Primary Motor Cortex Excitability During Recovery After Stroke: Implications for Neuromodulation

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Neuromodulation

Background:

• Non-invasive brain stimulation aids stroke recovery by modulating cortical excitability.
• Current strategies often target ipsilesional facilitation or contralesional suppression.
• Most evidence comes from chronic stroke recovery studies.

Purpose of the Study:

• To investigate early post-stroke changes in corticomotor excitability and interhemispheric inhibition.
• To test the hypothesis of initial asymmetry in interhemispheric inhibition (contralesional to ipsilesional M1).
• To determine if balancing these measures correlates with improved paretic upper-limb function.

Main Methods:

• Retrospective analysis of longitudinal data from 46 subcortical stroke patients within six months post-stroke.
• Transcranial magnetic stimulation (TMS) used to assess motor threshold, stimulus-response curves, and silent periods.
• Statistical analyses (ANOVA, linear regression) to evaluate temporal effects and functional associations.

Main Results:

• Ipsilesional corticomotor excitability was initially suppressed but increased over time, correlating with functional gains.
• Interhemispheric inhibition remained symmetrical and stable, contrary to hypotheses.
• No significant decrease in contralesional corticomotor excitability was observed.

Conclusions:

• Direct facilitation of ipsilesional corticomotor excitability may be a key target for neuromodulation during spontaneous stroke recovery.
• Early interventions should focus on enhancing excitability in the affected hemisphere.
• Findings suggest current neuromodulation strategies might need refinement for acute/subacute stroke.