Abstract
Introduction: Non-dystrophic myotonia (NDM) is characterized by myotonia without muscle wasting. A standardized quantitative myotonia assessment (QMA) is important for clinical trials. Methods: Myotonia was assessed in 91 individuals enrolled in a natural history study using a commercially available computerized handgrip myometer and automated software. Average peak force and 90% to 5% relaxation times were compared with historical normal controls studied with identical methods. Results: Thirty subjects had chloride channel mutations, 31 had sodium channel mutations, 6 had DM2 mutations, and 24 had no identified mutation. Chloride channel mutations were associated with prolonged first handgrip relaxation times and warm-up on subsequent handgrips. Sodium channel mutations were associated with prolonged first handgrip relaxation times and paradoxical myotonia or warm-up, depending on underlying mutations. DM2 subjects had normal relaxation times but decreased peak force. Sample size estimates are provided for clinical trial planning. Conclusion: QMA is an automated, non-invasive technique for evaluating myotonia in NDM.
Original language | English (US) |
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Pages (from-to) | 482-489 |
Number of pages | 8 |
Journal | Muscle and Nerve |
Volume | 46 |
Issue number | 4 |
DOIs | |
State | Published - Oct 2012 |
Keywords
- Ion channel mutation
- Muscle disease
- Myotonia
- Natural history
- Non-dystrophic myotonia
ASJC Scopus subject areas
- Physiology
- Clinical Neurology
- Cellular and Molecular Neuroscience
- Physiology (medical)