Peripheral neuropathy is a problem with the nerves that carry information to and from the brain and spinal cord. This can produce pain, loss of sensation, and an inability to control muscles.

• "Peripheral" means nerves further out from the center of the body, distant from the brain and spinal cord.
• "Neuro" means nerves.
• "Pathy" means abnormal.

One set of peripheral nerves relay information from your central nervous system (brain and spinal cord) to muscles and other organs. A second set relays information from your skin, joints, and other organs back to your brain.

Peripheral neuropathy occurs when these nerves don't work properly, resulting in pain, loss of sensation, inability to control muscles, and other possible problems.

In some cases, the failure of nerves that control blood vessels, intestines, and other organs results in abnormal blood pressure, digestion problems, and loss of other basic body processes. Peripheral neuropathy may involve damage to a single nerve or nerve group (mononeuropathy) or may affect multiple nerves (polyneuropathy).

There are numerous reasons for nerves to malfunction. In many cases, no cause can be identified. Damage to nerves can result from:

• Diseases that run in families (hereditary disorders) such as:
  • Charcot-Marie-Tooth disease
  • Friedreich's ataxia
• Diseases that affect the whole body (systemic or metabolic disorders) such as:
  • Diabetes (diabetic neuropathy)
  • Dietary deficiencies (especially vitamin B-12)
  • Excessive alcohol use (alcoholic neuropathy)
  • Uremia (from kidney failure)
  • Cancer
• Infections or inflammation, including:
  • AIDS
  • Hepatitis
  • Colorado tick fever
  • Diphtheria
  • Guillain-Barre syndrome
  • HIV infection without development of AIDS
  • Leprosy
  • Lyme disease
  • Polyarteritis nodosa
  • Rheumatoid arthritis
  • Sarcoidosis
  • Sjogren syndrome
  • Syphilis
  • Systemic lupus erythematosus
  • Amyloidosis
• Exposure to poisonous substances such as:
  • Sniffing glue or other toxic compounds
  • Nitrous oxide
  • Industrial chemicals -- especially solvents
  • Heavy metals (lead, arsenic, mercury, etc.)
• Neuropathy secondary to drugs (many drugs, including some used for chemotherapy, can cause neuropathy)
• Miscellaneous causes
  • Compression of a nerve by casts, splints, braces, crutches, or other devices
  • Decreased oxygen and blood flow (ischemia)
  • Direct injury of the nerve either by hitting the nerve
  • Prolonged exposure to cold temperature
  • Prolonged pressure on the nerve (such as a long surgery or lengthy illness)

Peripheral neuropathy is very common. Because there are numerous types and causes of neuropathy and scientists don't always agree on the same definition of neuropathy, the exact incidence cannot be determined precisely.

Some people have a hereditary predisposition for neuropathy.

The symptoms depend on which type of nerve is affected. The three main types of nerves are:

• Those that carry sensations (sensory)
• Those that control muscles (motor)
• Those that carry information to organs and glands (autonomic)

Neuropathy can affect any one or a combination of all three types of nerves. Symptoms also depend on whether the condition affects the whole body or just one nerve (as from an injury).

Longer nerves are more easily injured than shorter ones, so it is common for you to have worst symptoms in the legs and feet than in the hands and arms.

SENSATION CHANGES

Damage to sensory fibers results in changes in sensation, burning sensations, nerve pain, tingling or numbness, or an inability to determine joint position, which causes incoordination.

For many neuropathies, sensation changes often begin in the feet and progress toward the center of the body with involvement of other areas as the condition worsens. Diabetes is a common cause for sensory neuropathy.

MOVEMENT DIFFICULTIES

Damage to the motor fibers interferes with muscle control and can cause weakness, loss of muscle bulk, and loss of dexterity. Sometimes, cramps are a sign of motor nerve involvement.

Other muscle-related symptoms include:

• Difficulty breathing or swallowing
• Difficulty or inability to move a part of the body (paralysis)
• Falling (from legs buckling or tripping over toes)
• Lack of dexterity (such as being unable to button a shirt)
• Lack of muscle control
• Loss of muscle tissue (muscle atrophy)
• Muscle twitching or cramping

AUTONOMIC SYMPTOMS

The autonomic nerves control involuntary or semi-voluntary functions, such as control of internal organs and blood pressure. Damage to autonomic nerves can cause:

• Abdominal bloating
• Blurred vision
• Constipation
• Decreased ability to sweat
• Diarrhea
• Difficulty beginning to urinate (urinary hesitancy)
• Dizziness that occurs when standing up or fainting associated with a fall in blood pressure
• Feeling full after eating a small amount (early satiety)
• Feeling of incomplete bladder emptying
• Heat intolerance with exertion
• Male impotence
• Nausea or vomiting after meals
• Unintentional weight loss (more than 5% of body weight)
• Urinary incontinence

A detailed history will be needed to determine the cause of the neuropathy. A neurological exam may reveal problems with movement, sensation, or organ function. Changes in reflexes and muscle bulk may also be present.

