Neuropathy - distal median nerve

Alternative names
Distal median nerve dysfunction

Definition

Distal median nerve dysfunction is a form of peripheral neuropathy (nerve dysfunction outside the central nervous system) affecting movement of or sensation in the hand, caused by damage to the distal median nerve.

For a common form, see carpal tunnel syndrome.

Causes, incidence, and risk factors
Dysfunction of a single nerve group, such as the distal median nerve, is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although occasionally systemic disorders may cause isolated nerve damage (such as the damage that occurs with mononeuritis multiplex).

Distal median nerve dysfunction occurs when the nerve is injured by trauma, entrapment, or inflammation. Entrapment involves pressure on the nerve where it passes through a narrow structure. Wrist fractures may injure the median nerve directly or may present a risk for entrapment of the nerve later on.

The nerve can also be compressed at the wrist by tendonitis, arthritis, or conditions that affect connective tissue or cause deposits in the tissues (such as multiple myeloma, pregnancy, acromegaly, and hypothyroidism). These mechanical factors may cause nerve disease, blocking blood flow to the area.

In some cases, no detectable cause can be identified.

Carpal tunnel syndrome, a form of median nerve dysfunction, is one of the more common localized peripheral neuropathies. Carpal tunnel syndrome may be associated with entrapment of the nerve following prolonged or repeated pressure on the wrist area (such as may occur with repetitive wrist movements such as those made when typing or using a computer). This is a fairly common occupational or recreational injury.

Symptoms

     
  • Sensation changes of the thumb and first 2 fingers       o Numbness, decreased sensation       o Tingling, burning sensation       o Waking up at night with wrist or hand pain (may be severe)  
  • Weakness of the hand       o Dropping things       o Difficulty grasping objects

Signs and tests
Examination may show decreased sensation in the thumb side (radial) fingers of the hand. There may be weakness of the thumb and difficulty using it to pinch.

Tests that reveal distal median nerve dysfunction may include:

     
  • EMG (a recording of electrical activity in muscles)  
  • 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, scans, or other tests and procedures.

Treatment

Treatment is aimed at correcting the underlying cause. In most cases, isolated median nerve dysfunction is due to entrapment or injury. If so, identifying the site of entrapment is best done with EMG or in some cases, X-rays and MRI scans. If an entrapment is confirmed, medications and even surgery may be helpful, depending on the site of entrapment and severity of nerve injury.

If the median nerve is affected by carpal tunnel syndrome, a wrist splint can reduce further injury to the nerve and help alleviate symptoms. In some cases, no treatment is required and recovery is spontaneous. 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 like 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 and may include braces, splints, or other appliances. Vocational counseling, occupational therapy, occupational changes, job retraining, or similar interventions may be recommended.

Expectations (prognosis)
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.

Complications

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

Calling your health care provider
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

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.

Johns Hopkins patient information

Last revised: December 4, 2012
by Amalia K. Gagarina, M.S., R.D.

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