Association between neurodevelopmental impairments and motor function in Duchenne muscular dystrophy

We explored various prognostic factors of motor outcomes in corticosteroid-naive boys with Duchenne Muscular Dystrophy (DMD).

The associations between parent-reported neurodevelopmental concerns (speech delay, speech and language difficulties (SLD), and learning difficulties), DMD mutation location, and motor outcomes (6-minute walk distance (6MWD), North Star Ambulatory Assessment (NSAA) total score, 10-meter walk/run velocity, and rise from floor velocity) were studied in 196 corticosteroid-naive boys from ages 4 to less than 8 years.

Participants with SLD walked 25.8 fewer meters in 6 minutes than those without SLD (p = 0.005) but did not demonstrate statistical differences in NSAA total score, 10-meter walk/run velocity, and rise from floor velocity. Participants with distal DMD mutations with learning difficulties walked 51.8 fewer meters in 6 minutes than those without learning difficulties (p = 0.0007). Participants with distal DMD mutations were slower on 10-meter walk/run velocity, and rise from floor velocity (p = 0.02) than those with proximal DMD mutations. Participants with distal DMD mutations, who reported speech delay or learning difficulties, were slower on rise from floor velocity (p = 0.04, p = 0.01) than those with proximal DMD mutations. The mean NSAA total score was lower in participants with learning difficulties than in those without (p = 0.004).

Corticosteroid-naive boys with DMD with distal DMD mutations may perform worse on some timed function tests, and that those with learning difficulties may perform worse on the NSAA. Pending confirmatory studies, our data underscore the importance of considering co-existing neurodevelopmental symptoms on motor outcome measures.