Sphincter electromyography in diagnosis of multiple system atrophy: technical issues

Muscle Nerve. 2004 Jan;29(1):151-6. doi: 10.1002/mus.10478.


Possible technical reasons for the controversy over the role of sphincter electromyography (EMG) in the diagnosis of multiple system atrophy (MSA) were analyzed. In a review of the literature, a high sensitivity (>60%) was found reported in 11 studies that included late components, and no value of the test was found in 4 studies that excluded them. This was also corroborated in a pilot study of 5 patients with probable MSA. With late components included, the mean motor unit potential (MUP) duration was prolonged in all 4 patients with an adequate single-MUP analysis sample and, with late components excluded, in 2 of 5 patients on multi-MUP analysis. At least in diagnostic EMG of MSA patients, late components should be included in the measurement of MUP duration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Aged
  • Anal Canal / physiopathology*
  • Diagnosis, Differential
  • Diagnostic Errors / prevention & control*
  • Electromyography / instrumentation
  • Electromyography / methods*
  • Electromyography / standards
  • Female
  • Humans
  • Male
  • Middle Aged
  • Multiple System Atrophy / diagnosis*
  • Multiple System Atrophy / physiopathology
  • Muscle Contraction / physiology
  • Parkinson Disease / diagnosis
  • Parkinson Disease / physiopathology
  • Pilot Projects
  • Predictive Value of Tests
  • Reaction Time / physiology
  • Reproducibility of Results