Most common compressive neuropathy; due to compression of median nerve at carpal tunnel. Symptoms: nocturnal paresthesias, hand clumsiness, thenar atrophy. Tests: Phalen’s, Tinel’s, Durkan’s compression test. Investigations: Nerve conduction study (slowed conduction across wrist). Treatment: splints, NSAIDs, steroid injection, surgical release for refractory cases.
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Overview & Anatomy
Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment neuropathy, affecting approximately 3–6% of the adult population. It results from compression of the median nerve within the carpal tunnel — a rigid fibro-osseous canal bounded by the carpal bones posteriorly and the transverse carpal ligament (flexor retinaculum) anteriorly. The condition is characterised by pain, paraesthesia, and eventually weakness and thenar wasting in the distribution of the median nerve.
Carpal tunnel contents: the median nerve and nine flexor tendons — four FDS tendons, four FDP tendons, and FPL; the ulnar nerve and vessels pass through Guyon`s canal, which is superficial and medial to the carpal tunnel
Incidence: 3–6% of general population; female:male ratio 3–5:1; bilateral in approximately 50%; peak incidence 45–60 years
Pathophysiology: elevated pressure within the carpal tunnel (normal <10 mmHg) → ischaemia of the median nerve → demyelination → axonal degeneration in severe cases; wrist flexion and extension both increase carpal tunnel pressure significantly; normal pressure increases from approximately 10 mmHg to 90 mmHg in full flexion and 30 mmHg in full extension
Most common — no identifiable cause; related to tenosynovial thickening without inflammatory cause
Pregnancy-associated CTS: most common cause of CTS in women under 40; third trimester most commonly affected; usually bilateral; resolves in most cases after delivery; treat non-operatively during pregnancy (wrist splints); surgery rarely needed and deferred until post-partum
Clinical Presentation & Diagnosis
Classic symptoms: pain, tingling, and numbness in the median nerve distribution (thumb, index, middle, and radial half of ring finger); symptoms worse at night (nocturnal paraesthesia) and with sustained wrist flexion; patients "shake out" the hand for relief (flick sign); weakness and dropping objects in advanced disease
The little finger is spared — if little finger symptoms are present, consider ulnar nerve entrapment (Guyon`s canal) or combined pathology
Thenar wasting: late sign — atrophy of abductor pollicis brevis (APB), opponens pollicis (OP), and flexor pollicis brevis (FPB — superficial head) from chronic motor axon loss; once wasting is present, irreversible axonal damage has occurred; expedited decompression is required
Clinical Test
Technique
Sensitivity / Specificity
Phalen test
Wrists in maximal flexion for 60 seconds; positive if paraesthesia reproduced in median distribution
Sensitivity 68–75%; specificity 67–73%
Tinel sign
Percussion over carpal tunnel at the wrist crease; positive if tingling radiates into median nerve distribution
Sensitivity 48–60%; specificity 73–80%
Hand elevation test / Flick sign
Patient shakes hand to relieve nocturnal symptoms; elevation of hands relieves paraesthesia; symptom-based
Flick sign sensitivity ~93%; most sensitive for CTS
Carpal compression test (Durkan)
Direct pressure over carpal tunnel for 30 seconds; positive if paraesthesia reproduced
Sensitivity 64–87%; specificity 83–90%; better than Phalen
APB weakness / atrophy
Assess abductor pollicis brevis strength; wasting in severe disease
Late finding; irreversible motor damage if present
Investigations
Nerve conduction studies (NCS) / EMG: gold standard investigation — confirms CTS and grades severity; prolonged distal sensory latency is the most sensitive early finding; prolonged distal motor latency (DML) in moderate disease; reduced SNAP amplitude in severe; EMG shows denervation of thenar muscles in severe CTS; NCS should be performed before surgery in most cases (exceptions: classic symptoms + positive examination with clinical diagnosis, urgent case with wasting)
NCS severity grading: mild (sensory only abnormal); moderate (sensory + motor latency prolonged); severe (sensory + motor + EMG denervation changes)
MRI and USS: for atypical presentations; identify space-occupying lesions; USS assesses median nerve cross-sectional area (CSA >10 mm² = enlarged) and can guide injection
Blood tests: TFTs (hypothyroidism), HbA1c (diabetes), RA serology — screen for systemic causes especially in bilateral CTS or young patients
Non-Operative Management
Wrist splinting: neutral position splint worn at night; reduces nocturnal carpal tunnel pressure; most effective for mild-moderate CTS; approximately 30–50% short-term improvement; does not alter natural history
Corticosteroid injection: USS-guided injection into the carpal tunnel (adjacent to the median nerve, ulnar to the palmaris longus tendon); provides significant short-term relief in approximately 80% of patients; duration of benefit 1–3 months; useful for diagnosis confirmation, pregnancy-related CTS, and bridging to surgery; predictors of good long-term response: mild disease, short symptom duration, positive response to injection
