Reduction of sleep-like perilesional slow waves and clinical evolution after stroke: A TMS-EEG study

Objective: Recent studies indicate that brain injuries often lead to the occurrence of sleep-like slow waves in perilesional cortical areas. These slow waves may disrupt local cortico-cortical interactions and contribute to behavioral impairments but are, in principle, reversible. This study employs Transcranial Magnetic Stimulation (TMS) combined with Electroencephalography (EEG) to monitor changes in perilesional slow waves and local cortical interactions examining their relation to changes in stroke severity. Methods: Twelve patients with post-acute/chronic unilateral ischemic cortical stroke participated in a longitudinal study with two assessment points. Each assessment included a neurological evaluation using the National Institutes of Health Stroke Scale (NIHSS) and TMS-EEG recordings targeting perilesional cortical areas. Neurophysiological parameters, such as slow wave amplitude (SWa), high-frequency power (HFp) suppression, and the Perturbational Complexity Index-state transition (PCIst), were extracted from the perilesional EEG responses to TMS to quantify local sleep-like slow waves and cortical interactions. Results: We observed a perilesional reduction in sleep-like slow waves and a restoration of local cortical interactions. Notably, these changes significantly correlated with patients' clinical evolution as assessed by the NIHSS score. Conclusions: These findings highlight the potential of TMS-EEG as an objective tool for tracking neurological evolution post-stroke. Significance: Targeting sleep-like cortical dynamics may be relevant for devising post-stroke rehabilitation strategies.