Upper vs lower extremity functional loss in neuromuscular disease

Area of Science:

• Neurology
• Rehabilitation Medicine
• Clinical Research

Background:

• Established functional rating scales exist for upper extremity (UE) and lower extremity (LE) function in Duchenne muscular dystrophy (DMD), specifically the Brooke scale for UE and Vignos scale for LE.
• Previous research has not tested the assumption that UE functional loss parallels LE loss in neuromuscular disorders.
• The relationship between UE and LE strength has not been adequately examined in these patient populations.

Purpose of the Study:

• To test the hypothesis that UE and LE strength and functional losses are parallel in Duchenne muscular dystrophy (DMD) and other neuromuscular disorders.
• To investigate the correlation between UE and LE functional grades and strength scores across different myopathies.
• To determine if UE and LE measurements are equivalent for clinical assessment and drug trial evaluations.

Main Methods:

• Data collection included Vignos grades, Brooke grades, and manual muscle test scores.
• The study cohort comprised 27 patients with DMD, 10 with fascioscapulohumeral muscular dystrophy (FSH), 24 with myotonic muscular dystrophy (MMD), and 29 with other proximal myopathies (PM).
• Spearman correlation coefficients were calculated for UE versus LE functional grade and strength scores, with significance analysis applied.

Main Results:

• All correlations between UE and LE measures were statistically significant (p < 0.01) but not perfect (p < 0.01 for difference from one).
• Coefficients of determination showed that LE rank explained a maximum of 86% of the variation in UE rank (observed in FSH patients).
• While a significant relationship exists between UE/LE strength and functional grade, these measurements were not found to be entirely equivalent.

Conclusions:

• There is a significant relationship between upper and lower extremity strength and function in muscular dystrophies.
• However, UE and LE functional and strength measurements are not entirely equivalent.
• Lower extremity measures may serve as a substitute for UE measurements in drug trials expecting global effects, but not for individual clinical status evaluation.