Key Facts

CTS is the commonest peripheral nerve entrapment. Diagnosis is clinical, confirmed by NCS. Most patients respond to conservative or surgical treatment. Exclude underlying causes.

Epidemiology

Lifetime prevalence ~5-10%. Annual incidence ~3 per 1,000. F:M 3:1. Peak age 40-60 years. Bilateral in ~50%. Pregnancy-associated CTS: up to 50% (resolves postpartum in most).

Aetiology

• Idiopathic (most common): combination of anatomical and repetitive strain factors
• Conditions increasing carpal tunnel contents: flexor tenosynovitis (RA, overuse), ganglion cysts
• Conditions reducing carpal tunnel volume: fracture/dislocation (Colles, scaphoid)
• Systemic associations: pregnancy, hypothyroidism, diabetes mellitus, obesity, RA, acromegaly, amyloidosis (especially dialysis-related β2-microglobulin), gout

Pathophysiology

The carpal tunnel is a rigid space bounded by carpal bones and the flexor retinaculum. Increased pressure within the tunnel compresses the median nerve → ischaemia and demyelination (initially) → axonal degeneration (if prolonged/severe). Nocturnal symptoms relate to wrist flexion during sleep and increased interstitial fluid pressure at night.

Symptoms

• Pain and paraesthesiae: in median nerve distribution (thumb, index, middle, radial half of ring finger); often described as burning, tingling, numbness
• Nocturnal predominance: wakes patient from sleep; relieved by shaking or hanging hand over bed ("flick sign")
• Clumsiness: difficulty with fine motor tasks (buttons, holding objects)
• Radiation: pain may radiate to forearm, occasionally to upper arm/shoulder

Signs

• Sensory loss: in median nerve distribution (lateral 3½ digits palmar aspect)
• Thenar wasting: in advanced/severe disease (abductor pollicis brevis, opponens pollicis)
• Weakness of thumb abduction/opposition: late sign
• Tinel sign: tapping over carpal tunnel reproduces paraesthesiae (sensitivity ~50%)
• Phalen test: maximal wrist flexion for 60 seconds reproduces symptoms (sensitivity ~70%)
• Durkan test: direct compression over carpal tunnel for 30 seconds

Red Flags

• Thenar wasting (severe — needs urgent intervention)
• Bilateral CTS in young patient → think acromegaly, amyloidosis
• CTS + other neuropathies → systemic cause
• Post-traumatic CTS → acute carpal tunnel syndrome (surgical emergency)

Nerve Conduction Studies (Gold Standard)

• Median nerve sensory latency prolonged across wrist (>3.5 ms); reduced SNAP amplitude
• Median nerve motor latency prolonged (>4.2 ms to APB); reduced CMAP amplitude in severe
• Comparison with ulnar nerve latency increases sensitivity
• Sensitivity ~85-90%; specificity ~95%

Bloods (Screen for Underlying Cause)

• TFTs: hypothyroidism
• HbA1c: diabetes
• ESR/CRP, RF: rheumatoid arthritis
• U&Es: renal failure (dialysis-related amyloidosis)
• Pregnancy test: if appropriate

Imaging

• Wrist ultrasound: increased median nerve cross-sectional area at the wrist (>10 mm²); increasingly used as an adjunct
• MRI wrist: rarely needed; for space-occupying lesions or atypical cases
• X-ray wrist: if bony cause suspected (fracture, osteoarthritis)

Conservative (First-Line)

• Night wrist splint: neutral position; NICE CKS recommends as first-line; 4-6 weeks trial; effective in ~80% of mild-moderate cases
• Activity modification: avoid repetitive wrist flexion/extension, ergonomic assessment
• Corticosteroid injection: methylprednisolone 40 mg or triamcinolone 40 mg injected into carpal tunnel (ultrasound-guided improves accuracy); provides relief in ~70% but recurrence common (~50% at 1 year)

Surgical (Definitive)

• Carpal tunnel release (decompression): division of the flexor retinaculum; open or endoscopic approach
• Indications: failed conservative treatment, moderate-severe NCS findings, thenar wasting, constant numbness, acute CTS (post-trauma)
• Success rate ~90-95%; low complication rate
• NICE: refer for surgery if conservative management fails after 3-6 months, or if severe (thenar wasting, constant numbness)

Pregnancy-Related CTS

• Wrist splint first-line; most resolve postpartum within 3-6 months
• Avoid steroid injection if possible during pregnancy
• Surgery rarely needed

Referral Criteria

• Hand surgery/neurosurgery: failed conservative treatment, thenar wasting, severe NCS
• Neurology: diagnostic uncertainty, atypical features
• Endocrinology: if underlying hormonal cause identified

Mild CTS: ~30-40% resolve spontaneously. Splinting effective in ~80% of mild-moderate cases. Steroid injection: ~70% initial improvement; ~50% relapse within 1 year. Surgical decompression: ~90-95% success rate; most patients experience significant symptom relief within 6 weeks. Delayed treatment with thenar wasting may not fully recover muscle bulk. Pregnancy-related: ~90% resolve within 3-6 months postpartum.

Median Nerve — Key Anatomy

CTS Severity Grading (NCS)