Carpal Tunnel Syndrome
Compression neuropathy of the median nerve at the wrist, causing pain, paraesthesiae, and weakness in the median nerve distribution. Most common peripheral nerve entrapment. Treated with splinting, injection, or surgical decompression.
Key Facts
Most common peripheral nerve entrapment: lifetime prevalence ~3–6% Median nerve compressed in the carpal tunnel at the wrist Symptoms: nocturnal paraesthesiae in thumb, index, middle, and radial half of ring finger; relieved by shaking hand (flick sign) Risk factors: pregnancy (~50% in 3rd trimester), diabetes, hypothyroidism, RA, obesity, repetitive wrist use, acromegaly Tests: Tinel sign (tapping carpal tunnel reproduces symptoms), Phalen sign (wrist flexion × 60 seconds) Nerve conduction studies: gold standard; confirms diagnosis and severity Treatment: night splints (wrist in neutral), corticosteroid injection (triamcinolone 40mg), surgical decompression for persistent/severe cases NICE: carpal tunnel decompression is one of the most common elective surgical procedures in the UK
Overview
Key Facts
Carpal tunnel syndrome (CTS) is the most common peripheral entrapment neuropathy, caused by compression of the median nerve as it passes through the carpal tunnel at the wrist.
Epidemiology
- Lifetime prevalence: ~3–6%; annual incidence ~3 per 1,000
- Female:male ratio 3:1
- Peak age: 45–60 years
- Very common in pregnancy (up to 50% in 3rd trimester)
Aetiology
- Idiopathic (most common)
- Pregnancy: fluid retention
- Endocrine: hypothyroidism, diabetes, acromegaly
- Inflammatory: RA (synovitis), gout
- Anatomical: wrist fracture (Colles), ganglion
- Other: obesity, amyloidosis (dialysis-related), repetitive wrist use
Pathophysiology
- Carpal tunnel: rigid canal bounded by carpal bones and flexor retinaculum
- Median nerve + 9 flexor tendons pass through
- Any cause of increased pressure → nerve compression → demyelination → axonal loss (if severe/prolonged)
- Ischaemic and mechanical injury to nerve
Clinical Presentation
Typical Presentation
- Nocturnal paraesthesiae: numbness/tingling in median nerve distribution (thumb, index, middle, radial ring finger)
- Waking at night, shaking hand to relieve symptoms (flick sign)
- Pain may radiate to forearm
- Worse with repetitive wrist use, gripping
Severe/Advanced
- Constant numbness
- Thenar muscle wasting/weakness (abductor pollicis brevis — APB)
- Weakness of thumb opposition and abduction
- Clumsiness, dropping objects
Examination
- Tinel sign: tapping over carpal tunnel reproduces symptoms
- Phalen sign: wrist flexion for 60 seconds reproduces symptoms
- Thenar wasting: APB atrophy (late sign)
- Reduced sensation in median nerve distribution
Red Flags
- Progressive thenar wasting (urgent referral)
- Young patient with bilateral CTS (think systemic cause)
- Neck pain + radiculopathy (cervical cause, double crush)
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Cervical radiculopathy (C6/C7) | Neck pain, dermatomal sensory loss, weakness, reflexes | MRI cervical spine |
| Pronator teres syndrome | Forearm pain, weakness of FPL, no nocturnal symptoms | Nerve conduction studies |
| Peripheral neuropathy | Symmetrical, stocking-glove, all nerve territories | Nerve conduction, HbA1c |
| De Quervain tenosynovitis | Radial wrist pain, Finkelstein positive | Clinical, USS |
| Raynaud phenomenon | Colour change, cold triggers, entire fingers | Clinical |
Diagnosis / Investigation
Special Tests
- Nerve conduction studies (NCS): gold standard — prolonged distal motor latency and sensory latency of median nerve across wrist
- Severity grading: mild (sensory only), moderate (sensory + motor), severe (absent sensory + motor, thenar wasting)
Bloods (if secondary cause suspected)
- TFTs: hypothyroidism
- HbA1c: diabetes
- RF, anti-CCP: RA
- Urate: gout
Imaging
- USS wrist: increased cross-sectional area of median nerve (>10mm²); may identify mass lesion
- X-ray wrist: if post-traumatic (fracture)
Management
Non-pharmacological
- Wrist splint in neutral position: especially at night (first-line; 6-week trial)
- Activity modification: ergonomic assessment, avoid provocative positions
Pharmacological
- Corticosteroid injection: triamcinolone 40mg into carpal tunnel
- ~70% symptom relief at 1 month; ~50% at 1 year
- May be repeated once
- Useful diagnostically (good response predicts surgical success)
Surgical
- Carpal tunnel decompression (open or endoscopic): division of flexor retinaculum
- Indicated: persistent symptoms despite conservative measures, thenar wasting, severe NCS
- ~90–95% success rate
- Most common elective hand surgery in the UK
Pregnancy-related
- Splinting first-line
- Often resolves postpartum
- Surgery delayed until after delivery unless severe
Referral Criteria
- Hand surgery/orthopaedics: persistent symptoms after 6 weeks splinting + injection; thenar wasting
- Neurophysiology: NCS for diagnostic confirmation
- Endocrinology: if secondary cause identified
Prognosis
- Mild CTS: ~30–50% resolve spontaneously (especially pregnancy-related)
- Splinting: ~50–70% improvement
- Corticosteroid injection: ~70% relief at 1 month; many recur
- Surgery: ~90–95% excellent outcomes
- Delay in treatment of severe CTS: risk of irreversible thenar wasting and sensory loss
- Post-surgical: pillar pain (common but temporary); recurrence ~3–5%
- Pregnancy: ~50–70% resolve spontaneously after delivery
Other Relevant Information
Severity Grading (NCS)
| Grade | NCS Findings | Clinical |
|---|---|---|
| Mild | Prolonged sensory latency only | Intermittent paraesthesiae |
| Moderate | Prolonged sensory + motor latency | Constant symptoms |
| Severe | Absent sensory ± motor response | Thenar wasting, weakness |