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Decision Making in Upper Extremity Entrapment Neuropathies

Decision Making in Upper Extremity Entrapment Neuropathies

ABSTRACT: Entrapment of the median, ulnar, and radial nerves in the upper extremity leads to a variety of syndromes. Physicians should have a thorough understanding of the causes, anatomy, diagnosis, and treatment options to provide patients with information for making effective decisions. The patient's occupational and recreational activities and comorbid medical conditions should be considered. The primary causative factor is mechanical compression of the nerve. Patient evaluation should start with a thorough history and physical examination, which may involve sensibility, provocative, and muscle strength testing. Diagnostic imaging and electrodiagnostic studies may help. A simple classification of nerve entrapment lesions separates patients who are candidates for a trial of conservative therapy from those who will require referral for surgery. (J Musculoskel Med. 2008;25:278-289)

Entrapment neuropathies are common, especially in the upper extremity, and may result in significant disability and morbidity. Entrapment of the median, ulnar, and radial nerves leads to a variety of syndromes. Patients may present with sensory disturbances of numbness, tingling, and pain in the distribution of the compressed nerve and motor dysfunction in the muscles supplied by the nerve. Pure pain, sensory, or motor syndromes or mixed syndromes may occur, depending on which nerve is affected.

The treating physician should have a thorough understanding of the causes, anatomy, and diagnosis of entrapment neuropathies, as well as the treatment options, to provide patients with the information needed to make the best decisions in managing their condition. Many factors play a role in the decision-making process; the patient's occupational and recreational activities and comorbid medical conditions should be considered, because they may affect the genesis or aggravation of nerve compression syndromes. Patients should be made aware of the natural history of their condition, especially if permanent neurological damage is a possibility when the condition is left unmanaged. In this article,we discuss the important decision-making factors.

PATHOPHYSIOLOGY

The primary causative factor in entrapment neuropathy is mechanical compression of the nerve. Normal anatomical structures along the nerve's path may be the source of compression (Table).

Table

Potential sources of entrapment include a space with limited compliance, such as the carpal tunnel; proximity of the nerve to fibrous tendinous arches; and fascial bands. The nerve may be directly compressed along its course by abnormal anatomy that results from fractures, synovitis from rheumatoid arthritis, ganglion cysts, tumors, osteophytes, or aberrant muscles.

Chronic compression of the nerve leads to a pathological process that starts with obstruction of venous return. This process leads to segmental anoxia, capillary vasodilatation, and endoneurial edema, which compounds the compressive effects and leads to a disruption in axonal and cellular exchange.1 With prolonged compression, intraneural fibrosis and demyelination of nerve fibers begins; ultimately, it results in axonal degeneration. When the nerve cannot glide normally in its path, additional internal compression results from traction on the nerve.

Compression along the nerve may occur in more than 1 location (the "double-crush"phenomenon).2 Compression in a proximal location may disrupt axonal transport of nutrients essential for the survival and normal functioning of the axon, increasing the susceptibility of the distal axon to the effects of compression. For example, nerve compression in the cervical spine may increase the patient's propensity for carpal tunnel syndrome (CTS).

 

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