Distal median nerve dysfunction

Definition

Distal median nerve dysfunction is a form of peripheral neuropathy that affects the movement of or sensation in the hands.

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

Alternative Names

Neuropathy - distal median nerve

Causes

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.

Distal median nerve dysfunction occurs when the nerve is inflamed, trapped, or injured by trauma. 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. Diabetes can make this condition worse.

Symptoms

• Pain in the wrist or hand that wakes you up at night
  • May be severe
  • Pain may be felt in other areas, for example in the upper arm (this is called referred pain)
• Sensation changes in the thumb and pointer (index), middle, and part of the ring fingers, such as:
  • Burning feeling
  • Decreased sensation
  • Numbness
  • Tingling
• Weakness of the hand that causes you to:
  • Drop things
  • Have difficulty grasping objects or buttoning a shirt

Exams and Tests

Your doctor will examine your wrist and ask questions about your medical history. The 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

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 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

Outlook (Prognosis)

If the cause of the nerve dysfunction can be identified and successfully treated, there is a good chance 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.

Possible Complications

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

When to Contact a Medical Professional

Call your health care provider if you have symptoms of distal median nerve dysfunction. Early diagnosis and treatment increase the chance of curing or controlling symptoms.

Prevention

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.

References

Jarvik JG, Comstock BA, Kliot M, et al. Surgery versus non-surgical therapy for carpal tunnel syndrome: a randomized parallel-group trial. Lancet.2009 Sep 26;374(9695):1074-81.

Katirji B, Koontz D. Disorders of peripheral nerves. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, Pa: Saunders Elsevier; 2012:chap 76.

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