Disease involving the ulnar nerve from its origin in the brachial plexus to its termination in the hand. Clinical manifestations may include paresis or paralysis of wrist flexion, finger flexion, thumb adduction, finger abduction, and finger adduction. Sensation over the medial palm, fifth finger, and ulnar aspect of the ring finger may also be impaired. Common sites of injury include the axilla, cubital tunnel at the elbow, and Guyon's canal at the wrist. (From Joynt, Clinical Neurology, 1995, Ch51 pp43-5)