Upper limb nerve entrapment syndromes

Abstract

The median nerve is formed by contributions from the lateral and medial cords of the brachial plexus. Signs and symptoms of a median neuropathy include dysesthesias of the first four fingers in a median distribution, hand pain, and thumb weakness, or atrophy of the thenar eminence. Median nerve compression at the wrist, or carpal tunnel syndrome, is the most common nerve entrapment syndrome. Pregnancy and hormonal factors may contribute to median nerve compression in the female wrist. The second most common nerve compression site is the ulnar nerve at the cubital tunnel. Anywhere from 3 to 20 mm after the ulnar groove, the nerve runs in the cubital tunnel, formed beneath the two heads of the flexor carpi ulnaris muscle. Signs and symptoms consistent with ulnar neuropathy include intrinsic hand muscle weakness resulting in loss of dexterity and grip strength. Sensory symptoms are not as prominent as motor symptoms in an ulnar neuropathy. If present, the area affected will be the dorsal fifth and medial fourth digits as well as the medial hand. Typically, males have a higher prevalence of ulnar neuropathy than females. The posterior cord of the brachial plexus gives off the axillary, thoracodorsal, and subscapular nerves before terminating as the radial nerve. Radial neuropathy at the spiral groove will present as wrist- and finger-drop but spares elbow extension since the muscular branches to the triceps brachii and anconeus muscles arise proximally to the spiral groove. In a superficial radial sensory neuropathy, there will be sensory disturbance of the lateral dorsal hand and thumb plus the dorsal proximal phalanges of digits 2, 3, and 4. The suprascapular nerve comes off the upper trunk of the brachial plexus proximally and contains C5 and C6 innervation. The nerve runs posteriorly under the trapezius and travels through the suprascapular notch of the scapula into the supraspinous fossa to innervate the supraspinatus muscle. Volleyball, tennis, dancing, painting, pitching, and other overhand throwing are activities that have been associated with suprascapular neuropathy. There is no known gender association. Traumatic injuries to the brachial plexus are the most common etiology of brachial plexopathies. Breast cancer, lymphomas, and lung cancer are the most frequent cause of lymphadenopathy causing plexopathy. Radiation treatment protocols often include the region of the brachial plexus, especially for treatment of lymphomas and breast, lung, and neck cancers. Idiopathic brachial plexopathy is more common in males. Nonneoplastic mass effects may occur, such as hematomas from internal jugular catheters or vascular abnormalities like arteriovenous malformations or aneurysms.