Myotonic dystrophy (dystrophia myotonica; DM), the most prevalent form of muscular dystrophy in adults, is characterized by progressive myopathy, myotonia, and multi-systemic involvement. DM causes severe disability and profoundly affects the patient's quality of life. Currently, no effective treatments are available that alter the course of the disease, but ongoing clinical trials are underway.
Age 18 - 65 years
Diagnosis of DM1 or DM2 by clinical or genetic criteria. If DM1 or DM2 was diagnosed by clinical criteria, a first-degree relative must have genetic testing confirmation and sign a genetic consent form to release their genetic information
Clinically affected, as defined by muscle weakness or myotonia
Ambulate independently (a walker is not permitted)
Cardiac pacemaker, defibrillator, metal implants, or other contraindications for MRI
Use of anabolic or catabolic agents within one year of entry
History of lumbar spine or leg surgery, lumbar radiculopathy, or peripheral neuropathy
BMI > 35 because obesity compromises positioning on the MR scanner
The selection criteria will minimize the heterogeneity effects and mirror DM subjects likely to be selected for clinical trials, who are typically mildly to moderately affected. Subjects will be recruited from the Wake Forest Neuromuscular Clinic and nearby medical centers (Duke University, UNC Chapel Hill, and Atrium Health in Charlotte). Since DM2 is rarer than DM1 and patients live across the country, additional recruitment efforts will target DM2 subjects through the Myotonic Dystrophy Foundation Family Registry (MDFR).
Case-control
Prospective
Not listed
Contractile muscle volume (CMV, cm3)
Contractile muscle volume (CMV, cm3) of individual muscles and the total CMV within the thigh (anterior, medial, posterior) and calf (anterior, lateral, posterior) compartments
Muscle fat fraction (MFF, %)
Muscle fat fraction (MFF, %) of individual muscles and the total CMV within the thigh (anterior, medial, posterior) and calf (anterior, lateral, posterior) compartments
Average measures of Manual muscle testing (MMT)
MMT will be performed in 7 different muscle groups (hip flexors, hip abductors, knee flexors, knee extensors, ankle dorsiflexors, plantar flexors, and neck flexor) in standardized positions. Each group will be scored using a 13-point modified Medical Research Council (MRC) scale and standardized positions. Where 0 is paralysis, 1 is a flicker/trace contraction, 2 is movement with gravity eliminated, 3 is movement against gravity, 4 is movement against some resistance, and 5 is normal strength against full resistance - higher scores denoting stronger muscles
Average measures of Quantitative Muscle Testing (QMT)
QMT of the leg muscles (hip flexors, hip abductors, knee extensors, knee flexors, ankle dorsiflexors, and plantar flexors) will be performed using a hand-held dynamometer in standardized positions. During the measurement, the subject will be instructed to increase to maximum exertion over a few seconds without jerking, and to maintain this effort until the evaluator give the command to relax (3-5 seconds). The clinical evaluator will hold the dynamometer stable, and the subject will be asked to push as hard as possible against the applicator, but with a slow build-up of force. The subject will perform each push three times with up to a 30-second pause between each trial. The average and highest scores obtained will be used for analysis.
Average measures of grip strength (pounds or kilograms)
Use Jamar handgrip dynamometer to test handgrip strength. We will test each subject three trials, starting with a dominant hand first, then a non-dominant hand. An average score in each hand will be used for analysis. Higher scores denote stronger grip strength - It works by squeezing the device to its maximum, revealing strength in pounds or kilograms (up to 200 lbs/90 kg)
Average measures of pinch strength
The subject will perform quantitative pinch strength testing with a pinch gauge - higher numbers denote stronger pinch strength - Normal range: 10-20 pounds of force
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