Absent, unrecognized, and minimal myotonic discharges in myotonic dystrophy type 2

Nathan P. Young, Jasper R. Daube, Eric J. Sorenson, Margherita Milone

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

The purpose of this study was to describe the frequency of absent, unrecognized, or minimal myotonic discharges (MDs) in myotonic dystrophy type 2 (DM2). We performed a retrospective review of needle electromyography (EMG) data prior to genetic diagnosis in 49 DM2 patients at the Mayo Clinic. MDs were not reported on first or repeat EMG studies (n = 8) and not found in archived recordings of 4 patients (8%); archived EMG recordings (n = 4) confirmed the absence of MDs (n = 2), including 1 patient with normal insertional activity in all muscles, and misinterpretation of MDs as slow fibrillation potentials (n = 1) and complex repetitive discharge (CRD) activity (n = 1). Eight (16%) patients had minimal classic MDs with diffusely increased insertional activity, including waning-only MDs in all patients in this group with archived EMG recordings (n = 5). Diffuse MDs were found in 33 (67%) patients. Absent or minimal MDs do not exclude DM2. Over-reliance on diffuse MDs in patients who present with myopathy may lead to delay in genetic diagnosis of DM2.

Original languageEnglish (US)
Pages (from-to)758-762
Number of pages5
JournalMuscle and Nerve
Volume41
Issue number6
DOIs
StatePublished - Jun 1 2010

Keywords

  • Electromyography
  • Myotonic discharges
  • Myotonic dystrophy type 2
  • Proximal myotonic myopathy

ASJC Scopus subject areas

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

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