Limb girdle muscular dystrophy: an interval study of weakness and functional impairment

Prospective studies of the natural history of a myopathy are effective means of measuring the status and progression of disease. This 10-year interval study of progressive weakness and functional decline was aimed to document the natural course of clinically well-characterized limb girdle muscular dystrophy in South Africa.

The manual muscle test (MMT) was used to evaluate limb strength; global strength was measured by the average muscle score (AMS). A nonlinear functional grading system was used to measure impairment of the arms and legs. An activities of daily living (ADL) scale was used to assess disability across multiple functional domains in a home environment.

The mean AMS deteriorated from 5.9 to 4.9 (on a 10-point scale) and was unrelated to patient age and disease duration. Most (78%) patients lost arm function. All patients maintained useful hand function. Two thirds of patients lost leg function. Half of the patients were wheelchair bound, and they reached this level of function around the end of their fourth decade of life. Every patient showed functional deterioration on the ADL scale. The mean score worsened from 65.6 to 77.2 (out of 156 points). The disability change was most pronounced in patients who became wheelchair bound.

This interval analysis showed a significant decline of limb strength that was independent of patient age or duration of disease and was more rapid in stronger patients. A functional grading system detected decline and was a useful measure of deterioration when applied to patients over intervals. An ADL assessment ascertained a significant functional decline across multiple functional domains in a home environment and allowed us to advise patients on compensatory strategies to limit dependence.