Carpal tunnel syndrome: Etiology and epidemiology
- Milind J Kothari, DO
Milind J Kothari, DO
- Professor of Neurology
- Penn State College of Medicine
Carpal tunnel syndrome (CTS) refers to the complex of symptoms and signs brought on by compression of the median nerve as it travels through the carpal tunnel. Patients commonly experience pain, paresthesia, and less commonly, weakness in the median nerve distribution. CTS is the most frequent compressive focal mononeuropathy seen in clinical practice.
This topic will review the etiology of CTS. Other clinical aspects of CTS are discussed separately. (See "Carpal tunnel syndrome: Clinical manifestations and diagnosis" and "Carpal tunnel syndrome: Treatment and prognosis".)
The carpal tunnel is formed by the transverse carpal ligament (flexor retinaculum) superiorly with the carpal bones inferiorly (figure 1) . The median nerve, accompanied by the nine flexor tendons of the forearm musculature, must pass through this anatomic tunnel (figure 2) [1-3]. When compression of the median nerve occurs, ischemia and mechanical disruption of the nerve follow.
The median nerve emerges from the brachial plexus in the upper arm with contributions from the C6, C7, C8, and T1 nerve roots (figure 3). Roots C6 and C7 supply the median sensory fibers that provide sensation to the thenar eminence and the first three and a half digits of the hand. Roots C8 and T1 supply the motor fibers to the muscles of the forearm and hand that are innervated by the median nerve. Thus, nerve fibers that are destined to comprise the median nerve exit the spine at these nerve roots to travel in the upper, middle, and lower trunks of the brachial plexus. These fibers will then pass through the lateral and medial cords of the brachial plexus and combine to form the median nerve.
The median nerve has no branches in the upper arm. As the median nerve passes through the antecubital fossa region, it lies adjacent to the brachial artery on the medial side before passing more deeply within the forearm.
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