Impacts of repetitive transcranial magnetic stimulation parameters on cerebral hemodynamics in patients with disorders of consciousness

Significance Repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising noninvasive neuromodulation technique for patients with disorders of consciousness (DOC). However, the specific effects of rTMS stimulation parameters on this population remain insufficiently characterized. Objectives Functional near-infrared spectroscopy (fNIRS) was used to evaluate the real-time and short-term effects of rTMS with different stimulation parameters on patients with DOC. Methods The hemodynamic data were acquired from 20 patients with DOC during rTMS at different frequencies (10 Hz and 20 Hz) and different target sites (at F3 and F4), yielding four experimental conditions. The spatiotemporal characteristics of hemodynamics across these conditions were quantitatively compared to investigate the real-time and short-term after-effects of rTMS. Results Results showed that the hemodynamic responses significantly increased following the high- frequency (both 10 Hz and 20 Hz) rTMS. With a fixed total number of stimulation pulses, the lower-frequency, longer-duration protocol (10 Hz, 10 s) produced stronger hemodynamic responses than the higher-frequency, shorter-duration protocol (20 Hz, 5 s) across measured brain areas. Notably, rTMS applied to either the left (F3) or right (F4) DLPFC evoked significantly stronger ipsilateral than contralateral hemodynamic responses, indicating a lateralized neuromodulation effect. Conclusion The fNIRS-based monitoring offers a valuable method for evaluating the neuromodulation efficacy of rTMS, providing a novel perspective for optimizing neuromodulation parameters for patients with DOC.