The significance of pathological spontaneous activity in various myopathies

Clin Neurophysiol. 2014 Jul;125(7):1485-90. doi: 10.1016/j.clinph.2013.11.021. Epub 2013 Dec 2.

Abstract

Objective: Pathological spontaneous activity (PSA) in electromyography (EMG) has not yet been systematically analysed in various types of myopathies.

Methods: 136 Patients with well-defined myopathies were retrospectively analysed for the presence of PSA in distal, proximal, and paravertebral muscles. PSA comprised fibrillations (fib)/positive sharp waves (PSW) and high frequency discharges (HFD; i.e., myotonic and complex repetitive discharges).

Results: fib/PSW occurred more frequently than HFD. HFD were rarely myotonic in nature. 50% and more patients presented with HFD in PROMM (80%), Pompe's disease (70%), matrin-3 myopathy (60%), sIBM (50%), CNM (50%), while far less than 50% of the patients showed RD in LGMD2I (21%), LGMD2A (17%), LGMD2B (17%), LGMD2L (14%), FSHD (4%), BMD (0%). Four different HFD patterns were proposed.

Conclusion: The segregation of myopathies relative to the occurrence of PSA and especially HFD in a high prevalence group and in a low prevalence group may be diagnostically valuable.

Significance: The screening for HFD by means of EMG is also valuable in the diagnosis of non-myotonic myopathies.

Keywords: Complex repetitive discharges; Electromyography; Limb girdle muscular dystrophy; Matrin 3 myopathy; Myotonic discharges.

MeSH terms

  • Adult
  • Electromyography*
  • Female
  • Glycogen Storage Disease Type II / diagnosis
  • Glycogen Storage Disease Type II / physiopathology
  • Humans
  • Male
  • Middle Aged
  • Muscular Diseases / diagnosis*
  • Muscular Diseases / physiopathology
  • Muscular Dystrophies, Limb-Girdle / diagnosis
  • Muscular Dystrophies, Limb-Girdle / physiopathology
  • Retrospective Studies

Supplementary concepts

  • Limb-girdle muscular dystrophy type 2A
  • Limb-girdle muscular dystrophy, type 2B
  • Muscular Dystrophy, Limb-Girdle, Type 2I
  • Muscular Dystrophy, Limb-Girdle, Type 2L