Muscle ageing involves structural and functional changes of muscles, mainly their replacement by fatty and fibrous tissue accompanied by the loss of muscle function. Quantitative magnetic resonance imaging (qMRI) methods have potential to provide biomarkers of degenerative changes in muscles with ageing. To assess the relationship between qMRI parameters of lumbar paraspinal muscles (LPMs) and their function and evolution with ageing in healthy subjects, 90 volunteers underwent MRI of lumbar spine and LPM utilising a 6-point Dixon gradient echo sequence. Using manual muscle segmentation, fat fraction (FF) and functional muscle volume (FMV) were calculated for LPM, with the psoas muscle (PS) as a control muscle. Functional parameters of LPM (strength and endurance) were assessed. Based on our data analysis, both FF and FMV of LPM correlate significantly with maximal isometric lumbar extensor muscle strength, but not with endurance. With ageing, FF of LPM increases by 34% per decade, while FF of PS increases by 17% per decade. This difference between LPM and the PS in the rate of FF increase is significant. FMV evinces a decreasing trend in both LPM and PS. However, only FMV of PS decreases significantly by 7% per decade. Our cross-sectional study shows a significant correlation between qMRI parameters of LPM and their strength. FF appears to be a biomarker of muscle ageing with different ageing patterns of distinct muscle groups: LPM and PS.

• Keywords
• Magnetic resonance imaging (MRI), ageing, endurance, muscle strength, paraspinal muscles,
• Publication type
• Journal Article MeSH

INTRODUCTION: Muscle magnetic resonance imaging (MRI) is an emerging method in the diagnosis and monitoring of muscular dystrophies. This cross-sectional, comparative study aimed to evaluate quantitative MRI (qMRI) parameters of the lumbar paraspinal muscles (LPM) in myotonic dystrophy type 2 (DM2), to assess their relationship with functional examination, and to evaluate their evolution with aging. METHODS: The study enrolled 37 DM2 patients and 90 healthy volunteers (HV) who were matched based on physiological parameters to create 35 pairs. Utilizing a 6-point Dixon gradient echo sequence MRI, fat fraction (FF), total muscle volume, and functional muscle volume (FMV) of the LPM and psoas muscle (PS) were obtained. Using correlation coefficients and regression models, the relationship between MRI and the maximal isometric lumbar extensor muscle strength (MILEMS) and lumbar extensor muscle endurance (LEME), and their evolution with age, were assessed. RESULTS: LPM showed significantly higher FF in DM2 patients compared to HV (21.3% vs. 11.3%, p-value <0.001). FMV of LPM correlated significantly with MILEMS (ρ = 0.5, p- value = 0.001) and FF with LEME (ρ = -0.49, p- value = 0.002) in DM2. No significant differences in the rate of deterioration in functional and morphological parameters of the LPM with age were observed between the two groups. CONCLUSION: We demonstrated morphological correlates of lumbar extensor muscle dysfunction in DM2 patients. The qMRI parameters of LPM correlated with functional parameters but could not be used either as a reliable biomarker of lumbar extensor muscle impairment or as a biomarker of disease progression.

• Keywords
• endurance, magnetic resonace imaging, muscle strengh, myotonic dystrophy type 2, paraspinal muscles,
• Publication type
• Journal Article MeSH