Carpal tunnel syndrome (CTS) is an entrapment median neuropathy, causing paresthesia, pain, numbness, and other symptoms in the distribution of the median nerve due to its compression at the wrist in the carpal tunnel. The pathophysiology is not completely understood but can be considered compression of the median nerve traveling through the carpal tunnel. The National Center for Biotechnology Information and highly cited older literature say the most common cause of CTS is typing. More recent research by Lozano-Calderón has cited genetics as a larger factor than use, and has encouraged caution in ascribing causality.

The main symptom of CTS is intermittent numbness of the thumb, index, long and radial half of the ring finger. The numbness often occurs at night, with the hypothesis that the wrists are held flexed during sleep. Recent literature suggests that sleep positioning, such as sleeping on one’s side, might be an associated factor. It can be relieved by wearing a wrist splint that prevents flexion. Long-standing CTS leads to permanent nerve damage with constant numbness, atrophy of some of the muscles of the thenar eminence, and weakness of palmar abduction.

Pain in carpal tunnel syndrome is primarily numbness that is so intense that it wakes one from sleep. Pain in electrophysiologically verified CTS is associated with misinterpretation of nociception and depression.

Palliative treatments for CTS include use of night splints and corticosteroid injection. The only scientifically established disease modifying treatment is surgery to cut the transverse carpal ligament.

Patients with CTS experience numbness, tingling, or burning sensations in the thumb and fingers, in particular the index, middle fingers, and radial half of the ring fingers, which are innervated by the median nerve. Less-specific symptoms may include pain in the wrists or hands and loss of grip strength (both of which are more characteristic of painful conditions such as arthritis).

Some posit that median nerve symptoms can arise from compression at the level of the thoracic outlet or the area where the median nerve passes between the two heads of the pronator teres in the forearm., but this is highly debatable. This line of thinking is an attempt to explain pain and other symptoms not characteristic of carpal tunnel syndrome. Carpal tunnel syndrome is a common diagnosis with an objective, reliable, verifiable pathophysiology, whereas thoracic outlet syndrome and pronator syndrome are defined by a lack of verifiable pathophysiology and are usually applied in the context of nonspecific upper extremity pain.

Numbness and paresthesias in the median nerve distribution are the hallmark neuropathic symptoms (NS) of carpal tunnel entrapment syndrome. Weakness and atrophy of the thenar muscles may occur if the condition remains untreated.