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Distal median nerve dysfunction is a form of peripheral neuropathy that affects the movement of or sensation in the hands. Peripheral means further out from the spinal cord.

A common type of distal median nerve dysfunction is carpal tunnel syndrome.

Dysfunction of one nerve group, such as the distal median nerve, is called a mononeuropathy. Mononeuropathy means there is a local cause of the nerve damage, although occasionally body-wide ( systemic) disorders may cause isolated nerve damage. An example is mononeuritis multiplex, where several nerve bundles are affected.

Distal median nerve dysfunction occurs when the nerve is inflamed, trapped, or injured by trauma. Perhaps the most common reason is trapping (entrapment), which puts pressure on the nerve where it passes through a narrow area. Wrist fractures may injure the median nerve directly or may increase the risk for trapping a nerve later on.

Inflammation of the tendons ( tendonitis) or joints ( arthritis) can also cause nerve compression.

Conditions that affect connective tissue or cause deposits to form in tissue can block blood flow and lead to nerve compression. Such conditions include:

• Acromegaly
• Hypothyroidism
• Multiple myeloma
• Pregnancy

In some cases, no cause can be identified.

• Pain in the wrist or hand that wakes you up at night
  • May be severe
  • Pain may be felt in other areas (this is called referred pain)
• Sensation changes in the thumb and first two fingers, such as:
  • Burning feeling
  • Decreased sensation
  • Numbness
  • Tingling
• Weakness of the hand that causes you to:
  • Drop things
  • Have difficulty grasping objects

Examination may show decreased sensation in the thumb side of the hand. This is called the "radial" side. There may be weakness of the thumb and difficulty using it to pinch.

Tests that reveal distal median nerve dysfunction may include:

• Electromyogram (EMG)
• Nerve conduction tests
• Nerve biopsy (rarely needed)

Tests are guided by the suspected cause of the dysfunction as suggested by the patient's history, symptoms, and pattern of symptom development. They may include various blood tests, x-rays, imaging scans, or other tests and procedures.

Treatment is aimed at correcting the underlying cause.

If the median nerve is affected by carpal tunnel syndrome, a wrist splint can reduce further injury to the nerve and help relieve symptoms. It is often enough to wear the splint only at night, to give the area a rest and allow inflammation to decrease.

In some cases, no treatment is required and recovery is happens on its own. Over-the-counter or prescription medication may be needed to control nerve pain (neuralgia).

If other nerves are also affected, it is necessary to look for an underlying medical problem that can affect nerves. Medical conditions such as diabetes and kidney disease can damage nerves. In these cases, treatment is directed at the underlying medical condition.

Physical therapy exercises may be appropriate for some people to maintain muscle strength. Orthopedic assistance may maximize the ability to use the hand. Such therapy may involve braces, splints, or other appliances. Vocational counseling, occupational therapy, occupational changes, job retraining, or other measures may be recommended.

Some patients with carpal tunnel syndrome may need surgery. See: Carpal tunnel release

If the cause of the nerve dysfunction can be identified and successfully treated, there is a possibility of full recovery. In some cases, there may be partial or complete loss of movement or sensation. Nerve pain may be severe and persist for a prolonged period of time.

• Partial or complete loss of hand movement
• Partial or complete loss of sensation in the fingers
• Recurrent or unnoticed injury to the hand

Call your health care provider if symptoms of distal median nerve dysfunction are present. Early diagnosis and treatment increase the chance of controlling symptoms.

Prevention varies depending on the cause. In patients with underlying diabetes, controlling blood sugar may reduce the risk of developing nerve disorders.

In occupations that require repetitive wrist movements, a change in the way the job is performed may be necessary. Frequent breaks in activity, "wrist rests" on keyboards, and other measures may reduce the risk of distal median nerve dysfunction. When possible, avoid prolonged repetitive movement of the wrist.

Neuropathy - distal median nerve

Scholten RJ, Mink van der Molen A, Uitdehaag BM, Bouter LM, de Vet HC. Surgical treatment options for carpal tunnel syndrome. Cochrane Database Syst Rev. 2007;(4):CD003905.

Piazzini DB, Aprile I, Ferrara PE, et al. A systematic review of conservative treatment of carpal tunnel syndrome. Clin Rehabil. 2007;21(4):299-314.

Updated by: Sean O. Stitham, MD, private practice in Internal Medicine, Seattle, Washington; and Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.