Compound muscle action potential and motor function in children with spinal muscular atrophy

Aga Lewelt*, Kristin J. Krosschell, Charles Scott, Ai Sakonju, John T. Kissel, Thomas O. Crawford, Gyula Acsadi, Guy D'Anjou, Bakri Elsheikh, Sandra P. Reyna, Mary K. Schroth, Jo Anne Maczulski, Gregory J. Stoddard, Elie Elovic, Kathryn J. Swoboda

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

88 Scopus citations


Reliable outcome measures that reflect the underlying disease process and correlate with motor function in children with SMA are needed for clinical trials. Maximum ulnar compound muscle action potential (CMAP) data were collected at two visits over a 4-6-week period in children with SMA types II and III, 2-17 years of age, at four academic centers. Primary functional outcome measures included the Modified Hammersmith Functional Motor Scale (MHFMS) and MHFMS-Extend. CMAP negative peak amplitude and area showed excellent discrimination between the ambulatory and non-ambulatory SMA cohorts (ROC = 0.88). CMAP had excellent test-retest reliability (ICC = 0.96-0.97, n = 64) and moderate to strong correlation with the MHFMS and MHFMS-Extend (r = 0.61-0.73, n = 68, P < 0.001). Maximum ulnar CMAP amplitude and area is a feasible, valid, and reliable outcome measure for use in pediatric multicenter clinical trials in SMA. CMAP correlates well with motor function and has potential value as a relevant surrogate for disease status.

Original languageEnglish (US)
Pages (from-to)703-708
Number of pages6
JournalMuscle and Nerve
Issue number5
StatePublished - Nov 2010


  • Compound muscle action potential
  • Motor function
  • Outcome measures
  • Pediatrics
  • Spinal muscular atrophy

ASJC Scopus subject areas

  • Clinical Neurology
  • Physiology (medical)
  • Cellular and Molecular Neuroscience
  • Physiology


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