Nerve Entrapment

1. Definition / description

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.

2. Epidemiology / 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.

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.

3. 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.

4. Symptoms

1. Pain
   # Paresthesia
   # Burning sensation
   # Tingling sensation
   # Impaired movement of affected body part
   # Numbness
   # Muscle weakness
   # Muscle wasting
   # Dry thin skin - chronic cases of motor and sensory nerve entrapment
        

5. Examination

In the medical examination the doctor attempt to produce the discomfort symptoms by scratching or pushing the area in which the nerve is entrapped. By administering a couple of millilitres of local anaesthetic in this area the symptoms should disappear if the diagnosis is correct (otherwise the diagnosis is wrong). There is no examination (X-ray, ultrasound, MRI, scintigraphy) that can detect the nerve entrapment. The real frequency of the diagnosis is debated amongst professionals.

6. Treatment

Since the condition is harmless and without risk even if you continue sports activity, continuing sport is recommended in the hope that the discomfort will pass on its own. Pausing and alternative training of the abdominal muscles can be attempted. If the discomfort is long-lasting with no sign of abatement, even during summer or winter breaks, you can consider surgically severing the nerve, provided that pain abates when local anaesthesia is administered (article-1) (article-2).

Related articles

http://solvimax2012.mmc.nl/content/download/76427/609795/file/Surgery%20article%202010.pdf  

http://www.slideshare.net/drferzli/anatomy-related-etiologygroinpain

References

Nerve Compression Syndromes: Diagnosis and Treatment, Robert M. Szabo, 5 August 2008