Intracortical and intercortical networks in patients after stroke: a concurrent TMS-EEG study.
Zhongfei Bai, Jack Jiaqi Zhang, Kenneth N K Fong
PMID 37533093WHAT IT FOUND
Chronic stroke patients with mild upper-limb impairment showed reduced excitability in the affected motor cortex and weaker connectivity between that region and frontoparietal areas, measured by brain stimulation and EEG.
The study did not test a treatment, so it offers no basis for changing therapy.
Key findings
01The affected motor cortex had higher resting thresholds and smaller active motor-evoked potentials than the unaffected side, indicating reduced corticospinal excitability.
02The cortical silent period was significantly prolonged on the affected side compared with both the unaffected side and healthy controls.
03Stimulation of the affected motor cortex produced lower connectivity with prefrontal and parietal regions in the theta band and reduced whole-brain network integration.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study did not test any intervention or treatment, so it cannot inform clinical practice decisions. All patients had mild upper-limb impairment (mean Fugl-Meyer score 60.3 out of 66), so findings may not apply to patients with more severe disability. No significant associations were found between the neurophysiological measures and motor function, limiting the clinical interpretability of the findings. The cohort was heterogeneous in lesion location, and the small number of patients with cortical lesions prevented subgroup analysis. A realistic sham TMS condition was not used, so residual auditory or somatosensory artefacts may have influenced the EEG results. The cortical silent period was analysed using a single method with no consensus in the field, limiting comparability with previous studies. Only the primary motor cortex was stimulated, so findings cannot be generalised to other brain regions.
Declared interests
The authors declared no conflicts of interest. The work was funded by the Shanghai Sailing Program, the Shanghai Municipal Health Commission Clinical Research Program, and the Research Grants Council, University Grants Committee.
The easy way to misread this
Do not interpret the reduced connectivity and altered excitability as markers that predict recovery or guide treatment selection. The study found no significant correlation between any neurophysiological measure and motor function, and it tested no intervention, so these findings describe a group average rather than a clinically actionable biomarker.