High-frequency rTMS over the left ventrolateral prefrontal cortex ameliorates gastrointestinal injury in patients with stroke: an fNIRS-HRV study

Autonomic dysfunction resulting from damage to the central autonomic network is a common complication of acquired brain injury (ABI). The prefrontal and insular cortices regulate visceromotor autonomic functions, and gastrointestinal dysfunction following ABI may involve impaired autonomic innervation. While repetitive transcranial magnetic stimulation (rTMS) shows potential for studying the top-down control of visceral processes, the mechanisms linking disrupted functional connectivity to autonomic dysfunction and the restorative effects of neuromodulation remain unclear. Sixty-four ABI patients with acute gastrointestinal injury (AGI) were randomized into a control group (CG, n = 32) and an rTMS group (TG, n = 32). Both groups received standard rehabilitation, while the TG additionally underwent 10 Hz rTMS over the left ventrolateral prefrontal cortex (VLPFC-L) (five sessions per week for two weeks). Autonomic function was assessed via heart rate variability (HRV), and whole-brain functional connectivity was measured using 106-channel functional near-infrared spectroscopy (fNIRS). Graph-theoretical network metrics were analyzed. Compared to the CG, the TG showed reduced acute gastrointestinal injury scores, decreased low-frequency (LF) power, a lower low-frequency to high-frequency (LF/HF) ratio, and increased high-frequency (HF) power. Functional connectivity increased in the left ventrolateral prefrontal cortex (VLPFC-L), particularly with the right frontal pole, bilateral premotor cortices, and the left pre-motor/supplementary motor cortex. Global and local network efficiency also improved. These findings indicate that VLPFC-L-targeted rTMS can restore neuroautonomic integration and gastrointestinal function in ABI patients. This study demonstrates the potential of fNIRS and HRV as complementary tools for assessing the effects of neuromodulation on autonomic circuits.