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Absent, unrecognized, and minimal myotonic discharges in myotonic dystrophy type 2
Author(s) -
Young Nathan P.,
Daube Jasper R.,
Sorenson Eric J.,
Milone Margherita
Publication year - 2010
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21615
Subject(s) - myotonic dystrophy , medicine , electromyography , myotonia , myopathy , physical medicine and rehabilitation , cardiology
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. Muscle Nerve, 2010