Injection technique: the nerve is ulnar to the axis of the palmaris longus tendon (if present); injection should be slightly ulnar to PL at the wrist crease; never inject into the nerve — intraneural injection causes chemical neuritis
Non-operative treatment is appropriate for mild-moderate CTS without wasting; surgical decompression indicated for: moderate-severe NCS changes, thenar wasting, failure of conservative treatment, pregnancy-related severe CTS
Surgical Management — Carpal Tunnel Release
Open carpal tunnel release (OCTR): longitudinal incision ulnar to thenar crease; complete division of the flexor retinaculum from proximal to distal; visualisation of the entire carpal tunnel; identification of anomalous anatomy (accessory muscles, anomalous palmar vessels); thenar branch of median nerve at risk — the recurrent motor branch (Riche-Cannieu anastomosis) usually exits distal to the tunnel but anomalous transligamentous or subligamentous courses occur in 20–25%; must be identified and protected at surgery
Endoscopic carpal tunnel release (ECTR): one-portal (Agee) or two-portal (Chow) technique; smaller incisions; faster return to work; lower incidence of pillar pain; equivalent long-term results to OCTR; higher rate of incomplete release and transient nerve injury than OCTR in early learning curve; safe and effective in experienced hands
Outcomes: approximately 85–90% of patients achieve good or excellent results; sensory improvement precedes motor recovery; complete recovery of severe wasting may not occur; patient counselling essential regarding realistic expectations
Pillar pain: pain at the thenar and hypothenar eminences after carpal tunnel release; from division of the transverse carpal ligament and its attachments to the surrounding musculature; affects approximately 20–30% post-operatively; usually resolves within 3–6 months; not a complication of incorrect surgery — an expected sequela; managed with desensitisation physiotherapy
Complications: wound pain and scar, pillar pain, incomplete release (most common cause of failure — distal extent not divided), recurrence, nerve injury (recurrent motor branch, palmar cutaneous branch, digital nerves), bowstringing of flexor tendons (rare — excision of too much retinaculum)
Consultant-Level Considerations
Recurrent CTS after carpal tunnel release: most common cause is incomplete division of the flexor retinaculum — the distal edge is most often missed; scar tethering around the median nerve is the second most common cause; USS or MRI assess nerve morphology and scar; revision surgery is more complex — extensive adhesiolysis, possible nerve wrap with fat or HA membrane, and synovectomy; NCS confirms ongoing median neuropathy; outcomes of revision are inferior to primary release
Palmar cutaneous branch of the median nerve: arises approximately 5 cm proximal to the wrist crease and runs on the radial side of the FCU tendon, piercing the deep fascia to supply the thenar eminence skin; at risk during CTR incision if incision is too radial; injury causes a painful neuroma and numbness in the thenar skin; incision should be in line with the ring finger ray, just ulnar to the thenar crease, to avoid this nerve
Acute carpal tunnel syndrome: sudden onset in a young patient, often after trauma (distal radius fracture, perilunate dislocation), infection, or coagulation disorder; signs of acute compartment syndrome of the hand; manage with emergency decompression; associated with perilunate dislocation requires simultaneous carpal reduction/fixation + CTR
CTR in the context of distal radius fracture: acute CTS post-fracture requires urgent CTR within hours; delayed CTS (days to weeks) may respond to elevation and closed reduction; CTR should accompany fracture fixation if CTS is present or develops perioperatively; do not delay neural decompression
Exam Pearls
Carpal tunnel contents: median nerve + 9 tendons (4 FDS, 4 FDP, 1 FPL); ulnar nerve in Guyon`s canal (superficial and medial)
Classic: nocturnal paraesthesia in median distribution; flick sign (shake hand for relief); thumb/index/middle/radial ring affected; little finger SPARED
Thenar wasting = late sign = urgent decompression; irreversible axonal loss may mean incomplete motor recovery even after CTR
Flick sign: most sensitive clinical test (93%); Carpal compression test (Durkan): most sensitive/specific formal test
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References
Phalen GS. The carpal tunnel syndrome. J Bone Joint Surg Am. 1966;48(2):211–228.
Tinel J. Le signe du fourmillement dans les lesions des nerfs peripheriques. Presse Med. 1915;23:388–389.
Durkan JA. A new diagnostic test for carpal tunnel syndrome. J Bone Joint Surg Am. 1991;73(4):535–538.
American Academy of Orthopaedic Surgeons. Clinical practice guideline on the diagnosis of carpal tunnel syndrome. AAOS, 2016.
Agee JM et al. Endoscopic release of the carpal tunnel. J Hand Surg Am. 1992;17(5):814–821.
Chow JC. Endoscopic release of the carpal ligament. J Hand Surg Am. 1989;14(6):1064–1067.
Keith MW et al. Evidence-based clinical practice guidelines on the diagnosis of carpal tunnel syndrome. J Hand Surg Am. 2009.
Greens Operative Hand Surgery. 7th Edition. Elsevier.
Campbells Operative Orthopaedics. 14th Edition. Elsevier.
Orthobullets — Carpal Tunnel Syndrome.
