Relationship Between Descending Neural Drives from the Non-Injured Hemisphere and Lower Limb Motor Function and Gait Ability in Patients Following Severe Stroke.

BackgroundThe relationship between the functional recovery of patients in the subacute phase of stroke and descending neural drives from the non-injured hemisphere to the paretic lower limb muscles during movement remains unclear. We investigated this relationship in patients with severe paralysis.MethodsTwenty-nine patients with stroke were recruited and categorized into three groups based on paralysis severity. Within 1 month of admission, each patient received 10 min of anodal tDCS applied to the cortical motor areas of the injured or non-injured hemispheres. Each stimulation condition was performed in a random order, one day at a time, with a 7-day washout period. Before and after each stimulation, patients performed multiple voluntary knee extensions on the paretic side 20% of their maximal strength, sustained for 6 s. Coherence analysis of EMG signals from proximal and distal segments of the vastus medialis muscle was conducted to quantify common neural drive from each cortical motor-related area based on coherence variations before and post stimulation in each condition. We investigated the relationship between the excitability of the descending neural pathway from the non-injured hemisphere in the initial phase and motor function recovery at 3 months.ResultsNo significant differences emerged across groups in the change in coherence values when the non-injured hemisphere stimulated. However, within the severe group, an increase in β-band coherence following non-injured hemisphere stimulation correlated with greater recovery of paretic-side muscle strength and trunk function at 3 months.ConclusionOur findings deepen understanding of paralysis pathophysiology based on severity level and may support the development of targeted neuromodulation strategies to enhance motor recovery.