Clinical meaning
Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment neuropathy, caused by compression of the median nerve as it passes through the carpal tunnel in the wrist. The carpal tunnel is a narrow, rigid passageway formed by the carpal bones on three sides and the transverse carpal ligament (flexor retinaculum) on the palmar side. Nine flexor tendons and the median nerve pass through this confined space.
When the contents of the tunnel swell or the tunnel narrows, the median nerve is compressed, causing ischemia and demyelination of the nerve fibers. The median nerve provides sensory innervation to the palmar surface of the thumb, index finger, middle finger, and the radial half of the ring finger, as well as motor innervation to the thenar muscles (thumb opposition and abduction). This anatomical distribution explains the characteristic symptom pattern.
Common causes include repetitive wrist movements (typing, assembly work), fluid retention (pregnancy, hypothyroidism, congestive heart failure), inflammatory conditions (rheumatoid arthritis), diabetes mellitus (increases nerve vulnerability to compression), and obesity. Women are three times more likely to develop CTS than men, partially because the carpal tunnel is typically smaller in women.
Symptoms typically begin with intermittent numbness and tingling in the median nerve distribution (thumb through radial ring finger), often worse at night because many people sleep with wrists flexed. As compression progresses, patients experience persistent numbness, weakness of grip and pinch strength, difficulty with fine motor tasks (buttoning clothes, holding small objects), and visible thenar muscle atrophy in advanced cases.