Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is compression of the median nerve at the wrist, and it is the commonest entrapment neuropathy.

It is more common in women and from middle age. Risk factors include pregnancy, obesity, diabetes, hypothyroidism, rheumatoid arthritis and repetitive forceful wrist use. Most cases are idiopathic and respond to conservative care, but persistent or progressive compression can cause permanent sensory and motor loss.

The carpal tunnel is bounded by the carpal bones dorsally and the flexor retinaculum (transverse carpal ligament) volarly. It carries the median nerve and 9 flexor tendons (4 FDS, 4 FDP and FPL), so any loss of space or increase in contents compresses the nerve.

Sustained pressure reduces blood flow within the nerve and causes focal demyelination, with axonal loss later. Pressure rises with wrist flexion and extension, which explains night-time and position-provoked symptoms. The recurrent motor branch supplies the thenar muscles and is the first motor casualty.