Blood tests may be done to screen for medical conditions such as diabetes and vitamin deficiencies.

Tests that reveal neuropathy may include:

• EMG (a recording of electrical activity in muscles)
• Nerve conduction tests
• Nerve biopsy

Tests for neuropathy are guided by the suspected cause of the disorder, as suggested by the history, symptoms, and pattern of symptom development. They may include various blood tests, x-rays, scans, or other tests and procedures.

Treatmet involves:

• Identifying and treating any underlying medical problem (such as diabetes) or removing the cause (such as alcohol)
• Controlling symptoms
• Curing the disorder, if possible
• Helping the patient gain maximum independence and self-care ability

Physical therapy, occupational therapy, and orthopedic interventions may be recommended. For example, exercises and retraining may be used to increase muscle strength and control. Wheelchairs, braces, and splints may improve mobility or the ability to use an affected arm or leg.

Safety is an important consideration for people with neuropathy. Lack of muscle control and reduced sensation increase the risk of falls and other injuries. The person may not notice a potential source of injury because he or she can't feel it. For example, one may not notice if water in a bathtub is too hot. For this reason, people with decreased sensation should check their feet or other affected areas frequently for bruises, open skin areas, or other injuries, which may go unnoticed and become severely infected. Often, a podiatrist can determine if special orthotic devices are needed.

Safety measures for people experiencing difficulty with movement may include:

• Installing railings
• Removing obstacles on floors such as loose rugs

Safety measures for people having difficulty with sensation include:

• Adequate lighting (including night lights)
• Testing water temperature before bathing
• Use of protective shoes (no open toes, no high heels)

Shoes should be checked often for grit or rough spots that may cause injury to the feet.

Persons with neuropathy (especially those with polyneuropathy or mononeuropathy multiplex) are prone to new nerve injury at pressure points such as knees and elbows. They should avoid prolonged pressure on these areas from leaning on the elbows, crossing the knees, or assuming similar positions.

Prescription pain medications may be needed to control nerve pain. Anticonvulsants (phenytoin, carbamazepine, gabapentin, and pregabalin), tricyclic antidepressants (duloxetine), or other medications may be used to reduce the stabbing pains. Use the lowest dose possible to avoid side effects.

Adjusting position, using frames to keep bedclothes off tender body parts, or other measures may also be helpful to reduce pain.

The symptoms of autonomic changes may be difficult to treat or respond poorly to treatment.

• Use of elastic stockings and sleeping with the head elevated may help treat low blood pressure that occurs when standing up (postural hypotension). Fludrocortisone or similar medications may also be helpful.
• Medications that increase gastric motility (such as metoclopramide), eating small frequent meals, sleeping with the head elevated, or other measures may help.
• Manual expression of urine (pressing over the bladder with the hands), intermittent catheterization, or medications such as bethanechol may be necessary for those with bladder dysfunction.
• Impotence, diarrhea, constipation or other symptoms are treated as appropriate.

Additional information can be obtained from the Neuropathy Association - www.neuropathy.org

The outcome greatly depends on the cause of the neuropathy. In cases where a medical condition can be identified and treated, the outlook may be excellent. However, in severe neuropathy, nerve damage can be permanent, even if the cause is treated appropriately.

For most hereditary neuropathies, there is no cure. Some of these conditions are harmless, while others progress more rapidly and may lead to permanent, severe complications.

The inability to feel or notice injuries can lead to infection or structural damage. Changes include poor healing, loss of tissue mass, tissue erosions, scarring, and deformity. Other complications include:

• Decreased self esteem
• Difficulty breathing
• Difficulty swallowing
• Irregular heart rhythms ( arrhythmias)
• Need for amputation
• Partial or complete loss of movement or control of movement
• Partial or complete loss of sensation
• Relationship problems related to impotence
• Recurrent or unnoticed injury to any part of the body

Call your health care provider if symptoms of peripheral neuropathy are present. In all cases, early diagnosis and treatment increases the possibility that symptoms can be controlled.

Nerve pain, such as that caused by peripheral neuropathy, can be difficult to control. If pain is severe, contact a pain specialist may be able to suggest different approaches.

Emergency symptoms include irregular or rapid heartbeats, difficulty breathing, difficulty swallowing, and fainting.

If a prolonged procedure or immobility is expected, appropriate measures (such as padding vulnerable areas) can be taken beforehand to reduce the risk of nerve problems.

Persons with a hereditary predisposition for neuropathy need to be especially careful to limit alcohol and manage other medical problems closely.

All people can reduce the risk of neuropathy by following a balanced diet, drinking alcohol in moderation, and maintaining good control of diabetes and other medical problems, if present.

Shy ME. Peripheral neuropathies. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 446.