Cubital Tunnel Syndrome
(See also Overview and Evaluation of Hand Disorders.)
The ulnar nerve is commonly irritated at the elbow or, rarely, the wrist. Cubital tunnel syndrome is most often caused by leaning on the elbow or by prolonged and excessive elbow flexion. It is less common than carpal tunnel syndrome. Baseball pitching (particularly sliders), which can injure the medial elbow ligaments, confers risk.
Symptoms of cubital tunnel syndrome include numbness and paresthesia along the ulnar nerve distribution (in the ring and little fingers and the ulnar aspect of the hand) and elbow pain. In advanced stages, weakness of the intrinsic muscles of the hand and the flexors of the ring and little fingers may develop. Weakness interferes with pinch between the thumb and index finger and with hand grip. Patients with chronic cubital tunnel syndrome may present with an ulnar claw hand. An ulnar claw hand is metacarpophalangeal joint extension and interphalangeal joint flexion of the small and ring fingers caused by an imbalance between intrinsic and extrinsic hand muscles.
Diagnosis of cubital tunnel syndrome is often possible clinically. However, if clinical diagnosis is equivocal and when surgery is being considered, nerve conduction studies are done. Cubital tunnel syndrome is differentiated from ulnar nerve entrapment at the wrist (in Guyon canal) by the presence of sensory deficits over the ulnar dorsal hand, by the presence of ulnar nerve deficits proximal to the wrist on muscle testing or nerve conduction velocity testing, and by the elicitation of ulnar hand paresthesias by tapping the ulnar nerve in the cubital tunnel at the elbow (positive Tinel sign). Cubital tunnel syndrome may be confused with proximal nerve compression such as that caused by thoracic outlet syndrome (TOS) or C8-T1 cervical radiculopathy (see table Motor and Reflex Effects of Spinal Cord Dysfunction by Segmental Level).