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

Suk Won Ahn, Ki Won Kim, Jee Eun Kim, Je Young Shin, Dong Gun Kim, Kwang Woo Lee, Jung Joon Sung

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


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.

Original languageEnglish
Pages (from-to)197-200
Number of pages4
JournalMuscle and Nerve
Issue number2
StatePublished - 1 Feb 2015

Bibliographical note

Publisher Copyright:
© 2014 Wiley Periodicals, Inc.


  • Amyotrophic lateral sclerosis
  • Facial nerve
  • Motor unit
  • Orbicularis oculi muscle


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