Distinct Disconnection Patterns Explain Task-Specific Motor Impairment and Outcome After Stroke

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Abstract
BACKGROUND: Stroke is increasingly understood as a network disorder with symptoms often arising from disruption of white matter connectivity. Previous connectome-based lesion-symptom mapping studies revealed that poststroke motor deficits are not only associated with damage to the core sensorimotor network but also with nonsensorimotor connections. However, whether task-specific initial impairment and outcome are based on distinct disconnection patterns remains unknown. METHODS: To address this question, we included lesion information and assessments of distinct aspects of upper limb motor impairment of 113 patients with early subacute stroke (mean age, 65.95 years). We used connectome-based lesion-symptom mapping, based on a normative structural connectome, and a machine learning algorithm to predict individual levels of task-specific motor impairment and outcome >3 months later. RESULTS: We identified task-specific disconnection patterns that significantly predicted initial motor impairment and outcome and a task-general reach-to-grasp network including both sensorimotor and nonsensorimotor areas. More complex reach-to-grasp movements showed a substantial overlap in disconnections for the prediction of impairment and outcome. Conversely, disconnections indicative of more basal aspects of motor control substantially differed between the prediction of initial impairment and outcome at the chronic stage poststroke. Similarly, the significance of interhemispheric disconnections changed in a task- and time-dependent fashion. CONCLUSIONS: In summary, our study identified distinct disconnection patterns indicative of specific aspects of motor impairment and outcome after stroke, highlighting a time- and task-dependent role of the contralesional hemisphere and suggesting a domain-general compensatory role of nonsensorimotor temporal areas. From a mechanistic perspective, differences in disconnection patterns predictive of initial motor impairment versus outcome suggest a stronger dependence of basal motor control on the brain’s structural reserve during motor recovery. Our results extend our current network-level understanding of task-specific motor impairment and recovery, and emphasize the potential of connectome-based lesion-symptom mapping for future clinical applications.

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