Effect of Acupuncture on Functional Connectivity of Anterior Cingulate Cortex for Bell's Palsy Patients with Different Clinical Duration
Wu et al. · Evidence-Based Complementary and Alternative Medicine · 2015
Evidence Level
MODERATEOBJECTIVE
To investigate how acupuncture affects functional connectivity of the anterior cingulate cortex in patients with Bell's palsy at different stages of disease
WHO
28 patients with Bell's palsy and 20 healthy controls
DURATION
Single acupuncture session with neuroimaging analysis
POINTS
Hegu (LI-4) contralateral to the affected side of the face
🔬 Study Design
Early Group
n=18
Paralysis <14 days, acupuncture at LI-4
Late Group
n=21
Paralysis >14 days, acupuncture at LI-4
Recovered Group
n=19
Normal facial function, acupuncture at LI-4
Controls
n=20
Healthy individuals, acupuncture at LI-4
📊 Results in numbers
Connectivity changes - early group
Connectivity changes - late group
Changes in recovered group
Changes in healthy controls
📊 Outcome Comparison
Changes in Functional Connectivity
This study showed that acupuncture affects the brain differently depending on the stage of Bell's palsy. In recent cases, acupuncture decreases certain brain connections, while in later cases it strengthens these connections, suggesting a regulatory role of acupuncture in facial recovery.
Article summary
Plain-language narrative summary
Bell's palsy is a condition that affects the facial nerve, causing weakness or paralysis of one side of the face. Although acupuncture is widely used to treat this condition in many countries, the underlying neurological mechanisms remain poorly understood. This innovative study used functional magnetic resonance imaging to investigate how acupuncture affects functional connectivity of the anterior cingulate cortex (ACC), a brain region important for error processing and performance monitoring. Investigators recruited 48 participants, divided into four groups: patients with Bell's palsy in the early stage (less than 14 days), late stage (more than 14 days), recovered patients, and healthy controls.
All received acupuncture at the Hegu point (LI-4) on the side opposite the facial paralysis. During the procedure, three neuroimaging sessions were performed: before, during, and after acupuncture. Results revealed distinct patterns of brain response depending on disease stage. In the early group, acupuncture caused a significant decrease in functional connectivity between the ACC and motor areas such as the superior and middle frontal gyrus, suggesting a modulatory effect during the acute injury phase.
In contrast, the late group showed increased connectivity between the ACC and regions such as the superior temporal gyrus, insula, and putamen, indicating strengthening of connections during the recovery phase. Interestingly, neither the recovered group nor the healthy controls showed significant changes in connectivity, suggesting that acupuncture acts primarily when there is functional imbalance. These findings support the traditional Chinese medicine theory that acupuncture works by restoring homeostatic balance of the organism. The changes observed in the homeostatic afferent processing network, particularly involving the ACC and insula, indicate that acupuncture may facilitate the cortical reorganization necessary for functional recovery.
The study has several important limitations, including the absence of a no-treatment control group due to ethical considerations, which prevents differentiation between the effects of acupuncture and natural recovery. In addition, the relatively small sample size and the observational nature of the study limit the generalizability of the results.
Strengths
- 1Use of advanced neuroimaging to investigate acupuncture mechanisms
- 2Analysis of different stages of Bell's palsy
- 3Rigorous image-processing methodology
- 4Results consistent with traditional Chinese medicine theory
Limitations
- 1Absence of a no-treatment control group
- 2Small sample size in each subgroup
- 3Inability to distinguish between acupuncture effect and natural recovery
- 4Analysis limited to a single treatment session
Expert Commentary
Dr. Marcus Yu Bin Pai
MD, PhD · Pain Medicine · Physical Medicine and Rehabilitation · Medical Acupuncture
▸ Clinical Relevance
Bell's palsy confronts the clinician with a central tactical decision: when to intervene and with what intensity. This work offers neuroimaging substrate to justify the timing of acupuncture along the clinical course of the disease. The finding that modulation of the anterior cingulate cortex occurs in diametrically opposite directions in early and late phases reinforces the approach that many rehabilitation services already adopt empirically — treat early, but recognize that late treatment also has a relevant, albeit distinct, mechanism of action. For the physiatrist, this translates into practice: patients referred more than 14 days after the onset of paralysis should not be considered outside the therapeutic window. Inclusion of contralateral LI-4 as a standardized intervention also provides a basis for reproducible protocols in facial rehabilitation outpatient settings, integrating acupuncture into the armamentarium of electrical stimulation, neuromuscular exercises, and corticosteroid therapy already established.
▸ Notable Findings
The most intriguing finding of the study is the bidirectionality of the ACC response: reduced connectivity with frontal motor areas in the acute phase and increased connectivity with the insula, putamen, and superior temporal gyrus in the late phase. This suggests that acupuncture does not act through a single, fixed mechanism but rather adapts its action to the functional state of the central nervous system at the moment of stimulation — a behavior that neurophysiology calls state-dependent modulation. Equally notable is the absence of response in the recovered and healthy-control groups, which implies that the central effect of acupuncture depends on the existence of underlying functional imbalance. This pattern is consistent with the concept of afferent homeostasis mediated by the ACC-insula network, and positions acupuncture not as an indiscriminate stimulator but as a regulatory agent sensitive to the patient's neurological context.
▸ From My Experience
In my practice with Bell's palsy, I have observed that patients referred late — frequently 3 to 6 weeks after symptom onset, when corticosteroid therapy has already been completed without full recovery — are those who benefit most from a structured acupuncture protocol combined with facial neuromuscular rehabilitation. I tend to see initial signs of motor response between the third and fifth session, with more consistent functional gain between the eighth and twelfth session. The profile that responds best is the patient with grade III or IV paralysis on the House-Brackmann scale, without established synkinesis. When frank synkinesis is present, I prefer to combine botulinum toxin before resuming the acupuncture cycle. Combination with electromyographic biofeedback is routine in our service. The finding from this article that healthy controls do not exhibit connectivity changes corroborates something I observe clinically: in patients without neurological deficit, the effect of acupuncture at points such as LI-4 is far less expressive in motor terms, which informs candidate selection for treatment.
Full original article
Read the full scientific study
Evidence-Based Complementary and Alternative Medicine · 2015
DOI: 10.1155/2015/646872
Access original articleScientific Review
Marcus Yu Bin Pai, MD, PhD
CRM-SP: 158074 | RQE: 65523 · 65524 · 655241
PhD in Health Sciences, University of São Paulo. Board-certified in Pain Medicine, Physical Medicine and Rehabilitation, and Medical Acupuncture. Scientific review and curation of every entry in this library.
Learn more about the author →Medical disclaimer: This content is for educational purposes only and does not replace consultation, diagnosis, or treatment by a qualified professional. Some information may be assisted by artificial intelligence and is subject to inaccuracies. Always consult a physician.
Content reviewed by the medical team at CEIMEC — Integrated Centre for Chinese Medicine Studies, a reference in Medical Acupuncture for over 30 years.
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