Epidemiologic Overview of Synkinesis in 353 Patients with Longstanding Facial Paralysis under Treatment with Botulinum Toxin for 11 Years

Background: Patients with longstanding facial paralysis often exhibit synkinesis. Few reports describe the prevalence and factors related to the development of synkinesis after facial paralysis. Botulinum toxin type A injection is an important adjunct treatment for facial paralysis-induced asymmetry and synkinesis. The authors assessed the clinical and epidemiologic characteristics of patients with sequelae of facial paralysis treated with botulinum toxin type A injections to evaluate the prevalence of synkinesis and related factors. Methods: A total of 353 patients (age, 4 to 84 years; 245 female patients) with longstanding facial paralysis underwent 2312 botulinum toxin type A injections during an 11-year follow-up. Doses used over the years, previous treatments (electrical stimulation, operations), and how they correlated to postparalysis and postreanimation synkinesis were analyzed. Results: There was a significant association between cause and surgery. Most patients with facial paralysis caused by a congenital defect, trauma, or a tumor underwent reanimation. There were no sex- or synkinesis-related differences in the doses used, but the doses were higher in the reanimation group than in the no-surgery group. Synkinesis was found in 196 patients; 148 (41.9 percent) presented with postparalysis synkinesis (oro-ocular, oculo-oral) and 58 (16.4 percent) presented with postreanimation synkinesis. Ten patients presented with both types. Conclusions: This study determined the high prevalence (55.5 percent) of synkinesis in patients with longstanding facial paralysis. Postparalysis synkinesis was positively associated with infectious and idiopathic causes, electrical stimulation, facial nerve decompression, and no requirement for surgery. Postreanimation synkinesis was present in 28.2 percent of reanimated patients and was significantly associated with microsurgical flaps, transfacial nerve grafting, masseteric-facial anastomosis, and temporalis muscle transfers.