Transcallosal inhibition does not influence subacute motor recovery in mild-to-moderate stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Motor Recovery

Background:

• Upper extremity (UE) motor recovery after stroke is influenced by interhemispheric communication.
• The interhemispheric competition model suggests increased transcallosal inhibition (TI) from the contralesional hemisphere impairs recovery.
• This model's validity in the subacute phase is increasingly questioned.

Purpose of the Study:

• To investigate the role of contralesional TI in subacute UE motor recovery following ischemic stroke.
• To determine if abnormally strengthened TI impedes or supports motor function recovery.
• To challenge or confirm the interhemispheric competition model in the subacute recovery period.

Main Methods:

• Longitudinal study of 30 mild-to-moderate stroke subjects over six months.
• Assessed contralesional TI using transcranial magnetic stimulation (TMS) measuring the ipsilateral silent period (iSP).
• Quantitatively and clinically evaluated UE motor functions, including strength, control, individuation, and activity limitation.

Main Results:

• Contralesional TI remained largely static throughout the subacute period.
• No significant relationship was found between TI levels and motor function recovery in the proximal or distal UE.
• Inconsistent associations suggested stronger TI might correlate with less hand impairment and activity limitation.

Conclusions:

• There is no compelling evidence for a maladaptive role of contralesional TI in subacute UE motor recovery.
• Findings challenge the interhemispheric competition model's applicability in the early post-stroke phase.
• Reconsideration of targeting contralesional TI with neuromodulatory strategies in subacute stroke recovery is warranted.