Laser acupuncture and photobiomodulation therapy in Bell's palsy with a duration of greater than 8 weeks: a randomized controlled trial

Bell's palsy is a condition that causes weakness or paralysis of the facial muscles, usually of sudden onset, and may result from viral infections, autoimmune disease, diabetes, or emotional factors. Although most patients recover naturally, some experience incomplete recovery, especially after 8 weeks from symptom onset. This randomized controlled trial investigated whether laser acupuncture combined with photobiomodulation therapy could improve symptoms in patients with long-duration Bell's palsy. The study was conducted between May 2021 and April 2023 at Beijing Tongren Hospital, including 84 adults aged 18 to 60 years who had facial palsy for more than 8 weeks.

Participants were randomly divided into two groups: the experimental group received 72 sessions of laser acupuncture (3 times per week) using a class IV laser with two synchronized sources (905 nm pulsed at 75 W peak power and 808 nm continuous at 1 W), while the control group received the same procedure but with laser parameters considered ineffective. The treatment protocol included 5 acupuncture points on the affected side of the face (ST-2, ST-4, ST-6, GB-14, GB-20) and 7 points applied bilaterally on the limbs and trunk (LI-4, LI-11, ST-25, ST-36, SP-6, KI-3, LR-3). Each point was stimulated for 1 minute, totaling 19 points per session. Efficacy was measured through clinical scales and objective electrophysiological tests.

The House-Brackmann scale was used to assess overall facial motor function, while the Sunnybrook scale provided a more detailed assessment of facial movements. Electrophysiological tests included electroneurography (ENoG) to measure action potentials of facial muscles, electromyography (EMG) to analyze muscle electrical activity, and blink reflex testing to assess facial nerve function. Results showed significant improvements in the laser acupuncture group. On the House-Brackmann scale, 89% of patients in the laser group showed significant improvement compared with only 24% of the control group.

The Sunnybrook scale showed a mean difference of 20.26 points favoring the laser group. Electrophysiological tests confirmed these clinical improvements: electroneurography showed significant reduction in abnormalities in all muscles tested (orbicularis oculi, frontalis, orbicularis oris, and nasalis), with odds ratios ranging from 0.06 to 0.14, indicating a much lower probability of abnormalities in the laser group. Electromyography demonstrated improvements in amplitude and duration of motor unit action potentials in all assessed muscles. The blink reflex test also showed significant improvements, with reduction in abnormalities of the R1 and R2 components of the reflex.

The clinical implications are important, as this study provides evidence that laser acupuncture can be a viable therapeutic option for patients with chronic Bell's palsy, a population for which few effective treatment options exist. Photobiomodulation therapy, being noninvasive and with few known adverse effects, represents a safe alternative to pharmacological treatments. The proposed mechanism involves anti-inflammatory and neural regeneration effects promoted by laser stimulation. However, the study has some limitations.

It was conducted at a single center, which may limit generalization of the results. Follow-up was limited to the end of treatment, not allowing assessment of long-term durability of benefits. In addition, the study excluded traumatic or iatrogenic facial palsy, limiting its applicability to other causes of facial palsy. Acupuncture point selection was based on clinical experience and traditional Chinese medicine, but the exact mechanism of how stimulating distant points affects facial nerve function is not yet fully elucidated and requires further interdisciplinary research.