title: Motor unit number index (MUNIX) in the orbicularis oculi muscle of healthy subjects.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Neurology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Republic of Korea.
authors.forename: Suk-Won
authors.initials: SW
authors.lastname: Ahn
authors.forename: Ki-Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Jee-Eun
authors.initials: JE
authors.lastname: Kim
authors.forename: Je-Young
authors.initials: JY
authors.lastname: Shin
authors.forename: Dong-Gun
authors.initials: DG
authors.lastname: Kim
authors.forename: Kwang-Woo
authors.initials: KW
authors.lastname: Lee
authors.forename: Jung-Joon
authors.initials: JJ
authors.lastname: Sung
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005152:Facial Muscles / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D055815:Young Adult
keywords: MUNIX; amyotrophic lateral sclerosis; facial nerve; motor unit; orbicularis oculi muscle