Cortical connectivity abnormalities assessed by TMS-EEG in patients after a transient ischemic attack

Abstract

Non-motor symptoms following transient ischaemic attack (TIA) may reflect disruption of cortical GABA-dependent functional connectivity. In this case series, we quantified global cortical dynamics using the perturbational complexity index based on state transitions (PCIst) and intertrial coherence (ITC) derived from transcranial magnetic stimulation-electroencephalography (TMS-EEG). Seven patients who presented with sensory, visual, or motor symptoms during TIA underwent TMS-EEG stimulation of the left primary motor cortex. Individual PCIst and ITC values were classified relative to a normative dataset of 164 healthy participants. Six of seven patients exhibited abnormal PCIst and/or ITC values, with alterations most frequently observed in the beta and alpha frequency bands. Four patients reported persistent post-TIA symptoms, including fatigue, memory difficulties, or impaired concentration. These findings suggest that TIA may be associated with measurable alterations in cortical synchronization, and large-scale brain dynamics. Importantly, it is currently unknown whether the observed alterations preceded the TIA, emerged as its consequence, or were influenced by unmeasured mediators such as premorbid factors such as cognitive or affective symptoms. These preliminary findings support further investigation of TMS-EEG-derived measures as candidate neurophysiological biomarkers of cortical network vulnerability or susceptibility to persistent neuropsychiatric symptoms after TIA.