The etiology of Carpal Tunnel Syndrome

by Noluthando Magubane

Carpal tunnel syndrome (CTS) is the most common median nerve neuropathy that was first described by Paget in 1854. It is a medical condition caused by damage to the median nerve due to compression and traction of the nerve at the level of the carpal tunnel. This condition affects 4-5% of the population and is most prevalent in females around the ages of 40-60 but males are also susceptible to this condition (average age of 45-60). It is characterised by pain, numbness or a tingling sensation in the affected hand and arm.

The carpal tunnel is an osteofibrous outlet lying between the transverse carpal ligament (the intermediate part of a fibrous connective tissue band called the flexor retinaculum) which forms the roof, and the carpal bones that form the floor of the tunnel. Entering through the tunnel are nine flexor tendons and the median nerve. The median nerve enters the tunnel through the midline of or slightly radial (closer to the thumb) and innervates the first three radial digits and the radial half of the 4th digit, it also gives off a palmer sensory cutaneous branch which innervates the cutaneous skin of the palm these are the areas affected in CTS.

The pathophysiology of carpal tunnel syndrome involves an increased pressure within the carpal tunnel that decreases the function of the median nerve. Conditions that lead to compression of the carpal tunnel and hinders mobility, create lesions on the median nerve when the wrist is moved. Hypertrophy of the synovial tissue of the flexor tendons is a possible cause, in this condition constructive scar tissue is formed around the median nerve compressing it and increasing the pressure around the nerve resulting in tearing. The issue causing CTS could also originate at the nerve itself when the connective tissue surround the nerve becomes stiff. The purpose of this connective tissue is for the nerve to be extendable and not become injured when the wrist is moved. The stiffness exposes the nerve to shearing forces that could harm the nerve.

Risk factors associated with CTS can be medical or occupational. Medical factors include extrinsic factors such a fracture in the distal radius that increase the volume of the synovial sheath within the tunnel, intrinsic factors where tumours form in the tunnel increasing the occupied volume and neuropathic factors such as diabetes or alcoholism that can affect the function of the median nerve. Occupational risk factors involve any repetitive wrist movement or repetitive tasks such as typing. CTS can be treated by resting the affected hand and surgical interventions are also possible.

Reference

Aboonq, M. (2015) Pathophysiology of carpal tunnel syndrome. Neurosciences. 20 (1), 4–9.

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