title: Diagnosis of zygomaticus muscle paralysis using needle electromyography with ultrasonography.
abstract: A 22-year-old woman visited our clinic with a history of radiofrequency volumetric reduction for bilateral masseter muscles at a local medical clinic. Six days after the radiofrequency procedure, she noticed a facial asymmetry during smiling. Physical examination revealed immobility of the mouth drawing upward and laterally on the left. Routine nerve conduction studies and needle electromyography (EMG) in facial muscles did not suggest electrodiagnostic abnormalities. We assumed that the cause of facial asymmetry could be due to an injury of zygomaticus muscles, however, since defining the muscles through surface anatomy was difficult and it was not possible to identify the muscles with conventional electromyographic methods. Sono-guided needle EMG for zygomaticus muscle revealed spontaneous activities at rest and small amplitude motor unit potentials with reduced recruitment patterns on volition. Sono-guided needle EMG may be an optimal approach in focal facial nerve branch injury for the specific localization of the injury lesion.
authors.affiliation: Department of Rehabilitation Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Seung Han
authors.initials: SH
authors.lastname: Yoo
authors.forename: Hee Kyu
authors.initials: HK
authors.lastname: Kwon
authors.forename: Sang Heon
authors.initials: SH
authors.lastname: Lee
authors.forename: Seok Jun
authors.initials: SJ
authors.lastname: Lee
authors.forename: Kang Wook
authors.initials: KW
authors.lastname: Ha
authors.forename: Hyeong Suk
authors.initials: HS
authors.lastname: Yun
keywords: Needle electromyography; Ultrasonography-guided; Zygomaticus