neuropathy - distal median nerve
A form of peripheral neuropathy (disease
of the nerves) involving impaired movement and/or sensation of the thumb
caused by damage to the distal median nerve.
Causes, Incidence and Risk Factors
Distal median nerve dysfunction occurs
when there is damage to the distal portion of the median nerve, which travels
down the arm and provides movement and sensation to the thumb. (The distal
portion is the part closest to the hand.) Carpal tunnel syndrome, another
form of median nerve dysfunction, is one of the more common peripheral
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 occurs with mononeuritis
multiplex). The usual causes are direct trauma, prolonged pressure on the
nerve, and compression of the nerve by nearby body structures. Entrapment
involves pressure on the nerve where it passes through a narrow structure.
Wrist fractures may injure the median
nerve. The nerve may be compressed at the wrist because of tendonitis,
arthritis, or conditions that affect connective tissue or cause deposits
in the tissues (such as multiple myeloma, pregnancy, acromegaly, and hypothyroidism).
In some cases, no detectable cause can be identified. These mechanical
factors may be complicated by lack of oxygen from decreased blood flow
(ischemia) in the area.
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). This
is a fairly common occupational or recreational injury.
sensation changes of the first 3 fingers
Signs And Tests
numbness, decreased sensation
tingling, burning sensation
pain (may be severe)
weakness of the hand
difficulty grasping objects
Neuromuscular examination of the hand
and wrist indicates distal median nerve dysfunction. There may be decreased
sensation in the thumb side (radial) fingers. There may be weakness of
the thumb and difficulty with opposition of the thumb and little finger.
A detailed history may be needed to determine the possible cause of the
Tests that reveal distal median nerve
dysfunction may include:
Tests are guided by the suspected cause of
the dysfunction as suggested by the history, symptoms presented, and pattern
of symptom development. They may include various blood tests, X-rays, scans,
or other tests and procedures.
An EMG (a recording of electrical activity
nerve conduction tests
a nerve biopsy (rarely needed)
Treatment is aimed at maximizing independence
and ability to function at work and home. The cause should be identified
and treated as appropriate. In some cases, no treatment is required and
recovery is spontaneous.
If there is no history of trauma to the
area, conservative treatment is indicated by sudden onset, minimal sensation
changes and no difficulty in movement, and no test results indicating degeneration
of the nerve axon (nerve fiber). Corticosteroids injected into the area
may reduce swelling and pressure on the nerve in some cases.
Surgical intervention is indicated if
the disorder is chronic (long term) or symptoms are worsening, if there
is difficulty with movement, or if there is test evidence that nerve axon
degeneration is present. Surgical decompression may be recommended if the
symptoms are caused by entrapment of the nerve. Surgical removal of lesions
that press on the nerve may benefit some cases.
CONTROL OF SYMPTOMS:
Over-the-counter or prescription analgesics
may be needed to control pain (neuralgia). Other medications, including
phenytoin, carbamazepine, or tricyclic antidepressants such as amitriptyline,
may reduce the stabbing pains that some persons experience. Whenever possible,
their use should be avoided or minimized to reduce the risk of developing
medication side effects.
Physical therapy exercises may be appropriate
for some persons to maintain muscle strength. Orthopedic assistance may
maximize the ability to use the hand. This may include use of braces, splints,
or other appliances. Vocational counseling, occupational therapy, occupational
changes, job retraining, or similar interventions may be recommended.
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, resulting in various extent of disability. Nerve pain may
be severe and persist for a prolonged period of time.
Calling Your Health Care Provider
partial or complete loss of hand movement
partial or complete loss of sensation in the
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.
Avoid prolonged repetitive movement of the wrist.
In occupations that require repetitive
wrist movements, change in the way the job is performed may be necessary.
Frequent breaks in activity, "wrist rests" on keyboards, or other measures
may reduce the risk of distal median nerve dysfunction.