Endoscope-Assisted Avulsion of the Masseter Nerve Attached to the Temporomandibular Joint Disc for the Treatment of Hemimasticatory Spasm: A Report of Two Cases.

[OBJECTIVE] Hemimasticatory spasm (HMS) is a rare masticatory muscle disorder. Drug therapy, microvascular decompression, and botulinum toxin have had varying efficacy and adverse effects. We have reported the cases of 2 patients who had undergone a novel therapy for HMS, based on endoscope-assisted nerve avulsion of the masseter nerve attached to the temporomandibular joint (TMJ) disc.

[METHODS] We performed a retrospective study of 2 patients with HMS who had undergone surgery from June 2014 to June 2017 at the oral surgery department of Shanghai Ninth People's Hospital affiliated to Shanghai JiaoTong University School of Medicine. Both patients had undergone endoscope-assisted avulsion of the masseter nerve attached to the TMJ disc. Both patients were evaluated by electromyography postoperatively and were followed up for 36 months after surgery.

[RESULTS] Both patients had had all the signs and symptoms of HMS. The HMS had resolved immediately after surgery. At 1 week after surgery, electromyography revealed that the high-frequency group discharge potential in the motor unit accompanying the spasm was no longer present, and the effect was maintained for the 36-month follow-up period. These results indicated a good curative effect. Electromyography also showed strength weakness and mild shape atrophy of the masseter muscle on the affected side.

[CONCLUSIONS] Endoscope-assisted avulsion of the masseter nerve attached to the TMJ disc showed a good curative effect, little trauma, few complications, and a quick postoperative recovery. It could be used as an alternative treatment of HMS for selected patients.