Skeletal muscle magnetic resonance biomarkers in GNE myopathy
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Abstract
Objectives To characterize muscle involvement and evaluate disease severity in patients with GNE myopathy using skeletal muscle MRI and proton magnetic resonance spectroscopy (1H-MRS).
Methods Skeletal muscle imaging of the lower extremities was performed in 31 patients with genetically confirmed GNE myopathy, including T1-weighted and STIR images, T1 and T2 mapping and 1H-MRS. Measures evaluated included longitudinal relaxation time (T1), transverse relaxation time (T2), and 1H-MRS fat fraction (FF). Thigh muscle volume was correlated with relevant measures of strength, function, and patient-reported outcomes.
Results The cohort was representative of a wide range of disease progression. Contractile thigh muscle volume ranged from 5.51% to 62.95%, and correlated with thigh strength (r = 0.91), the 6-minute walk test (r = 0.82), the adult myopathy assessment tool (r = 0.83), the activities-specific balance confidence scale (r = 0.65), and the inclusion body myositis functional rating scale (r = 0.62). Four stages of muscle involvement were distinguished by qualitative (T1W and STIR images) and quantitative methods: stage I) Unaffected muscle (T1 = 1,033 ± 74.2 ms, T2 = 40.0 ± 1.9 ms, FF = 7.4 ± 3.5%); Stage II) STIR hyperintense muscle with minimal or no fat infiltration (T1 = 1,305 ± 147 ms, T2 = 50.2 ± 3.5 ms, FF = 27.6 ± 12.7%); Stage III) Fat infiltration and STIR hyperintensity (T1 = 1,209 ± 348 ms, T2 = 73.3 ± 12.6 ms, FF = 57.5 ± 10.6%); and Stage IV) Complete fat replacement (T1 = 318 ± 39.9 ms, T2 = 114 ± 21.2 ms, FF = 85.6 ± 4.2%). 1H-MRS showed a significant decrease in intramyocellular lipid and trimethylamines (TMA) between stage I and II, suggesting altered muscle metabolism at early stages.
Conclusion MRI biomarkers can monitor muscle involvement and determine disease severity non-invasively in patients with GNE myopathy.
ClinicalTrials.gov Identifier NCT01417533.
- Received June 11, 2020.
- Accepted in final form September 30, 2020.
- © 2020 American Academy of Neurology
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