Ann Rehabil Med.  2013 Jun;37(3):433-437. 10.5535/arm.2013.37.3.433.

Diagnosis of Zygomaticus Muscle Paralysis Using Needle Electromyography With Ultrasonography

• Yoo SH
• Kwon HK
• Lee SH
• Lee SJ
• Ha KW
• Yun HS

• KMID: 2219543
• DOI: http://doi.org/10.5535/arm.2013.37.3.433

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.

Keyword

Ultrasonography-guided; Zygomaticus; Needle electromyography

MeSH Terms

Electromyography
Facial Asymmetry
Facial Muscles
Facial Nerve
Female
Humans
Masseter Muscle
Mouth
Muscles
Needles
Neural Conduction
Paralysis
Physical Examination
Smiling
Volition

Figure

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  Fig. 1 Clinical figures of face. (A) Resting state, (B) frontalis muscle activation, and (C) orbicularis oris muscle activation demonstrated symmetry on both sides. However, (D) zygomaticus muscle activation (on smiling) showed asymmetry.

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  Fig. 2 Ultrasonographic figures of zygomaticus muscle. (A) Left zygomaticus muscle longitudinal view, (B) left zygomaticus muscle crossection view, (C) right zygomaticus muscle longitudinal view, (D) right zygomaticus muscle crossection view thickness and area of bilateral muscles were symmetric. Red arrow, zygomaticus muscle; Z, zygomatic bone.

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  Fig. 3 Positive sharp waves and motor unit action potentials (MUAP) of zygomaticus muscle. (A) Needle insertion position in the muscle, (B) positive sharp waves in left zygomaticus, (C) MUAPs in left zygomaticus, and (D) MUAPs in right zygomaticus: gain, 200 µV/div; sweep speed, 10 ms/div. Green arrow, needle electrode; red arrow, zygomaticus muscle.

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