Peripheral compression lesions of the ulnar nerve.

ANATOMY The anatomical course of the ulnar nerve renders it particularly vulnerable at the elbow and at the wrist. At both sites the nerve or its terminal branches pass through narrow canals in which small space-occupying lesions may exert pressure. As the nerve crosses the elbow it passes from the extensor aspect of the arm into the flexor mass of the forearm, running between the two heads of origin of the flexor carpi ulnaris