Exploring the potential central regulatory mechanisms of acupuncture for acute-stage Bell's palsy: an fMRI-based investigation

Bell's palsy is a condition that causes sudden weakness or paralysis on one side of the face due to inflammation of the facial nerve. Although many patients recover naturally, the process can be slow and some are left with permanent sequelae. Acupuncture has shown efficacy in the treatment of this condition, but the mechanisms by which it acts on the central nervous system were not well understood. This pioneering study used functional magnetic resonance imaging to investigate how acupuncture influences brain activity in patients with acute Bell's palsy.

Researchers followed 55 patients with early-stage Bell's palsy (1-7 days after symptom onset) and 48 healthy controls. Acupuncture treatment was applied at specific points on the affected face and hands, including Qianzheng, Yifeng, Sibai, Yangbai, Yuyao, Quanliao, Jiache, Dicang, Touwei, and Hegu bilateral. Each session lasted 30 minutes, with a frequency of three times per week for 28 days. The methodology included clinical assessments through the House-Brackmann, Sunnybrook, and Facial Disability Index scales, in addition to functional magnetic resonance imaging examinations before and after treatment.

Resting-state fMRI allowed analysis of spontaneous brain activity through two indicators: fALFF (fractional amplitude of low-frequency fluctuations) and ReHo (regional homogeneity), which measure, respectively, the intensity of local neuronal activity and synchronization between adjacent brain areas. Clinical results were impressive, with an efficacy rate of 96.4%. Of the 55 patients, 27 were considered cured, 23 showed significant improvement, 3 showed improvement, and only 2 did not respond to treatment. There were statistically significant improvements on all clinical assessment scales.

More importantly, the study revealed specific changes in brain activity that accompanied clinical recovery. Before treatment, patients with Bell's palsy showed abnormal activity patterns in several brain regions compared with healthy controls. Notably, there was increased activity in the postcentral gyrus (sensory area) and middle frontal gyrus (motor area), suggesting a compensatory effort by the brain to cope with facial dysfunction. After acupuncture treatment, examinations showed significant functional reorganization in brain areas related to sensation, movement, and emotion.

The precentral gyrus (primary motor cortex) showed increased activity, indicating improved facial motor control capacity. Simultaneously, there was reduced activity in the superior frontal gyrus, a region associated with emotional regulation, suggesting that acupuncture also alleviated the psychological stress caused by altered facial appearance. Changes in the thalamus and temporal areas indicated improvement in sensory integration and information processing. The study also revealed that even after clinical recovery, some patients maintained brain functional reorganization, suggesting lasting neuroplastic adaptations.

This finding is important as it indicates that the brain develops new functional strategies that may protect against future recurrences. Researchers propose that acupuncture facilitates neuroplasticity — the brain's capacity to form new connections and reorganize neural circuits. This occurs through stimulation of areas such as the primary sensory cortex, motor cortex, and prefrontal cortex, improving connectivity between brain regions responsible for facial control. Limitations of the study include the absence of a sham acupuncture control group, relatively small sample size, and follow-up limited to 28 days.

Future studies should include more rigorous controls and long-term follow-up to confirm the durability of effects. This work provides objective scientific evidence that acupuncture not only treats the symptoms of Bell's palsy but also promotes beneficial neuroplastic changes in the brain. The findings support the use of acupuncture as an evidence-based therapy for acute facial palsy and open avenues for research on the neurobiological mechanisms of traditional Chinese therapies.