Evaluation of the integrity of the facial muscles in leprosy patients using surface electromyography: a cross-sectional study

Objective This study sought to evaluate facial muscle integrity in clinical forms of leprosy through surface electromyography. Methods For evaluation of facial muscle integrity, 19 healthy subjects and 71 patients diagnosed with leprosy and under treatment in a National leprosy reference center were recruited. The muscles investigated, through surface electromyography, were the frontalis, orbicularis oculi, zygomaticus, masseter, and orbicularis oris. The evaluated features were Root Mean Square (RMS) and Mean frequency (Fmean). The facial muscles were analyzed jointly and separately for each leprosy clinical form and healthy individuals. Results Regarding the Fmean, there was a difference noted between the values of healthy subjects and patients of all clinical forms, except for the LL form (p = 0.986). The highest frequency values were seen in TT and BL forms, which did not present a significant difference between each other (p = 0.757). Asymmetry of the facial muscles was detected in TT (RMS) and TT, BB, and LL forms from the Fmean. RMS and Fmean indicated motor neurogenic impairment in facial muscles of all leprosy patients, except the LL form. Conclusions Surface electromyography is shown to be an auxiliary tool for the diagnosis of facial motor disorders imperceptible to clinical examination, helping to prevent impairments, which is fundamental for the social inclusion of leprosy patients.