Electrical impedance myography correlates with standard measures of ALS severity

Muscle Nerve. 2014 Mar;49(3):441-3. doi: 10.1002/mus.24128. Epub 2013 Dec 19.


Introduction: Electrical impedance myography (EIM) can be used to assess amyotrophic lateral sclerosis (ALS) progression. The relationship between EIM values and standard assessment measures, however, is unknown.

Methods: EIM 50 kHz phase data from 60 subjects who participated in a longitudinal natural history study of ALS were correlated with handheld dynamometry (HHD), the ALS Functional Rating Scale-Revised (ALSFRS-R) score, and motor unit number estimation (MUNE).

Results: Moderate strength correlations between EIM parameters and HHD were observed for both whole-body and individual upper and lower extremity values. Similarly, moderate strength correlations were observed between EIM and ALSFRS-R upper and lower extremity subscores, but not total ALSFRS-R scores. MUNE correlated significantly with single muscle EIM data but not with whole body or upper or lower extremity values.

Conclusions: These results support the concept that EIM can serve as a meaningful measure of disease severity in ALS.

Keywords: ALSFRS-R; amyotrophic lateral sclerosis; biomarkers; electrical impedance myography; handheld dynamometry.

MeSH terms

  • Aged
  • Amyotrophic Lateral Sclerosis / diagnosis*
  • Amyotrophic Lateral Sclerosis / physiopathology*
  • Disease Progression
  • Electric Impedance*
  • Evoked Potentials, Motor / physiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Muscle Strength Dynamometer
  • Muscle, Skeletal / physiopathology*
  • Myography / methods*
  • Myography / standards