340P Upper extremity assessment in Becker muscular dystrophy: a functional and MRI data approach.

Becker muscular dystrophy (BMD) is a progressive disorder and impairs upper extremity (UE) function. The Performance of Upper Limb (PUL) measures UE function in muscular dystrophy, but has a ceiling effect in high-functioning subjects. Yet, fat fraction (FF) values via quantitative magnetic resonance (qMRI) have been used as biomarkers of muscle deterioration. Thus, the study aims to 1) determine if the PUL or qMRI FF can discriminate between functional groups of men with BMD and controls, and 2) assess relationships between PUL scores and qMRI FF. In a cross-sectional study, 56 men with BMD and 9 controls (18-63 yrs) completed PUL 2.0 and whole-body qMRI. Composite FF values for UE (deltoid, biceps & triceps) and whole-body were calculated. To understand the impact of mobility on UE performance, men with BMD were grouped using the 10-m run/walk test. Functional groups were: A) non-ambulatory B) walks – with no increase in speed possible; C) fast walking or jog; or D) run. One-way ANOVA/Kruskal-Wallis and Spearman's rho were used to assess differences between groups and correlations, respectively. Men with BMD scored 18-42 on the PUL. The PUL only detects differences between non-ambulatory (Group A) and high-functioning (Group C: p<0.001; Group D: p=0.02; Controls: p<0.001) groups. However, qMRI UE FF composite can discriminate between low-functioning (Groups A-B) and high-functioning (Groups C-D) men with BMD and whole-body FF composite can discriminate between all BMD functional groups (p<0.001 to 0.02). Higher PUL scores were associated with lower qMRI FF (p<0.05; rho =-0.70 to -0.50) only in low-functioning men with BMD (Groups A&B). Thus, the PUL has utility in assessing UE function in low-functioning men with BMD. Because the PUL may provide limited information about UE impairment in high-functioning men with BMD, it should be used cautiously or together with other biomarkers such as qMRI FF. [ABSTRACT FROM AUTHOR]