Carpal Tunnel Anatomy, Causes, Symptoms and Special Tests

Ian describes the tunnel as carpal bones beneath the transverse carpal ligament, containing the flexor tendons, synovium, blood vessels and median nerve. Problems with the wall include wrist dislocation and distal radius malunion, while problems with the contents include tenosynovitis, infection, rheumatoid arthritis, pregnancy, hypothyroidism, kidney failure, cysts and tumors. Obesity matters through diabetes, collagen turnover and wrist circumference. Repetitive motion and vibration raise pressure and impair microcirculation, setting off a cascade of edema, nerve dysfunction and inflammation. Sensory fibers are usually affected before motor fibers, and autonomic changes can occur. Causes are multifactorial: genetics, repetitive or vibrating work, sudden increases in computer use, obesity, systemic disease and pregnancy. Symptoms include numbness, tingling and aching, often worse at night, with weakness of the thumb, index and middle fingers and atrophy of the thenar eminence and first two lumbricals in later stages. The hand elevation test has the best clinical utility, followed by the Durkan, Phalen and Tinel tests. The upper limb tension test 1 is less accurate for diagnosis but useful for assessing nerve mobility.