Ulnar Tunnel Syndrome

Ulnar tunnel syndrome causes numbness and tingling in the little finger and along the outside of the ring finger. Ulnar tunnel syndrome is not usually caused by repetitive motions.

Cause

Distal ulnar tunnel showing the three zones of entrapment. Lesions in zone 1 cause both motor and sensory symptoms. Lesions in zone 2 cause motor deficits. Lesions in zone 3 create sensory deficits.

The ulnar nerve is one of three major nerves that provide feeling and function to the hand. The ulnar nerve runs down the inside of the forearm to the heel of the hand. There, it branches out across the palm and into the little and ring fingers. Excessive pressure on this nerve can cause a loss of feeling and/or muscle weakness in the hand.

Symptoms
Symptoms develop gradually. Weakness and increasing numbness, particularly on the little finger side of the hand are usual signs of ulnar tunnel syndrome. The degree of weakness and numbness depends on the location of the pressure point. Pain may or may not be present. As the syndrome progresses, it may become more difficult to open jars, hold objects, or coordinate the fingers during such tasks as typing or playing a musical instrument.

The arrow shows an area of muscle wasting that suggests ulnar nerve entrapment at the wrist.
Courtesy of Griffin LY (ed): Essentials of Musculoskeletal Care. 3rd Ed. Rosemont, IL. American Academy of Orthopaedic Surgeons, 2005
The hand is examined for signs that the muscle is wasting (atrophy) or weakness and dry skin in the spaces between the fingers. One test involves tapping a finger over the ulnar nerve to determine whether this causes a tingling sensation (Tinel sign). X-rays may be used to identify whether a fragment of a fractured bone is pressing on the nerve.

Because the ulnar nerve also travels through a narrow tunnel at the elbow, that area is examined as well. Pressure at that point in the elbow can cause symptoms in the hand.