Funded By:
By C.M. McDonald, MD, R.T. Abresch, MS, G.T. Carter, MD,
W.M. Fowler, Jr., MD,
E.R. Johnson, MD, and D.D. Kilmer, MD.
RTC/Neuromuscular Diseases, Department of Physical Medicine & Rehabilitation, University of California, Davis, and National Inst. on Disability & Rehabilitation Research Grant H133B30026, August 1995.
Becker's muscular dystrophy (BMD) is a slowly progressive myopathy with a similar pattern of muscle weakness to Duchenne muscular dystrophy (DMD), but with later onset and a much slower rate of progression. Like DMD it has a X-linked inheritance pattern, is restricted to males, and both skeletal and cardiac muscle are involved. It also has a lower incidence than DMD with prevalence rates ranging from 12 to 27 cases per million individuals and an overall prevalence of 24 per million. While the characteristics of BMD are well known, the only previous comprehensive impairment and disability profile was reported in 1993 (Bushby, Gardner-Medwin: J Neurol 240:98). In addition, there have been few studies of the incidence and description of some of the characteristics such as contractures, spine deformity, pulmonary and cardiac function, intellectual and cognitive function, and psychosocial adjustment.
The purpose of this study was to develop a comprehensive impairment and disability profile for BMD. Impairment was evaluated by measurements of strength, contractures, spine deformity, cardiac and pulmonary function and intellectual capacity. Disability evaluations consisted of measures of mobility and upper extremity function, cardiac and pulmonary disease, and psychosocial adjustments.
Twenty individuals followed in a regional neuromuscular disease clinic, 1982-1992 were reviewed. Mean age was 26 17 years, age at onset 8.4 8.5 years, and disease duration 20 14 years at the time of the first clinic visit. Only two individuals were nonambulatory with long ambulation at 21 and 29 years. Only one individual was known to have died during the 10-year period. All participants from the clinic did not receive all measurements so the individuals in each of the impairment and disability profiles would be considered as samples of the larger clinic population.
When appropriate, results were compared with able-bodied controls and/or established reference standards. The effect of age and disease duration was evaluated by both one-time event (cross sectional) and longitudinal analyses. In the former, the first measurement obtained on every subject was plotted against years of age and disease duration. In the latter, each measurement for each individual for a three or more year period of time was analyzed. Due to the small sample size, anthropometric, quantitative strength measurements, and exercise cardiopulmonary measurements were not obtained.
Muscle Weakness Profile - Manual Muscle Tests (MMT): MMTs were obtained in 14 subjects. On the MMT scale, 5 is normal strength. The muscle group is weak but moves the joint against a combination of gravity and some resistance with a grade of 4. With a grade of 3, the muscle group cannot move against resistance, but moves the joint fully against gravity.
