Define Carpal Tunnel Syndrome. Describe its clinical features, investigations and management.

Definition

Carpal tunnel syndrome (CTS) is the commonest entrapment neuropathy, caused by compression of the median nerve as it passes through the carpal tunnel at the wrist — the space bounded by the carpal bones and roofed by the flexor retinaculum (transverse carpal ligament). Anything that reduces the volume of the tunnel or increases its contents raises the pressure on the nerve.

The median nerve is compressed within the carpal tunnel beneath the flexor retinaculum.

Causes & Risk Factors

Often idiopathic, but recognised associations include pregnancy, hypothyroidism, rheumatoid arthritis, diabetes, acromegaly, obesity, repetitive wrist use, and local causes (fractures, ganglia, tenosynovitis). It is commoner in middle-aged women.

Clinical Features

Tingling, numbness and pain in the median nerve distribution (thumb, index, middle and radial half of the ring finger), classically worse at night and relieved by shaking the hand. Advanced disease causes weakness and wasting of the thenar muscles (abductor pollicis brevis) and clumsiness. Tinel’s sign (tapping over the nerve) and Phalen’s test (sustained wrist flexion) reproduce the symptoms.

Investigations

The diagnosis is largely clinical; nerve conduction studies confirm and grade median nerve slowing at the wrist and are useful before surgery or in atypical cases. Investigate for underlying causes (thyroid function, glucose) where indicated.

Management

Conservative treatment suits mild/intermittent symptoms: night wrist splints (in neutral), activity modification, treatment of any underlying cause, and corticosteroid injection into the carpal tunnel. Surgical decompression — division of the flexor retinaculum (‘carpal tunnel release’, open or endoscopic) — is indicated for persistent or severe symptoms or when there is thenar wasting / motor loss, and gives reliable relief.

Complications & Differential Diagnosis

Untreated or severe carpal tunnel syndrome leads to permanent thenar wasting and weakness of opposition, with incomplete recovery even after decompression, so timely surgery in the presence of motor signs matters. The main differentials are a cervical radiculopathy (C6/C7), a more proximal median-nerve entrapment (pronator syndrome), and a generalised peripheral neuropathy — distinguished by the distribution of symptoms, associated neck or systemic features, and nerve conduction studies. Surgical complications of release include incomplete division, scar tenderness (‘pillar pain’) and, rarely, injury to the palmar cutaneous or recurrent motor branch.

• Commonest entrapment neuropathy: median nerve compressed under the flexor retinaculum.
• Associations: idiopathic, pregnancy, hypothyroidism, RA, diabetes, repetitive use.
• Night tingling in thumb–radial ring finger (spares little finger); thenar wasting late.
• Tinel’s & Phalen’s reproduce symptoms; NCS confirm.
• Splint/steroid injection for mild; carpal tunnel release for severe or thenar wasting.