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Carpal tunnel syndrome (CTS)

Entrapment/compressive neuropathy caused by compression of the median nerve as it travels through the wrist’s carpal tunnel.

Introduction

Entrapment/compressive neuropathy caused by compression of the median nerve as it travels through the wrist’s carpal tunnel.

  • M/C nerve entrapment neuropathy (90% of all neuropathies)
  • M/C form of Repetitive Trauma Disorder (RTD)

History:

Sir James Paget, in 1854, was the first to describe the symptoms of the condition in a patient who had sustained a fracture of the distal radius. In 1913, the French neurologists Pierre Marie and Charles Foix were the first to recommend surgery on the basis of autopsy findings in a patient with bilateral thenar muscle atrophy and what they thought were neuromas in both median nerves just proximal to the transverse carpal ligaments. However, most patients at that time who presented with motor and sensory complaints in the median nerve distribution of their hands were usually diagnosed with compression of the brachial plexus by the first cervical rib. Later, in the 1930s, physicians began to notice what Paget had described 80 years earlier, the frequent association of median nerve compression in patients with fractures of the distal radius. In 1938, the term “carpal tunnel syndrome” (CTS) was coined by Moersch. However, it was not until a series of articles written by George Phalen beginning in 1950 that the condition was popularized.

Anatomy

Carpal tunnel:

Osteofibrous outlet in the volar wrist, lying between flexor retinaculum (FR) and carpal bones
  • Roof: Fibrous transverse carpal ligament (intermediate part of the flexor retinaculum)
  • Contents:
    • 9 tendons: Flexor pollicis longus, 4 flexor digitorum superficialis and 4 flexor digitorum profundus
    • Median nerve (nerve enters the tunnel in the midline or slightly radial to it)
Cross section across wrist | Gray, Henry. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918.

Median nerve:

  • Sensory supply:
    • 3 radial digits
    • Radial half 4th digit
    • Palmar sensory cutaneous branches: Supply cutaneous skin of palm
  • Motor supply:
    • Thenar (recurrent) motor branch
Median nerve palmar distribution | LeBlanc KE, Cestia W. Carpal tunnel syndrome. Am Fam Physician. 2011;83(8):953.

Aetiology

Acute CTS:

Relatively uncommon and is due to a rapid and sustained rise of pressure in the carpal tunnel
  • Radial fracture (M/C)
  • Burns, coagulopathy, local infection and injections

Chronic CTS:

Common and symptoms can persist for months to years.
  • History of repetitive wrist movements (typing, or machine work, etc)
  • Genetic predisposition & female sex
  • Obesity
  • Autoimmune disorders: Rheumatoid arthritis
  • Pregnancy (In the majority of patients symptoms will resolve either spontaneously or will respond to conservative treatment after delivery and it is often bilateral)

Pathophysiology

Neuropathy caused by compression and traction of the median nerve at the level of the carpal tunnel, delimitated by the carpal bones and by the transverse carpal ligament (FR)

Compressive mechanisms:

Detrimental cycle of increased pressure, obstruction of overall venous outflow, increasing local edema, and compromise to the median nerve’s intraneural microcirculation. Nerve dysfunction becomes compromised, and the structural integrity of the nerve itself further propagates the dysfunctional environment– the myelin sheath and axon develop lesions, and the surrounding connective tissues become inflamed and lose normal physiologic protective and supportive function.
A schematic presentation for vascular mechanism of carpal tunnel syndrome and median nerve injury. | HIF-1α – hypoxia-inducible factor 1α, VEGF – vascular endothelial grown factor | Aboonq M. S. (2015). Pathophysiology of carpal tunnel syndrome. Neurosciences (Riyadh, Saudi Arabia), 20(1), 4–9.

Traction mechanism:

Repetitive traction and wrist motion exacerbates the negative environment, further injuring the nerve. In addition, any of the nine flexor tendons traveling through the carpal tunnel can become inflamed and compress the median nerve.

