Fact-sheet: Carpal tunnel syndrome


Updated on 03/22/2021 at 10:43 AM

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Definition

The most common entrapment syndrome.
Prevalence: 1%.

Female predominance

Secondary to compression of the median nerve

Congestive edema of the nerve, then demyelinating fibrosis in long-standing forms

Very often an occupational disease

Most often idiopathic.
Secondary causes:
- flexor tenosynovitis of the fingers (rheumatoid arthritis...)
- post-fracture malunion
- synovial cyst
- intracanalicular tumor: lipoma, hemangioma
- tumor of the median nerve (schwannoma, fibrolipoma)
- diabetic neuropathy
- amyloidosis, mucopolysaccharidosis
- Hypothyroidism, Hyperparathyroidism
- Acromegaly
- chronic hemodialysis
- pregnancy, breastfeeding

Clinical features

Wrist paresthesias, often painful with nocturnal exacerbation

Radiation toward the forearm

Paresthesias of the palmar surface of the first three fingers and the radial half of the 4th finger + dorsal surface of the middle and distal phalanges of these same fingers

Tinel's sign: reproduction of symptoms upon percussion of the palmar surface of the wrist

Phalen's maneuver: reproduction of symptoms during forced hyperflexion of the hand on the forearm

Advanced forms: thenar amyotrophy

Radiography

Search for indirect signs: osteoarthritis, malunion or malunited fracture of the distal radius, lunate dislocation

Ultrasound

Alternative to electromyography

Useful in atypical presentations (sudden onset, young patient, suspected secondary form, discordance between clinical findings and ENMG)

Median nerve:
- oval shape,
- located immediately deep to the flexor retinaculum,
- medial to the flexor pollicis longus tendon
- anterior to the superficial flexor tendons of the second and third fingers.

Early-stage form:
Often normal morphology

Established form:

  • Notch sign: abrupt change in nerve caliber; enlarged proximal to the stenosis, flattened within the canal.
  • Nerve edema: thickening of the nerve proximal to the stenosis. Homogeneous hypoechoic appearance with loss of the fascicular pattern
  • Intraneural Doppler hyperemia, to be sought in the enlarged portion of the nerve.
  • Decreased nerve mobility during flexion/extension movements (compared with the contralateral nerve
  • Increased nerve cross-sectional area > 12 mm2 (measured proximal to or at the proximal portion of the carpal tunnel
  • Bowing of the flexor retinaculum > 4 mm
  • Nerve flattening ratio > 3 (transverse diameter of the nerve / anteroposterior diameter)

MRI

Second-line, after ultrasound.

  • Median nerve: Hypertrophy with the ratio of the nerve cross-sectional area at the pisiform level / cross-sectional area at the radiocarpal joint level > 2
  • Edema: intraneural T2 hyperintensity
  • Possible enhancement after contrast administration
  • Palmar bowing of the flexor retinaculum
  • Edema of the thenar eminence muscles (abductor pollicis brevis, opponens pollicis, and superficial head of the flexor pollicis brevis); or even atrophy at a late stage

Management

Medical treatment: indicated in cases of pure sensory involvement

  • Nighttime resting splint, NSAIDs
  • Ultrasound-guided injection of corticosteroid suspension into the carpal tunnel

Surgical treatment: indicated in cases of deficit signs (clinical or ENMG), failure of medical treatment, or secondary forms

  • Surgical release of the flexor retinaculum
  • Ultrasound-guided percutaneous release