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Distinguishing paramyotonia congenita and myotonia congenita by electromyography
Author(s) -
Subramony S. H.,
Malhotra C. P.,
Mishra S. K.
Publication year - 1983
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.880060506
Subject(s) - myotonia congenita , electromyography , compound muscle action potential , myotonia , medicine , motor unit , cardiology , stimulation , anesthesia , physical medicine and rehabilitation , electrophysiology , anatomy , myotonic dystrophy
Compound muscle action potential (CMAP) amplitudes, response to 2 Hz nerve stimulation, response to exercise and electromyographic needle electrode examination findings from the thenar muscles of two patients with paramyotonia congenita were compared with those from two patients with dominantly inherited myotonia congenita in warm (34°C) and cold (20°C) states. Cold induced a significant fall in CMAP amplitude, induced/worsened a significant decremental response to 2 Hz stimulation, and virtually abolished myotonia and voluntary recruitment of motor unit potentials in patients with paramyotonia congenita; none of these occurred in myotonia congenita. Though exercise induced a mild fall in CMAP amplitude in both groups, postexercise fibrillations occurred only in patients with paramyotonia congenita. These findings serve to distinguish these two entities in the clinical electromyography laboratory.