Association of TMS-EEG interhemispheric imbalance with upper limb motor impairment in chronic stroke patients: An exploratory study

Objective: We aimed to investigate the involvement of interhemispheric cortical dynamics as measured by combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) in recovery of upper limb (UL) motor functions in chronic stroke patients. Methods: Ten patients with a history of single ischemic chronic stroke were enrolled (4F, 63.8 ± 9.9 years). Each patient underwent TMS-EEG recordings to evaluate interhemispheric cortical dynamics as well as a reaching task recorded with inertial measurement units, and a series of clinical assessments. TMS-EEG neurophysiological data were analysed considering spatiotemporal, power response, and interhemispheric balance (IHB) dynamics. Results: We found that IHB index (IHBi) and low-frequency power (LFP) (4–13 Hz) in the affected hemisphere were associated with the degree of UL impairment. Conclusion: Increased IHBi due to stroke is an unfavourable factor of UL’ functions. Similarly, LFP of both hemispheres is strongly correlated with clinical and kinematic outcomes. Significance: TMS-EEG biomarkers of interhemispheric unbalance could be used to estimate functional recovery and drive tailored neuromodulation and neurorehabilitation approaches.