Mean motor disconnectivity (MMD), evaluated on MRI imaging, explains additional variability in skilled hand function after subacute stroke, beyond motor evoked potential status and corticospinal tract lesion load.

BACKGROUND: Persistent compromised hand function is one of the most common long-term deficits after stroke. It is related to dysfunction of the primary motor cortex (M1) and corticospinal tract (CST) as assessed by magnetic resonance imaging-derived estimates of CST lesion load or by transcranial magnetic stimulation-derived measures, such as motor evoked potential (MEP) status. However, substantial interindividual variability remains with these measures. We tested whether a novel measure, mean motor disconnectivity (MMD), explains additional variation in the hand function of subacute stroke patients. METHODS: Thirty-two participants (15 M/17 F; age, 58.6±9.65 years) after unilateral ischemic stroke involving the CST and related upper extremity weakness were studied within 4 weeks of stroke in a cross-sectional study design at Emory University between 2015 and 2021.