The Median Nerve at the Carpal Tunnel … and Elsewhere

Abstract

The median nerve (MN) may be affected by various peripheral neuropathies, each of which may be categorized according to its cause, as either an extrinsic (due to an entrapment or a nerve compression) or an intrinsic (including neurogenic tumors) neuropathy. Entrapment neuropathies are characterized by alterations of the nerve function that are caused by mechanical or dynamic compression. It occurs because of anatomic constraints at specific locations including sites where the nerve courses through fibro-osseous or fibromuscular tunnels or penetrates a muscle. For the diagnosis of peripheral neuropathies, physicians traditionally relied primarily on clinical findings and electrodiagnostic testing with electromyography. However, if further doubt exists, clinicians may ask for an additional imaging evaluation.

Potential compression of the musculocutaneous, median and ulnar nerves by a very rare variant of the coracobrachialis longus muscle

“…MN compression can occur at various sites along its course [2,33]. The most common type of MN neuropathy is carpal tunnel syndrome [11,33].…”

Magnetic resonance imaging of the wrist and hand

“…The ulnar margin consists of the hook of the hamate, triquetrum, and pisiform bones. The radial margin of the carpal tunnel consists of the scaphoid, trapezium, and the flexor carpi radialis tendon sheath [ 26 , 35 ].…”

Normal variations in position and relations of the median nerve in the carpal tunnel: A cross‐sectional observational study using clinical magnetic resonance imaging

“…If this is the case, then other factors, including the shape of the carpal tunnel and the motion and loads applied to it, are likely also to be part of any phenotype that might predispose to a median neuropathy. The etiology of CTS is not yet fully understood, but complex mechanisms involving both compression and traction of the median nerve have been proposed (Garland et al ; Horch et al ; Meyer et al ).…”

“…It may be that a particular position within the tunnel or a relation to a particular tendon, or a combination of these two factors, predisposes to conditions such as carpal tunnel syndrome (CTS). The etiology of CTS is complex and multifactorial; however, there is some evidence to suggest that the dynamic relationship between the position of the median nerve and the adjacent tendons and also variations in wrist position may give rise to combinations of compressive and traction forces that lead to compromise of the median nerve (Garland et al ; Zeiss et al ; Skie et al ; Horch et al ; Kunze et al ; Goetz et al ; Meyer et al ). It may be that variations in median nerve position, before dynamic changes in relationships with adjacent tendons, predispose to CTS.…”