Step Activity Monitoring in Boys with Duchenne Muscular Dystrophy and its Correlation with Magnetic Resonance Measures and Functional Performance

Article type: Research Article

Authors: Nair, Kavya S.^a | Lott, Donovan J.^{a; *} | Forbes, Sean C.^a | Barnard, Alison M.^a | Willcocks, Rebecca J.^a | Senesac, Claudia R.^a | Daniels, Michael J.^b | Harrington, Ann T.^c | Tennekoon, Gihan I.^d | Zilke, Kirsten^e | Finanger, Erika L.^e | Finkel, Richard S.^f | Rooney, William D.^g | Walter, Glenn A.^h | Vandenborne, Krista^a

Affiliations: [a] Department of Physical Therapy, University of Florida, Gainesville, FL, USA | [b] Department of Statistics, University of Florida, Gainesville, FL, USA | [c] Center for Rehabilitation, Children’s Hospital of Philadelphia, Philadelphia, PA, USA | [d] Department of Neurology and Pediatrics, Children’s Hospital of Philadelphia, Philadelphia, PA, USA | [e] Department of Pediatrics and Neurology, Oregon Health & Science University, Portland, OR, USA | [f] Center for Experimental Neurotherapeutics, St. Jude Children’s Research Hospital, Memphis, TN, USA | [g] Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR, USA | [h] Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, USA

Correspondence: [*] Correspondence to: Donovan J. Lott, University of Florida, College of Public Health & Health Professions, Department of Physical Therapy, Box 100154, UFHSC, Gainesville, FL 32610-0154, USA. Tel.: +1 352 273 9226; Fax: 352 273 6109; E-mail: [email protected].

Abstract: Background:Muscles of boys with Duchenne muscular dystrophy (DMD) are progressively replaced by fatty fibrous tissues, and weakness leads to loss of ambulation (LoA). Step activity (SA) monitoring is a quantitative measure of real-world ambulatory function. The relationship between quality of muscle health and SA is unknown in DMD. Objective:To determine SA in steroid treated boys with DMD across various age groups, and to evaluate the association of SA with quality of muscle health and ambulatory function. Methods:Quality of muscle health was measured by magnetic resonance (MR) imaging transverse magnetization relaxation time constant (MRI-T2) and MR spectroscopy fat fraction (MRS-FF). SA was assessed via accelerometry, and functional abilities were assessed through clinical walking tests. Correlations between SA, MR, and functional measures were determined. A threshold value of SA was determined to predict the future LoA. Results:The greatest reduction in SA was observed in the 9– < 11years age group. SA correlated with all functional and MR measures.10m walk/run test had the highest correlation with SA. An increase in muscle MRI-T2 and MRS-FF was associated with a decline in SA. Two years prior to LoA, SA in boys with DMD was 32% lower than age matched boys with DMD who maintained ambulation for more than two-year period. SA monitoring can predict subsequent LoA in Duchenne, as a daily step count of 3200 at baseline was associated with LoA over the next two-years. Conclusion:SA monitoring is a feasible and accessible tool to measure functional capacity in the real-world environment.

Keywords: Step activity, MRI, fat fraction, duchenne muscular dystrophy, 10m walk/run test

DOI: 10.3233/JND-210746

Journal: Journal of Neuromuscular Diseases, vol. 9, no. 3, pp. 423-436, 2022