Upper extremity functional rating for patients with Duchenne muscular dystrophy

Area of Science:

• Neurology
• Pediatrics
• Musculoskeletal Disorders

Background:

• Duchenne muscular dystrophy (DMD) is a progressive genetic disorder characterized by muscle weakness.
• Upper extremity strength and function significantly decline with age in individuals with DMD.
• Understanding the relationship between strength and function is crucial for managing DMD progression.

Purpose of the Study:

• To evaluate the age-related deterioration of upper extremity strength and function in boys with DMD.
• To determine the relationship between average strength and functional capability in this population.
• To assess the utility of the Brooke upper extremity grading scale in describing DMD natural history.

Main Methods:

• Twenty-eight boys with DMD participated in the study.
• Manual Muscle Testing (MMT) assessed upper extremity strength.
• The Brooke upper extremity grading scale evaluated functional capability.

Main Results:

• Mean MMT showed a logarithmic decline with age (0.9% decrease per 1% age increase).
• Functional grade progression varied by age group, with significant deterioration observed after age 13.
• A strong correlation was found between mean MMT and functional grade, with rapid decline past a strength threshold.

Conclusions:

• The Brooke scale effectively describes upper extremity function in DMD, potentially with three distinct grades.
• DMD natural history shows rapid functional decline in early adolescence as strength loss surpasses compensatory mechanisms.
• Functional deterioration accelerates when muscle strength falls below a critical threshold, leading to rapid functional loss.