Peripheral Nerve Entrapment

An entrapment neuropathy is defined as a pressure-induced injury to a peripheral nerve in a segment of its course due to anatomic structures or pathologic processes. It occurs at anatomic sites where the nerve changes direction to enter a fibrous or osseofibrous tunnel, or where the nerve passes over a fibrous or muscular band. It occurs in these locations because of an increased risk of mechanical irritation.

Pathophysiology

Nerve entrapment can occur in tunnels, narrow anatomical spaces, fibrous bands, scar tissue, masses, bony calluses, external compression from casts or braces, oedema, and inflammation.

Prolonged compression causes ischaemia due to compression of vasa nervorum - the blood flow to the nerve itself. There is a mechanical deformation of the myelin sheath, and impairment of axonal transport of nutrients.

Clinical Features

The hallmarks are:

• Pain - burning, aching, tingling
• Paraesthesias with compression
• Tinel's sign - represents ectopic excitability
• "Double crush." This is a phenomenon where the clinical effect is greater than the sum of its parts. With the presence of a proximal lesion, the distal nerve is more vulnerable to being compromised. For example a patient with both a C6 lesion and a superficial radial nerve lesion will generally have a worse clinical picture than having either lesion alone.

Imaging

Under ultrasound nerve entrapment can be visualised by documenting nerve swelling, nerve compression, bone spurs with nerve path distortion, and external compression.

Literature Review

Literature Review

Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf

Articles from all years: PubMed search, Google Scholar search.

TRIP Database: clinical publications about evidence-based medicine.

Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,