Radiographic patterns of muscle involvement in the idiopathic inflammatory myopathies

Abstract

Introduction This study assesses the burden, distribution, and evolution of muscle inflammation and damage on MRI among subtypes of idiopathic inflammatory myopathy (IIM). Methods Musculoskeletal MRIs performed in 66 patients with IIM and 10 patients with non‐IIM between 2009 and 2016 were retrospectively graded for muscle edema, fatty replacement (FR), and atrophy. Results Immune‐mediated necrotizing myopathy (IMNM) patients had severe and extensive lower limb muscle edema, FR, and atrophy. The pelvic muscles and adductors were significantly more affected than in patients with dermatomyositis and polymyositis. Inclusion body myositis (IBM) was characterized by marked anterior thigh involvement, which stabilized or progressed at follow‐up imaging. Atrophy and FR grades improved over time in some non‐IBM IIM patients. Discussion Patients with IMNM and IBM have characteristic patterns of muscle MRI abnormalities that may allow them to be differentiated radiologically from other IIM subtypes. Muscle damage in non‐IBM IIM may be reversible.

Investigating the Association Between Muscular Ultrasonographic Alterations and Clinical Symptoms in Patients With Inflammatory Myopathy

“…A. Day et al, 2019). A similar result was observed in this study, finding an association merely between EI and dynamometry score of the distal compartment.…”

Multiexponential Analysis of the Water T2‐Relaxation in the Skeletal Muscle Provides Distinct Markers of Disease Activity Between Inflammatory and Dystrophic Myopathies

“…Nonetheless, T 2 maps offer much better spatial coverage than single‐voxel MRS. Multislice acquisitions allow evaluating all different muscles individually and through their whole length in a single acquisition. This is an important advantage of MRI over single‐voxel MRS, especially in the case of NMDs, which are usually characterized by heterogeneous muscle involvement 31,32 . Moreover, MRI offers the possibility for texture analysis, which has already shown promising results regarding the classification of muscular dystrophy subtypes 33 …”

“…This is an important advantage of MRI over single-voxel MRS, especially in the case of NMDs, which are usually characterized by heterogeneous muscle involvement. 31,32 Moreover, MRI offers the possibility for texture analysis, which has already shown promising results regarding the classification of muscular dystrophy subtypes. 33 However, to our knowledge, most available water T 2 mapping methods assume a monoexponential model for the water T 2 -relaxation in skeletal muscle.…”

Idiopathic inflammatory myopathies: a review

“…The pattern of radiological muscle damage can help determine disease subtype. Patchy involvement can occur in DM 23 . Fascial and subcutaneous oedema is characteristic of DM, although if occurring in dependent areas, disuse and other non‐inflammatory conditions should be considered as differentials 23 .…”

“…IBM tends to show involvement of vastus, sparing rectus femoris. NAM commonly involves the pelvis and adductor muscles which are relatively spared in DM 23 . Additionally, MRI can detect subclinical inflammation or conversely a non‐inflammatory myopathic process if muscle oedema is absent in a clinically weak patient.…”