Abstract
Ulnar nerve entrapment at the elbow is one of the most common entrapment neuropathies encountered in clinical practice. Causes include compression of the ulnar nerve by an aponeurotic band that runs from the medial epicondyle of the humerus to the medial border of the olecranon, direct trauma to the ulnar nerve at the elbow, and repetitive elbow motion. Ulnar nerve entrapment at the elbow is also called tardy ulnar palsy, cubital tunnel syndrome, and ulnar nerve neuritis. This entrapment neuropathy manifests as pain and associated paresthesias in the lateral forearm that radiate to the wrist and to the ring and little fingers. Some patients also notice pain referred to the medial aspect of the scapula on the affected side. Untreated, ulnar nerve entrapment at the elbow can result in a progressive motor deficit and, ultimately, flexion contracture of the affected fingers. Symptoms usually begin after repetitive elbow motion or repeated pressure on the elbow, such as leaning on the elbow while lying on the floor. Direct trauma to the ulnar nerve as it enters the cubital tunnel may result in a similar clinical presentation. Patients vulnerable to nerve syndromes, such as diabetic and alcoholic patients, are at greater risk for the development of ulnar nerve entrapment at the elbow.
Keywords
ulnar nerve entrapment, ulnar nerve, compression neuropathies, parethesias, ulnar nerve block, ultrasound guided procedures, tardy ulnar palsy, diagnostic ultrasonography, flexion contracture
ICD-10 CODE G65.20
The Clinical Syndrome
Ulnar nerve entrapment at the elbow is one of the most common entrapment neuropathies encountered in clinical practice. Causes include compression of the ulnar nerve by an aponeurotic band that runs from the medial epicondyle of the humerus to the medial border of the olecranon, direct trauma to the ulnar nerve at the elbow, and repetitive elbow motion. Ulnar nerve entrapment at the elbow is also called tardy ulnar palsy, cubital tunnel syndrome, and ulnar nerve neuritis. This entrapment neuropathy manifests as pain and associated paresthesias in the lateral forearm that radiate to the wrist and to the ring and little fingers. Some patients also notice pain referred to the medial aspect of the scapula on the affected side. Untreated, ulnar nerve entrapment at the elbow can result in a progressive motor deficit and, ultimately, flexion contracture of the affected fingers. Symptoms usually begin after repetitive elbow motion or repeated pressure on the elbow, such as leaning on the elbow while lying on the floor ( Fig. 45.1 ). Direct trauma to the ulnar nerve as it enters the cubital tunnel may result in a similar clinical presentation. Patients vulnerable to nerve syndromes, such as diabetic and alcoholic patients, are at greater risk for the development of ulnar nerve entrapment at the elbow.
Signs and Symptoms
Physical findings include tenderness over the ulnar nerve at the elbow. A positive Tinel sign is usually present over the ulnar nerve as it passes beneath the aponeurosis. Weakness of the intrinsic muscles of the forearm and hand that are innervated by the ulnar nerve may be identified with careful manual muscle testing; however, early in the course of cubital tunnel syndrome, the only physical finding other than tenderness over the nerve may be loss of sensation on the ulnar side of the little finger. Muscle wasting of the intrinsic muscles of the hand can best be identified by viewing the hand from above with the palm down. Patients suffering from ulnar nerve entrapment at the elbow often exhibit a positive Froment sign, which is owing to weakness of the adductor pollicis brevis and flexor pollicis brevis muscles ( Fig. 45.2A ). Patients with significant muscle weakness secondary to ulnar nerve entrapment at the elbow also exhibit a positive Wartenberg sign, with patients often complaining that the little finger gets caught outside the pants pocket when they reach for car keys ( Fig. 45.2B ). Patients suffering from ulnar nerve entrapment at the elbow may also exhibit a positive little finger adduction test ( Fig. 45.2C ).