Clinical features

Early symptoms:

In the early presentation of the disease, symptoms most often present at night when lying down and are relieved during the day.
  • Pain, numbness, and paresthesias
    • Typically present in thumb, index finger, middle finger, and the radial half (thumb side) of the ring finger.
    • Pain also can radiate up the affected arm
  • Relieved with ice & rest; provoked by repetitive activity, and night splints.
  • Associated features: Weakness, clumsiness, and temperature changes also are common complaints.
  • Flick sign: Symptoms improve when patient flicks their hand and wrist.
A hand symptom diagram can be a useful tool in diagnosing carpal tunnel syndrome. (A) In the classic pattern, symptoms affect at least two of digits 1, 2, or 3. It includes symptoms in the fourth and fifth digits, wrist pain, and radiation of pain proximal to the wrist, but excludes symptoms on the palm or dorsum of the hand. (B) The probable pattern has the same symptom pattern as the classic pattern, except palmar symptoms are possible unless confined solely to the ulnar aspect. In the possible pattern (not shown), symptoms involve only one of digits 1, 2, or 3. (C) In the unlikely pattern, no symptoms are present in digits 1, 2, or 3. | Katz JN, Stirrat CR, Larson MG, Fossel AH, Eaton HM, Liang MH. A self-administered hand symptom diagram for the diagnosis and epidemiologic study of carpal tunnel syndrome. J Rheumatol. 1990;17(11):1497.

Progressive disease:

With further progression of the disease, symptoms will also be present during the day, especially with certain repetitive activities, such as when drawing, typing, or playing video games. In more advanced disease, symptoms can be constant.
  • Hand weakness
  • Decreased fine motor coordination, clumsiness
  • Thenar atrophy
Picture showing moderate thenar atrophy of the left hand in a woman with bilateral carpal tunnel syndrome | George S. Phalen. The Carpal-Tunnel Syndrome: Seventeen Years’ Experience In Diagnosis And Treatment Of Six Hundred Fifty-Four Hands. J Bone Joint Surg Am 1966; 48:211

Diagnosis

Clinical examination:

  • Palpatory diagnosis: Examination of soft tissue over the median nerve for mechanical restriction
  • Carpal compression test “Durkan’s test”: Applying firm pressure directly over the carpal tunnel for 30 seconds. Positive test if symptoms are reproduced
  • Square sign test: Evaluation to determine the risk of developing carpal tunnel syndrome. Positive test if ratio of wrist thickness/wrist width > 0.7
  • Phalen’s test or ‘reverse prayer’: Flexion of wrists by placing dorsal surfaces of both hands for 1 minute. Positive test if symptoms are reproduced
  • Reverse Phalen’s ‘prayer test’: Extention of both of wrists by placing palmar surfaces of both hands together for 1 minute (as if praying). Positive test is with the reproduction of symptoms.
  • Hoffmann-Tinel sign: Healthcare professional taps immediately over the carpal tunnel to stimulate the median nerve. Positive test if symptoms are reproduced.

USG:

  • Measure cross-sectional area (CSA) of the median nerve
  • Bowing of the flexor retinaculum (FR)
  • Flattening of the flexor retinaculum

Nerve conduction studies (NCS):

Median nerve conduction studies are the GOLD STANDARD diagnostic test
  • Entrapment neuropathies: Delay in conduction velocity at point of compression due to demyelination of the nerve.

Differential diagnosis:

  • Cervical radiculopathy
  • Neuropathies
  • Tendonitis
  • Tenosynovitis

Management

Physical therapy:

If carpal tunnel syndrome is identified early, conservative treatment is recommended.
  • Modifying symptoms provoking wrist movement and decrease repetitive activities if possible
  • Proper hand ergonomics such as placing the keyboard at a proper height
  • Minimizing flexion, extension, abduction, and adduction of the hand when typing.
  • Weight loss and increased aerobic activity
  • Properly fitted nighttime wrist splint

Medical management:

  • Oral steroids
  • Non-steroid anti-inflammatory drugs (NSAIDs)
  • Oral vitamin B6
  • Local corticosteroids injection ± insulin
A ventral wrist display showing the anatomic association of the flexor carpi radialis and the flexor carpi ulnaris tendons to the palmaris longus tendon and the median nerve. When treating carpal tunnel syndrome with corticosteroid injection, the traditional method has been to (A) inject medial to the palmaris longus tendon. An alternative is to (B) inject lateral to the palmaris longus tendon. | LeBlanc KE, Cestia W. Carpal tunnel syndrome. Am Fam Physician. 2011;83(8):957.

Carpal tunnel release/decompression surgery

Definitive treatment for persistent carpal tunnel syndrome if NCS shows significant axonal degeneration
  • Minor surgery: Transverse carpal ligament or flexor retinaculum is cut, opening more space in the carpal tunnel and decreasing pressure on the median nerve

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