Magnetic resonance imaging of denervated muscle: comparison to electromyography

The purpose of the study is to further assess the usefulness of short TI (time to inversion) recovery (STIR) magnetic resonance imaging (MRI) in detecting denervation of skeletal muscle compared to needle electromyography (EMG). Ninety subjects with clinical evidence of peripheral nerve injury or radiculopathy underwent STIR MRI and EMG of the affected limb. In 74 (82%) of these subjects, a positive correlation was found between STIR MRI and EMG (P < 0.009). STIR MRI has a relative sensitivity of 84% and specificity of 100% for detecting denervation. A subset of 28 subjects underwent quantitative assessments of signal intensity ratio (SIR) from the STIR MRI. The rank order correlation coefficient between the SIR and abnormal spontaneous activity on EMG was 0.70 (P < 0.001). Increased signal intensity on STIR MRI corresponds closely with spontaneous activity on EMG in denervated muscle. Although less sensitive than EMG in detecting muscle denervation, STIR MRI may be a useful adjunctive diagnostic tool in this setting.