Non-paretic leg movements can facilitate cortical drive to the paretic
leg in severe stroke: implications for motor priming
Abstract
Background: Cross-education, a phenomenon where unilateral strength (or
skill) training enhances strength (or skill) in the contralateral
untrained limb, has been well studied in able-bodied individuals.
However, whether non-paretic leg movements can modulate corticomotor
excitability (CME) and improve motor control of the paretic leg in
stroke remains unclear. Objective: To determine the effects of
non-paretic leg movements on corticomotor responses and motor control of
the paretic leg in persons with severe stroke. Methods: Seventeen post
stroke individuals with severe leg motor impairment performed three
20-min motor trainings using their non-paretic ankle: skill (targeted
dynamic movements), strength (isometric resistance), and sham
(sub-threshold electrical nerve stimulation). Transcranial magnetic
stimulation measured CME of the contralateral pathways from the
non-lesioned motor cortex (M1) to the non-paretic tibialis anterior (TA)
muscle, ipsilateral pathways to the paretic TA, and transcallosal
inhibition (TCI) from the non-lesioned to lesioned M1. Paretic ankle
motor control was measured using a reaction time paradigm. Results: CME
of the non-paretic TA increased after skill (23%) and strength (19%)
training (p<0.01). Ipsilateral CME of the paretic TA (23%)
and TCI (36%) increased after skill (p<0.05) but not strength
training. Reaction time of the paretic ankle improved after skill and
strength training (~12%; p<0.05) and was
sustained at 60 minutes. No changes were observed during the sham
condition. Conclusion: Our findings may inform future studies for using
non-paretic leg movements as a priming modality, especially for those
who are contraindicated to other priming paradigms (e.g., brain
stimulation) or unable to perform paretic leg movements.