• Lina Daghsen, Thomas Checkouri, Aymric Wittwer, Romain Valabregue, Damien Galanaud, François-Xavier Lejeune, Mohammed Doulazmi, Jean-Charles Lamy, Pierre Pouget, Emmanuel Roze, and Charlotte Rosso.
• Institut du Cerveau, ICM, Inserm U1127, CNRS UMR 7225, Sorbonne Université, Paris 75013, France.
• J. Neurol. Neurosurg. Psychiatr. 2024 Dec 16; 96 (1): 859485-94.

BackgroundEvaluation of the structural integrity and functional excitability of the corticospinal tract (CST) is likely to be important in predicting motor recovery after stroke. Previous reports are inconsistent regarding a possible link between CST structure and CST function in this setting. This study aims to investigate the structure‒function relationship of the CST at the acute phase of stroke (<7 days).MethodsWe enrolled 70 patients who had an acute ischaemic stroke with unilateral upper extremity (UE) weakness. They underwent a multimodal assessment including clinical severity (UE Fugl Meyer at day 7 and 3 months), MRI to evaluate the CST lesion load and transcranial magnetic stimulation to measure the maximum amplitude of motor evoked potential (MEP).ResultsA cross-sectional lesion load above 87% predicted the absence of MEPs with an accuracy of 80.4%. In MEP-positive patients, the CST structure/function relationship was bimodal with a switch from a linear relationship (rho=-0.600, 95% CI -0.873; -0.039, p<0.03) for small MEP amplitudes (<0.703 mV) to a non-linear relationship for higher MEP amplitudes (p=0.72). In MEP-positive patients, recovery correlated with initial severity. In patients with a positive MEP <0.703 mV but not in patients with an MEP ≥0.703 mV, MEP amplitude was an additional independent predictor of recovery. In MEP-negative patients, we failed to identify any factor predicting recovery.ConclusionThis large multimodal study on the structure/function of the CST and stroke recovery proposes a paradigm change for the MEP-positive patients phenotypes and refines the nature of the link between structural integrity and neurophysiological function, with implications for study design and prognostic information.© Author(s) (or their employer(s)) 2025. No commercial re-use. See rights and permissions. Published by BMJ Group.

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