Magnetic resonance imaging of ulnar nerve abscess in leprosy: a case report.

A 14-year-old girl on multidrug treatment for borderline tuberculoid leprosy presented with a swelling in her left arm and soon thereafter developed ulnar claw hand. MRI showed a well-defined ovoid lesion arising from the left ulnar nerve, isointense to muscle on T1W images and hyperintense on T2W and STIR images. On post gadolinium T1W sequence the lesion showed peripheral rim enhancement with central necrosis suggestive of abscess. The ulnar nerve proximal and distal to the lesion was thickened and showed mild contrast enhancement. On aspiration the swelling yielded frank pus which was positive for acid-fast bacilli.