Median Nerve Block at the Wrist for Carpal Tunnel Syndrome

Indications and Clinical Considerations

Median nerve block at the wrist is primarily used in managing carpal tunnel syndrome. Carpal tunnel syndrome is caused by compression of the median nerve as it passes through the carpal canal at the wrist ( Figs. 81.1 and 81.2 ). The most common causes of compression of the median nerve at this anatomic location include flexor tenosynovitis, rheumatoid arthritis, pregnancy, amyloidosis, and other space-occupying lesions including a persistent median artery that compromises the median nerve as it passes through this closed space ( Fig. 81.3 ). Other conditions associated with carpal tunnel syndrome are listed in Box 81.1 . This entrapment neuropathy manifests as pain, numbness, paresthesias, and associated weakness in the hand and wrist that radiates to the thumb, the index and middle fingers, and the radial half of the ring finger. These symptoms also may radiate proximal to the entrapment into the forearm. If the condition is not treated, progressive motor deficit and, ultimately, flexion contracture of the affected fingers can result. The onset of symptoms usually occurs after repetitive wrist motions or from repeated pressure on the wrist, as occurs when resting the wrists on the edge of a computer keyboard. Direct trauma to the median nerve as it enters the carpal tunnel also may result in a similar clinical presentation.