Motor unit number index (MUNIX) in the orbicularis oculi muscle of healthy subjects

• Published in: Muscle & nerve Vol. 51; no. 2; pp. 197 - 200
• Main Authors: Ahn, Suk-Won, Kim, Ki-Won, Kim, Jee-Eun, Shin, Je-Young, Kim, Dong-Gun, Lee, Kwang-Woo, Sung, Jung-Joon
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.02.2015; Wiley Subscription Services, Inc
• Subjects: Action Potentials - physiology; Adult; amyotrophic lateral sclerosis; Electric Stimulation; Electromyography; Facial Muscles - physiology; facial nerve; Female; Healthy Volunteers; Humans; Male; Motor Neurons - physiology; motor unit; MUNIX; Muscle Contraction - physiology; orbicularis oculi muscle; Young Adult; motor unit; MUNIX; facial nerve; amyotrophic lateral sclerosis; orbicularis oculi muscle
• ISSN: 0148-639X; 1097-4598; 1097-4598
• DOI: 10.1002/mus.24292

ABSTRACT Introduction: The motor unit number index (MUNIX) refers to an electrophysiological method that measures the number of motor units in the surface electromyographic interference pattern (SIP) recorded during graded muscle contractions. MUNIX studies of limb muscles have been conducted, but MUNIX studies of bulbo‐facial muscles have not been reported. Methods: We assessed bilateral orbicularis oculi muscles using MUNIX, and the reference values and reproducibility of MUNIX and motor unit size index (MUSIX) were investigated in healthy subjects. Results: In this study, MUNIX was applied successfully to the orbicularis oculi muscles and showed good reproducibility. The correlation coefficients for MUNIX and MUSIX were 0.803 and 0.592, respectively, and the coefficients of variation were 20.9% and 8.5%, respectively. Conclusions: The MUNIX procedure for the orbicularis oculi muscle would be a useful tool for evaluating bulbar symptoms, especially in amyotrophic lateral sclerosis. Muscle Nerve 51: 197–200, 2015