Neck flexor muscle strength and its relation with functional performance in Duchenne muscular dystrophy

The aim of this study was to investigate the relationship between neck flexor muscle strength and functional performance in children with DMD.

A total of 70 children with DMD between Level 1 and 3 according to Brooke Lower Extremity Functional Classification (BLEFC) were included in the study. Children were divided into 2 groups according to neck flexor strength measured by Medical Research Council Scale as Group 1 (3⁻ and below) and Group 2 (3 and above). Functional performance was assessed by 6 Minute Walk Distance (6MWD) and timed performance tests, and ambulatory status by North Star Ambulatory Assessment (NSAA). Correlations between neck flexor strength and performance tests were analyzed by using Spearman's correlation coefficient in non-parametric conditions.

Thirty-six and 34 children were included in Group 1 and 2, respectively. No statistically significant difference was found in BLEFC between groups (z = -1.225, p > 0.05). 6MWD (z = -2.574, p = 0.01) was found to be longer and NSAA (z = -2.565, p = 0.01) was higher in Group 2. Positive, moderate, statistically significant correlations were determined between neck flexor muscle strength and 6MWD (p < 0.01, r = 0.374); NSAA (p < 0.01, r = 0.399) while a negative, weak correlation between neck flexor muscle strength and the duration for standing from supine position (p = 0.02, r = -0.290).

The results indicate the relationship of neck flexor muscle strength and functional performance in DMD children. It is thought that the approaches to maintain neck flexor muscle strength from the early stages of disease process may support functional activities of daily life with less compensation and effort in DMD.