Muscle diffusion tensor imaging in glycogen storage disease V (McArdle disease)

Purpose: To evaluate differences in diffusion parameters in thigh muscles in patients with glycogen storage disease type V (McArdle disease) using muscle diffusion tensor imaging (mDTI) compared to healthy controls METHODS: In this prospective study, we evaluated thigh muscles from hip to knee of 10 McArdle patients (5 female, mean age 33.7 ± 14.4 years) and 10 healthy age- and gender-matched volunteers. MRI scans were performed at 3 T and comprised mDTI, T1-weighted and T2-weighted imaging between May 2015 and May 2017. Needle biopsy of the vastus lateralis muscle was performed in three McArdle patients. The muscle tissue was analyzed by using histochemical and enzyme-histochemical techniques for glycogen content and histopathological changes. Mean values of the eigenvalues (λ₁-λ₃), fractional anisotropy (FA), and mean diffusivity (MD) were obtained for the vastus lateralis, vastus medialis, rectus femoris, biceps femoris, semitendinosus, and semimembranosus and compared between groups using Student's t tests, as well as ANCOVA; significance level was set at p < 0.05.

Results: Needle biopsy showed intracellular glycogen accumulation in skeletal muscle fibers of three McArdle patients. Extracellular histopathological changes were not found. Muscle DTI analysis did not show statistically significant differences between patients and controls for any of the muscles.

Conclusion: Despite intracellular glycogen accumulation in the three biopsy samples, mDTI parameters were not altered in McArdle patients compared to controls. We conclude that the currently used mDTI acquisition and processing lack the sensitivity to detect intracellular changes due to accumulated glycogen in this cohort of McArdle patients.

Key points: • Despite intracellular glycogen accumulation in three examined biopsy samples, mDTI parameters were not altered in McArdle patients compared to controls. • In its current form, diffusion MR does not provide additional information in quantifying intracellular glycogen accumulations within skeletal muscle fibers in McArdle patients.