Document Detail

Evoked myotonia can be "dialed-up" by increasing stimulus train length in myotonic dystrophy type 1.
MedLine Citation:
PMID:  19750543     Owner:  NLM     Status:  MEDLINE    
It is unknown how evoked myotonia varies with stimulus frequency or train length, or how it compares to voluntary myotonia in myotonic dystrophy type 1 (DM1). First dorsal interosseous (FDI) tetanic contractions evoked by trains of 10-20 ulnar nerve stimuli at 10-50 HZ were recorded in 10 DM1 patients and 10 normals. For comparison, maximum voluntary handgrip contractions were also recorded. An automated computer program placed cursors along the declining (relaxation) phase of the force recordings at 90% and 5% of peak force (PF) and calculated relaxation times (RTs) between these points. For all stimulus frequencies and train lengths, evoked RTs were much shorter, and evoked PFs were much greater in normals than in DM1. In normals, evoked RT was independent of stimulus frequency and train length, while in DM1 RT was longer for train lengths of 20 stimuli (mean: 9 s in DM1; 0.20 in normals) than for 10 stimuli (mean: 3 s in DM1, 0.19 in normals), but it did not change with stimulus frequency. In both groups PF increased greatly as stimulus frequency rose from 10-50 HZ but only slightly as train length rose from 10-20 stimuli. Voluntary handgrip RT (mean: 1.9 s) was less than evoked FDI RT (mean: 9 s). In DM1, evoked RT can be "dialed up" by increasing stimulus train length. Evoked myotonia testing utilizing a stimulus paradigm of at least 20 stimuli at 30-50 HZ may be useful in antimyotonic drug trials, particularly when grip RT is normal or equivocal.
Eric L Logigian; Paul Twydell; Nuran Dilek; William B Martens; Chris Quinn; Allen W Wiegner; Chad R Heatwole; Charles A Thornton; Richard T Moxley
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Muscle & nerve     Volume:  41     ISSN:  1097-4598     ISO Abbreviation:  Muscle Nerve     Publication Date:  2010 Feb 
Date Detail:
Created Date:  2010-01-21     Completed Date:  2010-02-17     Revised Date:  2014-08-28    
Medline Journal Info:
Nlm Unique ID:  7803146     Medline TA:  Muscle Nerve     Country:  United States    
Other Details:
Languages:  eng     Pagination:  191-6     Citation Subset:  IM    
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MeSH Terms
Case-Control Studies
Electric Stimulation
Hand Strength / physiology
Middle Aged
Muscle Contraction / physiology*
Muscle Relaxation / physiology
Muscle, Skeletal / physiopathology*
Myotonia / etiology,  physiopathology*
Myotonic Dystrophy / physiopathology*
Ulnar Nerve / physiology
Grant Support
5 MO1RR00044/RR/NCRR NIH HHS; 5U54 NSO48843-05//PHS HHS; U54 NS048843-050003/NS/NINDS NIH HHS

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