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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Compression of the median nerve at the carpal tunnel — the most common peripheral nerve entrapment
- Symptoms: pain, numbness, tingling in the RADIAL 3½ digits (thumb, index, middle, radial half of ring finger). Worse at night
- Provocative tests: Tinel sign (tapping over carpal tunnel) and Phalen test (wrist flexion for 60 seconds)
- Nerve conduction studies confirm diagnosis: prolonged distal motor and sensory latencies
- Treatment: wrist splints (night), corticosteroid injection, surgical decompression (definitive)
Overview
Carpal tunnel syndrome (CTS) is caused by compression of the median nerve as it passes through the carpal tunnel at the wrist (between the carpal bones dorsally and the flexor retinaculum/transverse carpal ligament volarly). It is the most common entrapment neuropathy. The median nerve provides sensation to the palmar aspect of the radial 3½ digits and motor innervation to the thenar muscles (LOAF: Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis). Causes include idiopathic (most common), pregnancy, hypothyroidism, diabetes, rheumatoid arthritis, obesity, acromegaly, amyloidosis, and repetitive wrist use.
Epidemiology
CTS affects approximately 3–5% of the adult population. Female:male ratio is approximately 3:1. Peak incidence is 40–60 years. It is extremely common in pregnancy (hormone-mediated fluid retention). Bilateral in ~50% of cases. Occupational risk factors include repetitive wrist movements, vibrating tools, and sustained wrist flexion/extension.
Clinical Features
Symptoms
Pain, numbness, and tingling in the median nerve distribution: thumb, index, middle, and radial half of ring finger
Symptoms worse at NIGHT — waking from sleep with hand numbness and need to shake/flick hand ("flick sign")
Weakness of grip and clumsiness: dropping objects, difficulty with fine motor tasks (buttons, keys)
Symptoms may radiate to forearm
Signs
Tinel sign: tapping over the carpal tunnel at the wrist reproduces paraesthesiae (sensitivity ~50%)
Phalen test: sustained wrist flexion for 60 seconds reproduces symptoms (sensitivity ~70%)
Reduced sensation in median nerve distribution (test light touch and two-point discrimination)
Thenar muscle wasting (APB) — LATE sign indicating chronic severe compression
Weakness of thumb abduction (abductor pollicis brevis)
Investigations
First-line
Nerve conduction studies (NCS)Confirmatory test. Prolonged distal sensory latency and distal motor latency of median nerve across the carpal tunnel. Required before surgical decompression
Second-line
BloodsTFTs (hypothyroidism), glucose/HbA1c (diabetes), ESR/CRP and RF (RA) — to identify underlying cause
Ultrasound of carpal tunnelMay show swollen median nerve (cross-sectional area >10 mm² at pisiform level). Increasingly used as initial assessment
Specialist
Clinical diagnosisIn typical presentations with classic symptoms and positive provocative tests, NCS may not be needed before a trial of conservative management
Management
NICE CKS — Carpal tunnel syndrome1
Conservative (first-line)
- Night-time wrist splint in neutral position — worn for ≥4 weeks. Prevents wrist flexion during sleep
- Lifestyle modifications: ergonomic assessment, avoid sustained wrist flexion/extension
- Pregnancy-related CTS usually resolves after delivery — conservative management preferred
2
Corticosteroid injection
- Local corticosteroid injection into the carpal tunnel — effective for temporary relief (weeks-months)
- Can be repeated but not a long-term solution
3
Surgical decompression (definitive)
- Carpal tunnel decompression (open or endoscopic): division of the flexor retinaculum
- Indicated if: conservative management fails, progressive symptoms, thenar wasting, severe NCS findings
- Cure rate: ~90%. Full recovery of sensation may take months
Complications
- Permanent median nerve damage: If chronic severe compression — irreversible thenar wasting and sensory loss
- Recurrence: ~5% after surgical decompression
- Surgical complications: Incomplete release, wound infection, nerve injury, pillar pain (rare)
UKMLA Exam Tips
- 1Median nerve: LOAF muscles (Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis)
- 2Sensation: palmar radial 3½ digits (thumb, index, middle, radial half of ring)
- 3Worse at NIGHT is characteristic — flick sign (patient shakes/flicks hand to relieve symptoms)
- 4Thenar wasting = LATE sign — do not wait for this before referring
- 5In pregnancy: usually resolves post-delivery — conservative management
- 6Causes: pregnancy, hypothyroidism, diabetes, RA, acromegaly, obesity, idiopathic
- 7NCS: prolonged distal motor and sensory latencies of median nerve across carpal tunnel
practicetest your knowledge on carpal tunnel syndromeApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — musculoskeletal and beyond.
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