Carpal tunnel syndrome

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.

• Most common entrapment neuropathy (90% of all cases) ^[1]
• The prevalence and yearly incidence of CTS may change according to several occupational and nonoccupational factors.

Epidemiological data refers to the US, unless otherwise specified.

CTS is caused by compression of the median nerve in the carpal tunnel, under the transverse carpal ligament. ^[2]

Risk factors ^[2][3][4]

• Previous fracture of the wrist
• Traumatic dislocation of the lunate ^[5]
• Manual work: increased risk in workers using vibrating tools or prolonged, forceful, and repetitive flexion/extension of the wrist ^[6]
• Rheumatoid arthritis and other types of chronic inflammation of the tendon sheaths ^[3]
• Pregnancy and puerperium ^[7]
• Obesity
• Osteoarthritis
• Systemic amyloidosis
• Renal failure and dialysis-associated deposition of amyloid ^[4][8]
• Diabetes mellitus
• Hypothyroidism ^[9]
• Acromegaly

• 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 ^[10][11]

Symptoms ^[12]

• 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.
  • Paresthesia: burning sensation, tingling
  • Loss of sensation/numbness
  • Pain: may radiate to the forearm and/or upper arm
• Typically worsen at night
• Patients often report that symptoms improve by shaking the hand (flick sign). ^[12]
• 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 ^[12]

Motor deficits are typically only seen in severe disease. ^[12]

Examination findings ^[12]

• 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. ^[12]
• Examination of the sensory system
  • May show decreased sensation in the area innervated by the median nerve distal to the carpal tunnel ^[2][12]
  • 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. ^[12]
• Examination of the motor system: may show weakness in thumb abduction and opposition as well as thenar atrophy ^[2][12]

Sensory innervation of the thenar eminence is not affected in CTS.

The "pope's blessing" (inability to flex the first three digits when making a fist) is not a symptom of CTS. It is only seen in proximal lesions of the median nerve

Examine the entire upper limb to rule out differential diagnoses of CTS. ^[12]

General principles ^[2][12]

• Usually a clinical diagnosis, based on classic clinical features of CTS combined with positive provocative tests for CTS ^[2]
• 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 ^[2][12]

• Overview
  • Considered positive when sensory symptoms (e.g., pain, paresthesias) are elicited along the distribution of the median nerve distal to the carpal tunnel ^[12]
  • Usually performed in combination as use of a single provocative test has low sensitivity and specificity ^[2][12]
• Commonly used provocation tests
  • Phalen test: The patient's wrist is held in full flexion (90°) for one minute. ^[13]
  • 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. ^[2]

Electrophysiological tests ^[2][12]

• Indications ^[2][12]
  • Diagnostic uncertainty or atypical presentation ^[2]
  • To rule out alternative diagnoses (e.g., polyneuropathy, radiculopathy)
  • Presurgical evaluation ^[12]
• Modalities
  • Nerve conduction studies (confirmatory test): show impaired median nerve conduction along the carpal tunnel ^[12]
    • Prolonged sensory and distal motor latency ^[14]
    • May be normal in patients with mild disease
  • Electromyogram ^[15]
    • Usually ordered to rule out alternative diagnoses
    • May show abnormal spontaneous activity (e.g., fibrillation potentials) or altered action potential morphology ^[14]

Electrodiagnostic studies are not necessary to confirm a clinical diagnosis of CTS but should be ordered when the diagnosis is uncertain and for patients scheduled to have surgery. ^[2][12]

Additional evaluation ^[2][12][16]

• Imaging: Consider if structural abnormalities or alternative diagnoses are suspected. ^[12][16]
  • First line: x-ray wrist to rule out bony pathology ^[16]
  • If x-ray is normal, consider ultrasound or MRI without IV contrast. ^[16]
    • Findings include increased cross-sectional area of the median nerve and nerve flattening. ^[16]
    • Can also help to evaluate for tenosynovitis and mass lesions ^[12][16]
• Laboratory studies: Consider based on clinical features, e.g., screening for diabetes or thyroid function tests. ^[12]

• Carpometacarpal arthritis of the thumb
• Arthritis of the wrist
• Cervical radiculopathy (C6)
• De Quervain tendinopathy
• Peripheral neuropathy
• Pronator syndrome
• Raynaud phenomenon
• Ulnar neuropathy
• Vibration white finger

The differential diagnoses listed here are not exhaustive.

Approach ^[2][12]

• Mild to moderate disease ^[12]
  • Trial immobilization or glucocorticoid injection.
  • No response after 6 weeks ^[12]
    • Assess for adherence.
    • Trial alternate conservative methods.
• Severe or refractory disease: Refer to a hand specialist for possible surgery. ^[12]

Conservative management ^[2][12]

• Treatment of underlying comorbidities: see “Etiology of CTS.”
• Immobilization: splinting of the wrist in a neutral position. ^[2][12][17]
• Glucocorticoids
  • First-line: steroid injection, e.g., methylprednisolone ^[12]
    • Consider ultrasound guidance to reduce the risk of nerve or tendon injury.
    • A single injection can provide symptomatic relief lasting from 10 weeks to 1 year. ^[12]
  • Alternative: oral glucocorticoids, e.g., prednisone ^[12]
    • Should only be used short-term (e.g., 2–4 weeks); monitor for side effects of glucocorticoid therapy. ^[2][12]
    • Can provide up to 8 weeks of symptomatic relief ^[12]
• Physical therapy and exercise: e.g., nerve glide exercises, therapeutic ultrasound, and carpal bone mobilization ^[12]

Oral analgesia (e.g., NSAIDs, gabapentin) is not effective in managing CTS. ^[2][12]

Surgery ^[2][12]

• Indications: severe disease or refractory symptoms
• Method
  • Open or endoscopic release of the transverse carpal ligament ^[12][15]
  • The transverse carpal ligament is divided to increase space for the median nerve in the carpal tunnel. ^[15]
• Follow-up
  • Immobilization is not recommended after surgery. ^[2]
  • Most patients return to normal activities within 2 weeks. ^[12]

Patients with severe disease may not fully recover function but nerve conduction studies should show an improvement. ^[12]

Recurrence of CTS is rare (0.5–3%). ^[18]

We list the most important complications. The selection is not exhaustive.

Carpal tunnel syndrome in pregnancy ^[7]

• Epidemiology ^[7][19]
  • Most commonly seen entrapment neuropathy during pregnancy ^[7]
  • Occurs in up to 62% of pregnant women ^[7]
• Etiology ^[19]
  • Hormone-mediated changes ^[20]
    • Weight gain and fluid retention ^[19]
    • Changes to the musculoskeletal system ^[19]
    • Edema of the wrist
  • Gestational diabetes
  • Gestational hypertension
• Clinical features ^[7]
  • Similar to the general population (see “Clinical features of CTS”)
  • Patients commonly present in the third trimester (but can present at any stage).
  • Often bilateral
• Modifications to diagnostics of CTS: none
• Modifications to treatment of CTS
  • Conservative management is recommended during pregnancy as symptoms often resolve after delivery. ^[7][21]
  • Surgery may be required if symptoms persist postpartum. ^[7][22]