Efficacy of photobiomodulation therapy on Bell's palsy symptoms: a systematic review

Bell's palsy, characterized by sudden facial paralysis, affects a significant proportion of the population annually, yet its exact cause remains elusive. Recently, increasing attention has been directed towards photobiomodulation therapy (PBMT) and its prospective contribution to managing various neurological and musculoskeletal conditions, including Bell's palsy. A systematic literature search of different databases was performed using a specific search strategy to find eligible studies that evaluated the potential of PBMT in managing Bell's palsy, considering its non-invasive nature and tissue healing properties. Data extraction was done based on inclusion and exclusion criteria. The systematic review included studies published from 1993 to 2022, examining the effects of photobiomodulation therapy on Bell's palsy. The studies, involving 21 to 120 participants aged 18 to 70, utilized various PBMT parameters such as wavelengths (830-850 nm and 808/905 nm), energy densities (8-20 J/cm²), and irradiation times (10-125 s). The results demonstrated significant improvements in facial muscle function, pain intensity, and muscle strength, showing that PBMT is effective in enhancing facial nerve function recovery in Bell's palsy patients. Statistical analysis showed that PBMT treatments had significant improvements compared to control groups (p < 0.05). Our systematic review indicates that photobiomodulation therapy can improve facial muscle function, pain intensity, and muscle strength in Bell's palsy patients. Notably, wavelengths of 830-850 nm and the combination of 808/905 nm yielded the most favorable results. However, due to heterogeneity in study designs, PBMT parameters, and outcome measures, further standardized and well-designed randomized controlled trials are necessary to establish optimal treatment protocols and validate these findings comprehensively.