Efficacy evaluation of temporomandibular arthroscopic assisted masseter nerve avulsion on hemimasticatory spasm

Hemimasticatory spasm (HMS) is a masticatory muscle disorder without an effective treatment approach at present. This retrospective analysis aims to investigate the clinical efficacy of temporomandibular arthroscope-assisted masseteric nerve avulsion on HMS and thereby further determine a more effective therapeutic strategy for HMS patients.Four patients with HMS receiving temporomandibular arthroscope-assisted masseteric nerve avulsion in the neurology department of oral surgery of our hospital from April 2017 to April 2018 were recruited in this study. Through a clinical follow-up period of 36 months, the comprehensive efficacy of arthroscope-assisted masseteric nerve avulsion was evaluated combined with an electrophysiological electromyogram. Furthermore, the maximum muscle strength and masticatory efficiency of the sound and affected sides were measured to determine whether there were complications. The morphology of the myelin sheath of the masseteric nerve avulsed in the operation was observed under the transmission electron microscope.The 3 years of follow-up showed that complete remission of HMS was seen in 4 patients with the score reduced to grade 0, showing satisfactory clinical efficacy. Electrophysiological electromyogram demonstrated an absence of obvious high-frequency group discharge potential in the 4 patients within 3 years after the operation, and the overall efficacy combined with the clinical efficacy was considered satisfactory. The maximum masseter strength of the sound side had no significant change, but that of the affected side was slightly decreased. The masticatory efficiency of the affected side was slightly decreased immediately after the operation but returned to the preoperative level 1 year after the operation, suggesting that this operation did not affect the masticatory function of the patients. No obvious demyelination was found in the avulsed nervous tissues.Temporomandibular arthroscope-assisted masseteric nerve avulsion yielded satisfactory and stable overall efficacy on the treatment of HMS. The masticatory efficiency of the affected side was optimally preserved, while the maximum masseter muscle strength of the affected side was partially decreased.