MR Imaging of Atraumatic Muscle Disorders

Area of Science:

• Musculoskeletal Radiology
• Neuromuscular Imaging

Background:

• Atraumatic skeletal muscle disorders encompass a wide range of conditions including congenital, inherited, acquired, neoplastic, and atrophic processes.
• Differentiating these disorders using magnetic resonance (MR) imaging is challenging due to overlapping imaging features.

Purpose of the Study:

• To organize atraumatic muscle disorders into four distinct MR imaging patterns.
• To highlight key clinical and imaging findings for each pattern to aid radiologists.

Main Methods:

• Classification of muscle disorders into four MR imaging patterns: abnormal anatomy, edema/inflammation, mass, and atrophy.
• Correlation of imaging findings with clinical and laboratory data.

Main Results:

• Abnormal anatomy variants lack signal intensity changes and can be overlooked.
• Muscle edema is common but nonspecific; symmetric patterns suggest autoimmune/drug-induced myositis, while asymmetric patterns suggest infection or radiation injury.
• Intramuscular masses require biopsy for definitive diagnosis in many cases, though some lesions are distinctive.
• Atrophy is an end-stage finding in severe muscle diseases.

Conclusions:

• An imaging-based classification of atraumatic muscle disorders into four patterns aids radiological interpretation.
• Correlation with clinical and laboratory data is crucial for accurate diagnosis.