Diagnosis of Zygomaticus Muscle Paralysis Using Needle Electromyography With Ultrasonography
A 22-year-old woman visited our clinic complaining of left facial palsy that for four weeks. Five weeks earlier, the patient received radiofrequency volumetric reduction for masseter muscles in the bilateral buccal regions at a local medical clinic. Under local anesthesia, monopolar radiofrequency probes were inserted into the lower third of the masseter muscles through oral mucosa and coagulation was done at 20 to 30 spots in each masseter muscle. Her primary symptom was asymmetry of facial muscles. In physical examination, she was freely able to wrinkle the forehead, close the eyes completely, lift the nasal ala up and forward and contract the mouth. The only abnormal finding of the facial expression was an incomplete elevation of the left corner of the mouth when smiling ().\nElectrophysiologic tests such as NCS, EMG, and blink reflex study for evaluation of facial nerve function revealed normal findings. Ultrasonographic search on the affected side around the inferior region of the zygomatic bone revealed a hypomobile tiny zygomaticus muscle (). On the other side, the zygomaticus muscle was drawn upward and laterally and normal muscle activity when the patient was smiling. Thickness and sizes of bilateral muscles were symmetric with the thickness, 0.15 cm/left, 0.18 cm/right and area, 0.18 cm2/left, 0.14 cm2/right.\nEMG needle was inserted under the guidance of ultrasonography into the zygomaticus muscle which led to the detection of abnormal spontaneous activities at rest and small amplitude motor unit action potentials with reduced recruitment patterns on volition ().\nFurthermore, facial magnetic resonance imaging (MRI) was performed to detect muscle atrophy and discontinuity of focal facial nerve branch. However, there was no definite muscle atrophic change or nerve injury lesion such as swelling, fluid collection or mass.