Nerve Entrapment Syndromes

Updated: Sep 21, 2017
  • Author: Amgad Saddik Hanna, MD; Chief Editor: Brian H Kopell, MD  more...
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Overview

Practice Essentials

Entrapment neuropathies are a group of disorders of the peripheral nerves that are characterized by pain and/or loss of function (motor and/or sensory) of the nerves as a result of chronic compression.

The brain and spinal cord receive and send information through muscles and sensory receptors, and the information sent to organs is transmitted through nerves. The nerves travel to the upper and lower extremities and traverse the various joints along their paths. Unfortunately, these nerves can become compressed or entrapped at various regions of the extremities, especially at "tunnel" regions, where they may be predisposed or vulnerable to compression.

Neurosurgeons, among other surgical specialists (eg, orthopedists and plastic surgeones), treat these entrapment neuropathies, which can account for 10-20% of the practice’s cases. The first operations or decompressions for different nerve entrapments were performed more than a century ago, but the disorders were described even earlier by such pioneering physicians as Sir Astley Cooper (1820s) and Sir James Paget (1850s).

Carpal tunnel syndrome (CTS), compression of the median nerve at the wrist, is the most common entrapment neuropathy. Cubital tunnel syndrome is the second most common and is caused by a compression at the elbow. [1] Other rare nerve entrapment syndromes include the suprascapular nerve, which accounts for approximately 0.4% of upper girdle pain symptoms, and meralgia paresthetica, which is a compression of the lateral femoral cutaneous nerve [LFCN] in the groin. [2]

An ulnar nerve transposed at the elbow is shown in the image below.

Ulnar nerve (U) transposition at the elbow. A: The Ulnar nerve (U) transposition at the elbow. A: The medial intermuscular septum (arrows) is resected to prevent compression of the transposed nerve. Vasoloops are around the ulnar nerve and a vascular pedicle between the nerve and the septum that has been preserved. B: After subcutaneous transposition, the ulnar nerve is observed lax in elbow flexion. The ulnar nerve and its distal branches are surrounded by vasoloops.

This article summarizes some basic principles of entrapment neuropathies, and, within each section, the specifics of the most common entrapment syndromes are outlined. Together, this information should provide the reader with a solid basis for further investigation.

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Etiology

Nerve entrapment syndromes result from chronic injury to a nerve as it travels through an osseoligamentous tunnel; the compression is typically between the ligamentous canal and bony surfaces. Other potential anatomical sites for entrapment include the muscular arcade of the supinator (also known as the arcade of Frohse), the posterior interosseous nerve (PIN), and the thoracic outlet for the lower trunk of the brachial plexus. [3]

In cases of nerve entrapment, at least one portion of the compressive surfaces is mobile. This results in either a repetitive "slapping" insult or a "rubbing/sliding" compression against sharp, tight edges, with motion at the adjacent joint that results in a chronic injury. Immobilization of the nerve with a splint or lifestyle adjustments may therefore resolve the symptoms. Entrapment neuropathies can also be caused by systemic disorders, such as rheumatoid arthritis, pregnancy, acromegaly, or hypothyroidism.

Suprascapular nerve entrapment may cause 2% of all cases of chronic shoulder pain. Of the many reported causes of suprascapular nerve entrapment, the most common are para-labral cysts, usually in the spinoglenoid notch, and microtrauma in elite athletes. [4]

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Pathophysiology

Repetitive injury and trauma to a nerve may result in microvascular (ischemic) changes, edema, injury to the outside layers of the nerve (myelin sheath) that aid in the transmission of the nerve’s messages, and structural alterations in membranes at the organelle levels in both the myelin sheath and the nerve axon. Focal segmental demyelination at the area of compression is a common feature of compression syndromes. Complete recovery of function after surgical decompression reflects remyelination of the injured nerve. Incomplete recovery in more chronic and severe cases of entrapment is due to Wallerian degeneration of the axons and permanent fibrotic changes in the neuromuscular junction that may prevent full reinnervation and restoration of function.

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Indications

See Medical therapy and Intraoperative details.

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