Epineural ganglion of the ulnar nerve at the elbow.

Ganglion cysts of peripheral nerves in the upper extremity are rare. Cysts located in the substance of the nerve and extraneural ganglia that cause symptomatic nerve compression have been reported. Intraneural ganglia may be difficult to separate from the neural elements without resultant nerve injury. This case involved a ganglion cyst confined to the epineurium of the ulnar nerve at the elbow. Because of the peripheral location, it was removed without damage to the underlying nerve.