The cubital tunnel syndrome is caused by entrapment (compression) of the ulnar nerve in the cubital tunnel. This tunnel runs from the inside of the upper arm through the groove behind the elbow bone (” funny bone”) to the inside of the middle of the forearm. it may be caused by a previous injury (fracture, dislocation), osteoarthritis of the elbow joint or chronic pressure on the nerve. This maybe the result of constant pressure when the arm is lying on a desk at work or is bent for hours when asleep. In most cases, however, there is no obvious reason for the mostly sudden onset of symptoms.
Typical symptoms are tingling (needles and pins), numbness and loss of sensation of the tip of the small finger, the ulnar half of the ringfinger and the back of the hand on the ring and samll finger side. Chronic nerve compression leads to weakness of grip and later palsy of the muscles that are innervated by the ulnar nerve. Due to loss of pinch strength writing with a pen becomes difficult and spreading the fingers becomes weak or impossible. The first sign of muscle involvement maybe that the small finger can no longer be pressed against the ring finger and is standing slightly apart. Later wasting (atrophy) of the muscles occurs, most ovbvioous between thumb and index finger. The pain may radiate from the elbow to small and ring finger. The diagnosis is usually confirmed by electrical testing of nerve.