Carpal Tunnel Syndrome

Overview

Carpal tunnel syndrome occurs when there is pressure and squeezing (entrapment) of an important nerve in the hand called the median nerve. This pressure causes median nerve injury and results in pain, numbness, and weakness in the hand and wrist.

The median nerve and finger flexor tendons pass through a narrow space in the wrist called the carpal tunnel, formed by the carpal bones and enclosed by a fibrous band (transverse carpal ligament or flexor retinaculum). Because the carpal tunnel is very narrow, any irritation of the tendons or any swelling in this space may entrap and compress the median nerve.

Carpal tunnel syndrome tends to occur in adults age 30 to 60 years old and is three times more likely in women than men. This is a very common condition associated with a variety of work-related or medical factors.

With proper treatment, most people completely recover and only a few have permanent nerve damage and loss of hand function.

Causes and Risk Factors

Flexor retinaculum (transverse carpal ligament) and the flexor tendons beneath itThe cause of carpal tunnel syndrome is not completely understood, but the disorder is associated with factors that compress the median nerve and affect the sensory and motor functions of the hand.

Associated Factors:  

  • Gender and genetic predisposition (women or people with small carpal tunnels)
  • Work-related activities that involve repetitive hand motions, especially grasping
  • Use of vibrating handheld tools
  • Sports involving repetitive hand motions
  • Injury to the wrist
  • Rheumatoid arthritis
  • Pregnancy
  • Thyroid disease
  • Diabetes

Workers with jobs requiring repetitive use of their hands are more susceptible to carpal tunnel syndrome. Examples include meatpackers, assembly line workers, grocery checkers, garment workers, dental hygienists, and musicians. So far, studies have not proven that excessive use of a computer keyboard or mouse causes carpal tunnel syndrome. In fact, assembly workers are at much higher risk than typists.

Symptoms

Early symptoms include pain and paresthesias (tingling, numbness, and burning sensations) of the thumb, index finger, and middle finger especially at night and after certain activities like driving or holding a book. If the problem worsens, patients experience hand weakness, dropping things, difficulty gripping objects, and clumsiness. Symptoms usually start in the dominant hand, but may be experienced in both hands.

Diagnosis and Treatment

Median nerve in the wrist and handIt is important to diagnose and treat carpal tunnel syndrome as early as possible to prevent permanent median nerve damage, loss of hand function, and disability. Usually the diagnosis is based on symptoms and physical exam findings indicative of median nerve entrapment, but sometimes nerve testing is necessary.

Physical examination:

  • Decreased feeling in the thumb, index finger, and middle finger.
  • Paresthesias reproduced by tapping the wrist over the median nerve (positive Tinel sign) or flexing the wrist for one minute (Phalen maneuver).
  • Weakness and wasting of the muscles at the base of the thumb (thenar atrophy) are late findings of chronic nerve injury.

Nerve testing:

  • Nerve conduction velocity testing determines how well electrical signals flow through the median nerve.
  • Electromyography evaluates the function of nerves and muscles.

Initial Treatment:

  • Avoidance of activities that trigger symptoms.
  • Hand rest for a minimum of two weeks.
  • Immobilization with wrist splints.
  • Ice packs to reduce swelling.

Medications:

  • Nonsteroidal anti-inflammatory drugs like ibuprofen.
  • Corticosteroid injection (a steroid reduces swelling and inflammation).
  • Prednisone (an oral steroid).

Exercise:

  • Physical therapy to restore hand strength.
  • Occupational therapy to maintain or improve daily living activities and work skills.

Alternative Treatments:

  • Yoga has been shown to improve strength and relieve pain in carpal tunnel syndrome.
  • Acupuncture may improve symptoms in some patients, but more research is needed to evaluate its effectiveness.

Surgery

Carpel tunnel release surgery is recommended for patients with 6 months of persistent symptoms. This operation involves cutting the transverse carpal ligament at the wrist to provide more space in the carpal tunnel and relieve the pressure on the median nerve.

Open carpal tunnel release is the more traditional approach, which involves making a 2-inch incision in the wrist and cutting the transverse carpal ligament. Endoscopic carpal tunnel release uses two tiny incisions, a small camera, and instruments to cut the transverse carpal ligament. This less invasive procedure shortens the patient’s recovery time.

Both types of surgeries are performed under local anesthesia: medication is injected to numb the tissues and prevent the patient from feeling the surgery, so the patient does not need to be deeply asleep. After surgery, patients need physical therapy to regain hand strength and function, and most patients make a full recovery.

Prevention

Employers can redesign equipment and adapt activities to fit the human body based on a field of study known as ergonomics. Work areas may be redesigned to allow people to maintain a neutral wrist position while working. Workers are advised to reduce repetitive motions by taking frequent rest breaks, wearing wrist splints, and rotating tasks with other workers. Although there are no studies to prove that these programs prevent carpal tunnel syndrome, they are commonly recommended to prevent workplace injuries.

Sources

  • Netscher D, Murphy K, Florell N. Ch 70. Hand Surgery. In: Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook Of Surgery. 19th ed. Philadelphia, PA: Elsevier Saunders: 2012.
  • Katirji B, Koontz D. Ch 76. Disorders of Peripheral Nerves. In: Daroff R, Fenichel GM, Jankovic J, Mazziotta J, eds. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders: 2012.
  • Carpal Tunnel Syndrome Information Page. National Institute of Neurological Disorders and Stroke website. http://www.ninds.nih.gov/disorders/Carpal_tunnel/Carpal_tunnel.htm. Accessed April 18, 2014.