovery. Previous studies have focused almost exclusively on interhemispheric interactions in the primary motor cortex (M1).ObjectiveTo identify the presence of interhemispheric asymmetry (ASY) of somatosensory cortex (S1) excitability and to investigate whether S1 repetitive transcranial magnetic stimulation (rTMS) combined with sensory stimulation (SS) changes excitability in S1 and M1, as well as S1 ASY, in individuals with subacute stroke.MethodsA randomized clinical trial. Participants with a single episode of stroke, in the subacute phase, between 35 and 75 years old, were allocated, randomly and equally balanced, to four groups: rTMS/sham SS, sham rTMS/SS, rTMS/SS, and sham rTMS/Sham SS. Participants underwent 10 sessions of S1 rTMS of the lesioned hemisphere (10 Hz, 1,500 pulses) followed by SS. SS was applied to the paretic upper limb (UL) (active SS) or non-paretic UL (sham SS). TMS-induced motor evoked potentials (MEPs) of the paretic UL and somatosensory evoked potential (SSEP) of both ULs assessed M1 and S1 cortical excitability, respectively. The S1 ASY index was measured before and after intervention. Evaluator, participants and the statistician were blinded.ResultsThirty-six participants divided equally into groups (nine participants per group). Seven patients were excluded from MEP analysis because of failure to produce consistent MEP. One participant was excluded in the SSEP analysis because no SSEP was detected. All somatosensory stimulation groups had decreased S1 ASY except for the sham rTMS/Sham SS group. When compared with baseline, M1 excitability increased only in the rTMS/SS group.ConclusionS1 rTMS and SS alone or in combination changed S1 excitability and decreased ASY, but it was only their combination that increased M1 excitability.Clinical trial registrationclinicaltrials.gov, identifier (NCT03329807).

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“…Pre-therapy, MEP were not obtained in two patients (P1 and P3) in TSEF-group and one patient (P5) in control-group, even after giving 100% Maximum Stimulator Output possibly due to decreased cortical-excitability after stroke ( Chen et al, 2008 ) and for these patients, hotspot was determined for the unaffected hand at unaffected-hemisphere and the corresponding measurements were made for the affected-hemisphere, a standard procedure described in the literature ( Chang et al, 2010 ; de Freitas et al, 2023 ). After 20 intervention-sessions in TSEF-group, patients demonstrated improvement in cortical-excitability ( Table 2 ) i.e., P1 and P3 showed the appearance of MEP at decreased RMT.…”

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“…The value after 1 month (recorded as R2) minus the baseline (recorded as R1) obtained the difference of R, i.e., d( R ). d( R ) > 0 indicates more changes in corticospinal excitability in the UH and d( R ) < 0 indicates more changes in corticospinal excitability in the AH ( Patel et al, 2020 ; de Freitas et al, 2022 ).…”

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“…The value after 1 month (recorded as R2) minus the baseline (recorded as R1) obtained the difference of R, i.e., d(R). d(R) > 0 indicates more changes in corticospinal excitability in the UH and d(R) < 0 indicates more changes in corticospinal excitability in the AH de Freitas et al, 2022).…”