Carpal tunnel syndrome (CTS) is a peripheral neuropathy caused by chronic or acute compression of the median nerve under the transverse carpal ligament. CTS is the most common form of entrapment neuropathy, a group that includes cubital tunnel syndrome, radiculopathies, and tarsal tunnel syndrome. It is characterized by both sensory disturbances (pain, tingling, and numbness) and motor symptoms (weakened thenar muscles leading to weakened pinch and grip of the thumb) in the area innervated by the median nerve distal to the carpal tunnel. Several occupational and nonoccupational risk factors (e.g., manual labor, age, sex, diabetes) have been associated with CTS. Diagnosis is usually clinical, supported by symptoms and results of provocative tests for CTS (e.g., hand elevation test, carpal compression test, and Phalen test). Additional testing (e.g., electrodiagnostic studies) is indicated if there is diagnostic uncertainty. Patients with mild to moderate symptoms are generally managed conservatively (e.g., immobilization with a splint, local steroid injections). Surgical release of the transverse carpal ligament with decompression of the median nerve may be indicated for patients with severe disease (e.g., atrophy of the thenar eminence) or symptoms refractory to conservative treatment.
Risk factors 
- Previous fracture of the wrist
- Traumatic dislocation of the lunate 
- Manual work: increased risk in workers using vibrating tools or prolonged, forceful, and repetitive flexion/extension of the wrist 
- Rheumatoid arthritis and other types of chronic inflammation of the tendon sheaths 
- Pregnancy and puerperium 
- Renal failure and dialysis-associated deposition of amyloid 
- Diabetes mellitus
- Hypothyroidism 
- The carpal tunnel is a narrow fibro-osseous structure at the level of the palmar aspect of the wrist, delimited by the carpal bones and the transverse carpal ligament, which contains flexor tendons and the median nerve.
- Pressure increase within the carpal tunnel → compression of contained structures → impaired blood flow and altered microvascular structure of the median nerve → inflammatory reaction → edema and hypoxia → axonal degeneration 
- Develop in the areas innervated by the median nerve: palmar surface of the thumb, index, and middle fingers, and radial half of the ring finger.
- Typically worsen at night
- Patients often report that symptoms improve by shaking the hand (flick sign). 
Severely affected patients may report:
- Dropping objects; and difficulty with fine motor skills (e.g., buttoning up clothing) secondary to weakened finger pinch and grip strength
- Disappearance of pain 
Motor deficits are typically only seen in severe disease. 
Examination findings 
- Mild disease: Initial examination is often normal; symptoms only develop with provocative tests for CTS.
- Severe disease: Findings of both sensory and motor deficits may be seen. 
Examination of the sensory system
- May show decreased sensation in the area innervated by the median nerve distal to the carpal tunnel 
- Usually, there is no loss of sensation of the palmar surface of the thenar eminence because it is innervated by the superficial branch of the median nerve, which arises 5–7 cm proximal to the carpal tunnel and is, therefore, not compressed. 
- Examination of the motor system: may show weakness in thumb abduction and opposition as well as thenar atrophy 
Sensory innervation of the thenar eminence is not affected in CTS.
Examine the entire upper limb to rule out differential diagnoses of CTS. 
General principles 
- Usually a clinical diagnosis, based on classic combined with positive 
- Consider additional testing (e.g., electrodiagnostic studies, imaging) in:
- Diagnostic uncertainty
- Severe cases (e.g., those that may require surgical intervention)
Provocative tests for CTS 
Commonly used provocation tests
- Phalen test: The patient's wrist is held in full flexion (90°) for one minute. 
- Tinel sign: The examiner percusses or taps with the fingertips over the carpal tunnel.
- Hand elevation test: The patient holds both hands above their head for one minute.
- Carpal compression test: The examiner uses a finger to apply moderate pressure directly over the carpal tunnel for 30 seconds.
Do not use a single provocative test to diagnose CTS; using a combination of tests increases diagnostic accuracy. 
Electrophysiological tests 
- Indications 
Nerve conduction studies (confirmatory test): show impaired median nerve conduction along the carpal tunnel 
- Prolonged sensory and 
- May be normal in patients with mild disease
- Usually ordered to rule out alternative diagnoses
- May show abnormal spontaneous activity (e.g., fibrillation potentials) or altered action potential morphology 
- Nerve conduction studies (confirmatory test): show impaired median nerve conduction along the carpal tunnel 
Additional evaluation 
- Imaging: Consider if structural abnormalities or alternative diagnoses are suspected. 
- Laboratory studies: Consider based on clinical features, e.g., or thyroid function tests. 
- Mild to moderate disease 
- Severe or refractory disease: Refer to a hand specialist for possible surgery. 
Conservative management 
- Treatment of underlying comorbidities: see “Etiology of CTS.”
- Immobilization: splinting of the wrist in a neutral position. 
- First-line: steroid injection, e.g., methylprednisolone 
- Alternative: oral glucocorticoids, e.g., prednisone 
- Should only be used short-term (e.g., 2–4 weeks); monitor for . 
- Can provide up to 8 weeks of symptomatic relief 
- Physical therapy and exercise: e.g., nerve glide exercises, therapeutic ultrasound, and carpal bone mobilization 
- Indications: severe disease or refractory symptoms
Patients with severe disease may not fully recover function but nerve conduction studies should show an improvement. 
Recurrence of CTS is rare (0.5–3%). 
We list the most important complications. The selection is not exhaustive.
Special patient groups
Carpal tunnel syndrome in pregnancy 
- Epidemiology 
- Etiology 
- Clinical features 
- Modifications to diagnostics of CTS: none
- Modifications to treatment of CTS