The effects of acupuncture treatment on the right frontoparietal network in migraine without aura patients

Migraine is a neurological disorder that affects more than 100 million people in Europe and the United States, representing one of the 20 most disabling medical conditions globally. Previous functional MRI (fMRI) studies have confirmed multiple functional and structural abnormalities in the resting-state brain networks of migraine patients, especially in the right frontoparietal network (RFPN), which is strongly related to pain processing and regulation. Despite the proven clinical efficacy of acupuncture for migraine, few studies have investigated the neural responses to acupuncture treatment in these patients.

This prospective study used functional neuroimaging to examine the effects of 4 weeks of standard acupuncture treatment on the RFPN of 12 patients with migraine without aura, compared with 12 matched healthy controls. Patients underwent functional MRI before and after treatment, while controls underwent only a single imaging session. The acupuncture protocol followed established Chinese guidelines, using specific bilateral points: Sizhukong, Shuaigu, Fengchi, Taiyang, Hegu, Taichong, Waiguan, Yanglingquan, and Zulinqi. Sessions lasted 30 minutes each, performed five times per week for four consecutive weeks.

The neuroimaging methodology employed independent component analysis and functional connectivity techniques to map intrinsic brain activity. In addition, diffusion tensor imaging (DTI) analyses were performed to detect responses related to nerve fibers. The researchers focused specifically on changes in functional connectivity in the RFPN, a brain network that is dominant in pain processing and includes frontoparietal regions crucial for perception, somesthesia, and nociceptive regulation.

The results showed significant changes in both clinical symptoms and brain activity. Clinically, patients showed substantial reduction in pain intensity (VAS scale from 5.5 to 2.7), decreased attack frequency (from 4.5 to 1.9 episodes per month), and reduced episode duration (from 6.1 to 4.3 days per month). All these improvements were statistically significant (P < 0.05).

Neuroimaging analyses revealed fascinating findings about the underlying neural mechanisms. Before treatment, migraine patients showed significantly decreased functional connectivity in the RFPN, specifically in the left precentral gyrus, left supramarginal gyrus, left inferior parietal lobule, and left postcentral gyrus — all regions closely involved in pain processing. Crucially, this decreased functional connectivity was negatively correlated with patients' pain scores, suggesting that greater pain intensity was associated with greater disconnectivity in these brain networks.

After acupuncture treatment, significant reversal of these abnormalities was observed. Functional connectivity increased significantly in the left precentral gyrus, left inferior parietal lobule, and left postcentral gyrus. Importantly, these changes in brain connectivity were negatively correlated with the decrease in pain scores, indicating that normalization of brain function paralleled clinical improvement.

The DTI analyses provided additional anatomical insights, revealing thalamic radiation fibers connecting the left thalamus to the identified regions of interest. These fibers passed through the internal capsule and external capsule, structures known to be involved in sensorimotor pathways, particularly those related to sensory processing of the head and face.

The clinical implications are significant. This study provides the first neuroimaging evidence that acupuncture can normalize specific abnormalities in brain connectivity in migraine patients. The RFPN, being a network crucial for attention, cognitive processing, and pain regulation, appears to be an important therapeutic target. The correlation between improvements in brain connectivity and symptom reduction suggests that these neural changes may serve as objective biomarkers of treatment response.

However, the study has important limitations that must be considered. The small sample size (12 patients) limits the generalizability of the findings. The absence of a placebo control group prevents determination of whether the observed changes are specific to acupuncture or related to the natural course of the disease. In addition, the DTI data showed only the presence of the fibers, but not quantitative differences in their properties between patients and controls.

In conclusion, this pioneering study demonstrates that acupuncture can induce normalizing effects on the decreased functional connectivity of the RFPN in patients with migraine without aura. The findings suggest potential functional pathways for treatment evaluation and provide insights into the neural mechanisms related to treatment. Future studies with larger samples and controlled designs are still needed to confirm these results and fully elucidate the complex neural mechanisms of acupuncture in migraine treatment.