Quantitative muscle MRI in sporadic inclusion body myositis (sIBM)

<p>Background: Sporadic inclusion body myositis (sIBM) is the most common idiopathic inflammatory myopathy (IIM) in older adults. Limitations of classical clinical assessments have been cited as possible explanations for failed clinical trials, highlighting the need for more sensitive outcome measures. Quantitative muscle MRI (qMRI) is a promising tool for evaluating and monitoring sIBM.</p><p>Objective: Longitudinal assessment of qMRI in sIBM patients.</p><p>Methods: We evaluated fifteen lower extremity muscles in 12 sIBM patients (5 females, mean age 69.6, BMI 27.8) and 12 healthy age- and gender-matched controls. Seven patients and their matched controls underwent a follow-up evaluation after one year. Clinical assessment included testing for muscle strength using the Quick Motor Function Measure (QMFM), the IBM functional rating scale (IBM-FRS), and gait analysis (6-minute walking distance). 3T-MRI scans of the lower extremities were performed, including a Dixon-based sequence, T2 mapping, and diffusion tensor imaging. The qMRI parameters—fat fraction (FF), water T2 relaxation time (wT2), fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (λ1), and radial diffusivity (RD)—were analyzed.</p><p>Results: Compared to healthy controls, significant differences for all qMRI parameters averaged across all muscles were found in sIBM using a MANOVA (p < 0.001). In low-fat muscles (FF < 10%), a significant increase in wT2 and FA, accompanied by a decrease in MD, λ1, and RD, was observed (p ≤ 0.020). The strongest correlation with clinical assessments was found for wT2 values in thigh muscles (r ≤ −0.634). Significant changes in FF (+3.0%), wT2 (+0.6 ms), MD (−0.04 × 10^(−3) mm²/s), λ1 (-0.05 × 10⁻³ mm²/s), and RD (-0.03 × 10⁻³ mm²/s) were observed in the longitudinal evaluation of sIBM patients (p ≤ 0.001). FA showed no significant change (p = 0.242).</p><p>Conclusion: qMRI metrics correlate with clinical findings and can reflect different ongoing pathophysiological mechanisms. While wT2 is an emerging marker of disease activity, the role of diffusion metrics—which may reflect changes in fiber size and intracellular deposits—remains subject to further investigation.</p>

DOI 10.3233/jnd-240053

PMID 39031378

Scopus ID 2-s2.0-85203457562

WoSID 001411212600008

ORCID Source bibliographie.ub.rub.de/work/404780