Priming the motor system enhances the effects of upper limb therapy in chronic stroke

Abstract

After stroke, the function of primary motor cortex (M1) between the hemispheres may become unbalanced. Techniques that promote a re-balancing of M1 excitability may prime the brain to be more responsive to rehabilitation therapies and lead to improved functional outcomes. The present study examined the effects of Active-Passive Bilateral Therapy (APBT), a putative movement-based priming strategy designed to reduce intracortical inhibition and increase excitability within the ipsilesional M1. Thirty-two patients with upper limb weakness at least 6 months after stroke were randomized to a 1-month intervention of self-directed motor practice with their affected upper limb (control group) or to APBT for 10-15 min prior to the same motor practice (APBT group). A blinded clinical rater assessed upper limb function at baseline, and immediately and 1 month after the intervention. Transcranial magnetic stimulation was used to assess M1 excitability. Immediately after the intervention, motor function of the affected upper limb improved in both groups (P < 0.005). One month after the intervention, the APBT group had better upper limb motor function than control patients (P < 0.05). The APBT group had increased ipsilesional M1 excitability (P < 0.025), increased transcallosal inhibition from ipsilesional to contralesional M1 (P < 0.01) and increased intracortical inhibition within contralesional M1 (P < 0.005). None of these changes were found in the control group. APBT produced sustained improvements in upper limb motor function in chronic stroke patients and induced specific and sustained changes in motor cortex inhibitory function. We speculate that APBT may have facilitated plastic reorganization in the brain in response to motor therapy. The utility of APBT as an adjuvant to physical therapy warrants further consideration.

Moving rehabilitation research forward: Developing consensus statements for rehabilitation and recovery research

“…transcranial magnetic stimulation (TMS)). 19,30 TMS-based neurophysiological measures of the electrophysiological relationship(s) between the cortical hemispheres 32 and corticospinal tract integrity via the generation of motor evoked potentials relate to motor outcome in chronic 19,33 and acute stroke. 34 However, their value in predicting recovery is not well understood.…”

A review of bilateral training for upper extremity hemiparesis

“…Researchers contend that a possible neural mechanism underlying post-stroke functional improvements following bilateral training is the normalization of inhibitory mechanisms between the hemispheres (Stinear et al, 2008).…”

“…Another bilateral paradigm that has recently appeared in the literature is bilateral priming, a technique which induces cortical excitability prior to motor practice (Stinear et al, 2008). The bilateral movement is used as preparation for the brain prior to motor practice of unilateral or bilateral functional tasks.…”

“…The bilateral movement is used as preparation for the brain prior to motor practice of unilateral or bilateral functional tasks. Stinear et al (2008) reported on the fi rst bilateral priming study to date. Bilateral priming, which consisted of APBT described earlier via the 'Rocker' device, was provided to subjects for 10-15 min prior to performing tasks requiring hand dexterity.…”

P244 The effect of transcranial direct current stimulation on motor sequence learning and upper limb function after stroke

“…TCI was assessed as the ipsilateral silent period (iSP) duration from each FDI, using a TMS intensity of 80 % maximum stimulator output (MSO), similar to previous studies (Chen et al , 2003, Trompetto et al , 2004, Stinear et al , 2008, Spagnolo et al , 2013, Stinear et al , 2015. Participants were instructed to produce an isometric contraction of the FDI muscle of one hand at approximately 75 % of their maximal effort, while 20 single pulse stimuli were delivered to the ipsilateral M1.…”