Two Cases of Plexitis in a Day-MRI

Case I : Patient presented with foot drop with abnormal high signal on T2/STIR images involving the right gluteal muscles and piriformis with fluid signal consistent with acute denervation changes. There is evidence of thickening and high signal intensity in the right sciatic nerve with high signal in the sacral plexus.  These findings may be indicate LS plexopathy/plexitis.

Case 2 Patient with Hepatitis C presented with left arm numbness shows evidence of abnormal high signal involving the left brachial plexus trunks which may indicate acute brachial plexitis (possibly viral in etiology). No obvious denervation changes noted in the scalene muscles and muscles of the shoulder girdle.