Background: Following stroke, the balance of primary motor cortex (M1) excitability between the cerebral hemispheres may become disturbed. Active-Passive Bilateral Therapy (APBT) is a movement-based priming strategy designed to “re-balance” M1 activity by reducing intracortical inhibition and increasing ipsilesional M1 excitability. We aimed to determine if APBT prior to physical therapy improves clinical outcome in stroke patients.
Methods: Thirty-two patients (20 men, mean age 55.3 years) with upper limb weakness at least 6 months after stroke were studied. Patients were randomized to a one-month intervention of self-directed upper limb motor practice (MP) (control group) or to APBT for 10-15 minutes prior to the same motor practice (APBT group). Upper limb function was assessed at baseline, and immediately and one-month after the intervention. Transcranial magnetic stimulation was used to assess M1 function.
Results: Affected upper limb function improved in both the control and APBT groups immediately after the intervention (p <0.005). After one-month, the APBT group demonstrated better upper limb function than control patients (p <0.05). The APBT group also had increased ipsilesional M1 excitability (p <0.025), increased transcallosal inhibition (p <0.01), and increased inhibition within contralesional M1 (p <0.005).
Conclusions: APBT produced sustained improvements in upper limb function in chronic stroke patients and induced specific and sustained changes in motor cortex 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 in larger randomized controlled trials.