Acupuncture alters cortical and corticomuscular functional connectivity in stroke patients with motor dysfunction

This experimental study investigated how acupuncture affects neural connections in stroke patients with motor impairment. Stroke is one of the leading causes of death and disability worldwide, often resulting in severe motor dysfunction that significantly impacts patients' quality of life. Although acupuncture has shown benefits in stroke rehabilitation, the neural mechanisms by which it facilitates motor recovery remain incompletely understood. The researchers recruited 15 patients with ischemic stroke from a Chinese hospital, with a mean age of 65.2 years.

Each patient took part in five experimental sessions: no acupuncture (control), acupuncture at the GV-26 point (Shuigou, located in the philtrum), PC-6 (Neiguan, on the wrist), SP-6 (Sanyinjiao, on the leg), and a condition with all three points simultaneously. The order of sessions was randomized for each participant. During each session, the researchers recorded brain electrical activity using electroencephalography (EEG) and muscle activity using electromyography (EMG) of muscles in the leg affected by the stroke. Participants performed an ankle dorsiflexion task (lifting the foot) while signals were recorded.

The researchers analyzed two main aspects: cerebral functional connectivity (how different brain regions communicate) and corticomuscular coherence (how the brain controls the muscles). To assess brain connectivity, they constructed functional networks and calculated parameters such as clustering coefficient, global efficiency, and nodal degree. For corticomuscular coherence, they measured the synchrony between EEG and EMG signals in different frequency bands. The results revealed specific effects of the different acupuncture points.

In the theta band (4-7 Hz), acupuncture at PC-6 and at the three points simultaneously significantly improved brain-network parameters compared with control. The clustering coefficient increased significantly with the three points (p = 0.012), while global efficiency and nodal degree improved with both PC-6 and the three points. Interestingly, GV-26 alone did not show significant effects on brain connectivity. With regard to corticomuscular coherence, PC-6 and SP-6 were more effective.

In the beta (14-30 Hz) and gamma (32-45 Hz) bands, acupuncture at these points significantly increased coherence between the motor cortex and the leg muscles, indicating better neural control of the muscles. GV-26 again showed minimal effects on this measure. The clinical implications of these findings are important. The study demonstrates that acupuncture can acutely modulate both central and peripheral neural pathways, with specific effects depending on the point used.

PC-6 was particularly effective at improving cerebral functional connectivity, possibly because it was the only point stimulated bilaterally, modulating cortical excitability in both hemispheres. This may reduce excessive interhemispheric inhibition that is common after stroke. PC-6 and SP-6 were superior for strengthening brain-muscle connections, suggesting that different points act at different levels of the motor neural pathways. These results provide preliminary neurobiological evidence for the specificity of acupuncture points and highlight the potential to develop personalized acupuncture prescriptions.

However, the study has important limitations. The sample size was small (15 patients) and only acute effects were assessed. It is not known whether these immediate neurophysiological changes translate into sustained functional improvement. In addition, no sham acupuncture control group was included, which could strengthen the conclusions about the specificity of the effects.

Future studies need to verify whether these acute effects can be maintained and translated into durable motor recovery through long-term randomized clinical trials with larger samples.