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Serial manual muscle testing in Duchenne muscular dystrophy
D D Kilmer1, R T Abresch, W M Fowler
1Department of Physical Medicine and Rehabilitation, University of California, Davis.
Archives of Physical Medicine and Rehabilitation
|November 1, 1993
Summary
Boys with Duchenne muscular dystrophy (DMD) experience linear muscle strength loss until age 14. After this, strength deterioration significantly slows, which is crucial for evaluating DMD treatments.
Area of Science:
- Neurology
- Pediatrics
- Genetics
Background:
- Duchenne muscular dystrophy (DMD) is a progressive genetic disorder characterized by muscle degeneration.
- Understanding the natural history of muscle strength loss in DMD is essential for clinical trial design and patient management.
Purpose of the Study:
- To define the natural course of muscle strength loss in boys with Duchenne muscular dystrophy.
- To investigate the relationship between strength decline, anthropometric variables, and ambulatory status.
- To identify potential inflection points in disease progression relevant to therapeutic interventions.
Main Methods:
- Serial manual muscle testing (MMT) of 34 muscle groups over up to seven years.
- Study cohort included 63 boys with DMD (mean age 11.5 years) without bracing or corrective surgery for ambulation.
- Longitudinal analysis of individual patient data and correlation with age.
Main Results:
- Muscle strength decreased linearly (-0.26 MMT units/year) until approximately age 14.
- A marked decrease in the rate of strength progression was observed after age 14 (-0.06 MMT units/year).
- Average muscle score at full-time wheelchair use was 3.0 MMT units.
Conclusions:
- The rate of muscle strength loss in DMD significantly slows around age 14.
- This age-related change in disease progression is a critical factor for assessing the efficacy of therapeutic interventions in adolescent boys with DMD.