Denervation syndromes of the shoulder girdle: MR imaging with electrophysiologic correlation

Objective. To investigate the use of MR imaging in the characterization of denervated muscle of the shoulder correlated with electrophysiologic studie s. Design and patients. We studied with MR imaging five patients who presented with shoulder weakness and pain and who underwent electrophysiologic studi es. On MR imaging the distribution of muscle edema and fatty infiltration w as recorded, as was the presence of masses impinging on a regional nerve. Results. Acute/subacute denervation was best seen on T2-weighted fast spin- echo images with fat saturation, showing increased SI related to neurogenic edema. Chronic denervation was best seen on T1-weighted spin-echo images, demonstrating loss of muscle bulk and diffuse areas of increased signal int ensity within the muscle. Three patients showed MR imaging and electrophysi ologic findings of Parsonage Turner syndrome. One patient demonstrated an a rteriovenous malformation within the spinoglenoid notch, impinging on the s uprascapular nerve with associated atrophy of the infraspinatus muscle. The fifth patient demonstrated fatty atrophy of the teres minor muscle caused by compression by a cyst of the axillary nerve and electrophysiologic findi ngs of an incomplete axillary nerve block. Conclusion. MR imaging is useful in detecting and characterizing denervatio n atrophy and neurogenic edema in shoulder muscles. MR imaging can provide additional information to electrophysiologic studies by estimating the age (acute/chronic) and identifying morphologic causes for shoulder pain and at rophy.