Magnetic resonance imaging pattern recognition in sporadic inclusion-body myositis.

Introduction: In sporadic inclusion-body myositis (IBM), additional tools are needed to confirm the diagnosis, particularly in clinically atypical or pathologically unproven patients. The aims of this study were to define the pattern of muscle MRI in IBM and to assess its accuracy in differentiating IBM from other myopathies that overlap with it clinically or pathologically.

Methods: Blind assessment was done on the scans of 17 definite IBM, 2 possible IBM, and 118 patients with other myopathies.

Results: The diagnostic accuracy to detect definite IBM was 95% for the typical pattern (with 100% specificity) and 97% for both typical and consistent patterns (with 97% specificity).

Conclusions: Muscle MRI is an accurate tool for diagnostic work-up of suspected IBM patients and may be particularly helpful in patients with early disease or who lack the classical IBM pathology.