The authors describe the histopathologic and corresponding late gadolinium enhancement (LGE) MR imaging findings in whole-heart autopsy and transplantation specimens from individuals with primary or secondary cardiomyopathies and review the T1 mapping techniques used to overcome the drawbacks of LGE in diffuse myocardial diseases. Cardiac magnetic resonance (MR) imaging with late gadolinium enhancement (LGE) is used to detect and assess the myocardial damage seen with a variety of cardiomyopathies. Gadolinium-based contrast material accumulates in the expanded interstitial space of the myocardium. Areas with LGE correspond to replacement fibrosis, fibrofatty change, epithelioid granuloma, inflammatory cell infiltration, cardiomyocyte necrosis, and amyloid deposition—conditions that represent a focal increase in interstitial space. Areas without LGE correspond to interstitial or plexiform fibrosis, mildly degenerated cardiomyocytes, inflammatory cell infiltration, and diffuse amyloid deposition—conditions that represent diffuse increases in interstitial space. LGE MR imaging cannot depict these diffuse changes and does not enable quantitative evaluation of this increased interstitial space because on inversion-recovery MR images, the inversion time is adjusted to null the signal from normal-appearing or the least enhancing regions o...

Background/Objectives: Nusinersen is a disease-modifying drug for spinal muscular atrophy (SMA) that improves motor function. However, its effects on the skeletal muscles remain unclear. This study aimed to assess the intramuscular fat fraction in patients with SMA types II and III using muscle magnetic resonance imaging (MRI) and to explore the relationship between muscle tissue, lipid metabolism, and motor function during nusinersen treatment. Methods: This study included seven pediatric patients with SMA types II and III who received nusinersen treatment. Muscle MRIs were performed at three time points. Images of the central thigh were used to measure the cross-sectional area (CSA) and muscle fat area, and the intramuscular fat fraction (IMFF) was calculated. The thigh muscles were categorized into three groups: quadriceps, adductor, and hamstrings. Results: The median (range) of total IMFF for SMA type II and III at T-0, T-2, and T-4 were 18.5 (12.6–48.4), 24.4 (10.1–61.4), and 39.0 (30.0–68.6) % and increased over time. In five patients whose motor function was evaluated, a moderate negative correlation was observed between the changes in the Hammersmith Functional Motor Score Expanded (HSFME) and IMFF (r = −0.51). No significant changes in serum triglyceride or total cholesterol levels were observed during treatment. Conclusions: An increase in IMFF was associated with a decline in motor function. The baseline IMFF score was related to improvements in motor function scores, suggesting that the IMFF of the thigh muscle may serve as a novel, objective, and quantitative skeletal muscle-related biomarker for predicting the effects of nusinersen on muscle tissue.