The relationship between corticospinal excitability and structural integrity in stroke patients

Area of Science:

• Neuroscience
• Neurology
• Rehabilitation Medicine

Background:

• Predicting motor recovery after stroke is crucial for patient management.
• The corticospinal tract (CST) is vital for motor function, but its structure-function relationship in acute stroke remains unclear.
• Previous studies show inconsistent findings regarding CST integrity and functional recovery post-stroke.

Purpose of the Study:

• To investigate the structure-function relationship of the CST in the acute phase of stroke (<7 days).
• To explore the predictive value of CST integrity and excitability for upper extremity motor recovery.

Main Methods:

• Seventy acute ischemic stroke patients with unilateral upper extremity weakness were enrolled.
• Multimodal assessment included clinical severity (UE Fugl Meyer), CST lesion load via MRI, and motor evoked potential (MEP) amplitude via transcranial magnetic stimulation.
• Data were analyzed cross-sectionally and longitudinally to assess recovery at 3 months.

Main Results:

• A CST lesion load exceeding 87% accurately predicted the absence of MEPs (80.4% accuracy).
• In MEP-positive patients, a bimodal CST structure-function relationship was observed: linear for small MEP amplitudes (<0.703 mV) and non-linear for larger amplitudes.
• MEP amplitude independently predicted recovery in patients with MEPs <0.703 mV, but not in those with MEPs ≥0.703 mV. No predictors were identified for MEP-negative patients.

Conclusions:

• This study proposes a paradigm shift in understanding MEP-positive stroke phenotypes.
• It refines the link between CST structural integrity and neurophysiological function in acute stroke.
• Findings have implications for designing future stroke recovery studies and improving prognostic accuracy.