Description

• Symptomatic compression neuropathy of the median nerve
• Increased pressure within the carpal tunnel leads to compression of the median nerve and characteristic motor-sensory findings.
• The dorsal aspect of the carpal tunnel is composed of the carpal bones. The transverse carpal ligament defines the palmar boundary.
  • The carpal tunnel contains nine flexor tendons and the median nerve.
• Symptoms most commonly affect the dominant hand; >50% of patients will experience bilateral symptoms.
• Most expensive upper extremity musculoskeletal disorder; >$2 billion per year
• Carpal tunnel release (CTR) is one of the most frequently performed hand/wrist procedures, with approximately 600,000 CTR procedures per year.
• Median time lost by U.S. workers with carpal tunnel syndrome (CTS) = 28 days
• System(s) affected: musculoskeletal, nervous

Epidemiology

Predominant age: 40 to 60 years; predominant sex: female > male (3:1 to 10:1)

Incidence

• Two peaks: late 50s (women), late 70s (both genders)
• Incidence up to 276/100,000 has been reported.
• Incidence increases with age.

Prevalence

• About 3% of the population (4% in women and 2% in men); 50 cases per 1,000 individuals per year in the United States
• 14% in diabetics without neuropathy and 30% in patients with diabetic neuropathy

Etiology and Pathophysiology

• Combination of mechanical trauma, inflammation, increased pressure, and ischemic injury to the median nerve within the carpal tunnel
• Acute CTS caused by rapid and sustained pressure in carpal tunnel, usually secondary to trauma, may require urgent surgical decompression.
• Distal radius fractures and volar lunate dislocations increase risk.
• Chronic CTS divided into four categories:
  • Idiopathic: combination of edema and fibrous hypertrophy without inflammation
  • Anatomic: persistent median artery, ganglion cyst, infection, space-occupying lesion in carpal tunnel
  • Systemic: associated with conditions such as obesity, diabetes, hypothyroidism, rheumatoid arthritis, amyloidosis, scleroderma, renal failure, and drug toxicity
  • Exertional: repetitive use of hands and wrists, repeated palmar impact, use of vibratory tools

Genetics

• Unknown; however, a familial type has been reported.
• More likely to experience CTS if there is a first-degree relative with CTS

Risk Factors

• Prolonged postures in extremes of wrist flexion and extension including activities such as gardening, cycling, or tennis; repetitive exposure to vibration (motorcycle riding)
  • There is an insufficient evidence to implicate computer use in the development of CTS.
  • Jobs most at risk for CTS: use of vibratory tools, food processing and packing, dairy and poultry workers, and assembly workers
• Alterations of fluid balance: pregnancy, rheumatoid arthritis, obesity, renal failure, hypothyroidism, congestive heart failure, hemodialysis
  • CTS is the most common neuropathy in patients with rheumatoid arthritis.
• Neuropathic factors: diabetes, alcoholism, vitamin deficiency, or exposure to toxins
• More common in patients with concomitant migraine headaches

General Prevention

There is no known prevention for CTS. It is recommended to take occasional (e.g., hourly) breaks when doing repetitive work involving hands or if prolonged occupational exposure to vibratory tools.

Commonly Associated Conditions

• Diabetes, obesity; pregnancy; hypothyroidism
• Osteoarthritis of small joints of hand and wrist
• Hyperparathyroidism, hypocalcemia
• Hemodialysis