Peripheral neuropathy is failure of the nerves that carry information to and from the brain and spinal cord. This produces symptoms like pain, loss of sensation, and inability to control muscles.

("Neuro" = nerves, "pathy" = abnormal; "peripheral" = nerves beyond the brain and spinal cord.)

The peripheral nerves are responsible for relaying information from your central nervous system (brain and spinal cord) to muscles and other organs. Peripheral nerves also relay information back to your spinal cord and brain from your skin, joints, and other organs. Peripheral neuropathy occurs when these nerves fail to function properly, resulting in loss of sensation, pain, or inability to control muscles.

In some cases, failure of nerves controlling blood vessels, intestinal function, and other organs results in abnormal blood pressure, digestion, and loss of other basic involuntary processes. Peripheral neuropathy may involve damage to a single nerve or nerve group (mononeuropathy) or may affect multiple nerves (polyneuropathy).

There are numerous reasons why nerves may not function properly. In some cases, no cause can be identified. Damage to nerves can result from one of the specific conditions associated with neuropathy including:

• Hereditary disorders
  • Charcot-Marie-Tooth disease
  • Friedreich's ataxia
• Systemic or metabolic disorders
  • diabetes mellitus (diabetic neuropathy)
  • dietary deficiencies (especially vitamin B12)
  • excessive use of alcohol (alcoholic neuropathy)
  • uremia (from kidney failure)
  • Cancer
• Infectious or inflammatory conditions
  • AIDS
  • Hepatitis
  • botulism
  • Colorado tick fever
  • diphtheria
  • Guillain-Barre syndrome
  • HIV infection without development of AIDS
  • leprosy
  • Lyme
  • polyarteritis nodosa
  • rheumatoid arthritis
  • sarcoidosis
  • syphilis
  • systemic lupus erythematosus
  • amyloid
• Exposure to toxic compounds
  • sniffing glue or other toxic compounds
  • nitrous oxide
  • industrial agents--especially solvents
  • heavy metals (lead, arsenic, mercury, etc.)
• Neuropathy secondary to drugs (many drugs can cause neuropathy)
• Miscellaneous causes
  • ischemia (decreased oxygen/decreased blood flow)
  • prolonged exposure to cold temperature

Peripheral neuropathy is very common. Because there are numerous types and causes of neuropathy, the incidence varies greatly, depending on the type of neuropathy, geographic region, and many other factors. As scientists don't always agree on the same definition of neuropathy, the exact incidence can not be determined precisely.

Risk factors for neuropathy include diabetes, heavy alcohol use, and exposure to certain chemicals and drugs. Some people have a hereditary predisposition for neuropathy. Prolonged pressure on a nerve is another risk for developing a nerve injury. Pressure injury may be caused by prolonged immobility (such as a long surgical procedure or lengthy illness) or compression of a nerve by casts, splints, braces, crutches, or other devices.

Symptoms depend on which type of nerve is affected. The three main types of nerves are sensory, motor, and 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).

SENSATION CHANGES

Damage to sensory fibers results in changes in sensation, ranging from abnormal sensations (burning, nerve pain, or tingling), numbness , or an inability to determine joint position in the area, 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.

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:

• lack of muscle control
• difficulty or inability to move a part of the body (paralysis)
• muscle atrophy
• muscle twitching (fasciculation) or cramping
• difficulty breathing or swallowing
• falling (from legs buckling or tripping over toes)
• lack of dexterity (i.e. unable to button a shirt)

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:

• blurred vision
• decreased ability to sweat (anhidrosis)
• dizziness that occurs when standing up or fainting associated with a fall in blood pressure
• heat intolerance with exertion (decreased ability to regulate body temperature)
• nausea or vomiting after meals
• abdominal bloating (swelling)
• feeling full after eating a small amount (early satiety)
• diarrhea
• constipation
• unintentional weight loss (more than 5% of body weight)
• urinary incontinence
• feeling of incomplete bladder emptying
• difficulty beginning to urinate (urinary hesitancy)
• male impotence

• EMG (a recording of electrical activity in muscles)
• Nerve conduction tests
• Nerve biopsy
• Blood tests to screen for medical conditions, such as diabetes and vitamin deficiency, among others.

The goal of treatment may be to identify and treat the underlying cause, cure the disorder (if possible), give the patient maximum independence and self-care ability; and/or control the symptoms. As a rule, treatment of the underlying medical problem (e.g., diabetes) or removal of a causative agent (e.g., alcohol) are the first steps.

Physical therapy, vocational therapy, occupational therapy, and orthopedic interventions may be recommended to promote self care ability and independence. For example, exercises and retraining may be used to increase muscle strength and control. Appliances such as wheelchairs, braces, and splints may improve mobility or ability to use an affected extremity.

Safety is an important consideration for people with neuropathy. Lack of muscle control or decreased sensation increase the risk of falls or other injuries. The person may not notice a potential source of injury because he or she can't feel it. 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 (because there is no pain) 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 railings, various appliances, removal of obstacles (such as loose rugs that may slip on the floor), and other measures as appropriate. Safety measures for people having difficulty with sensation include adequate lighting (including lights left on at night), testing water temperature before bathing or immersing the body in water, use of protective shoes (no open toes, no high heels, and so on) and similar measures. Shoes should be checked often for grit or rough spots that may cause injury to the feet.

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

Over-the-counter analgesics or prescription pain medications may be needed to control nerve pain. Anticonvulsants (phenytoin, carbamazepine, gabapentin), tricyclic antidepressants or various other medications may be used to reduce the stabbing pains that some people experience. Whenever possible, medication use should be minimized to avoid side effects.

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

Autonomic changes may be treated symptomatically. They may be difficult to treat or respond poorly to treatment.

• Postural hypotension -- use of elastic stockings and sleeping with the head elevated may help. Fludrocortisone or similar medications may be beneficial in reducing postural hypotension for some people.
• Reduced gastric motility -- medications that increase gastric motility (such as metoclopramide), eating small frequent meals, sleeping with the head elevated, or other measures may help.
• Bladder dysfunction -- manual expression of urine (pressing over the bladder with the hands), intermittent catheterization, or medications such as bethanechol may be necessary.
• Impotence, diarrhea, constipation or other symptoms are treated as appropriate.

Additional information can be obtained from the http://www.neuropathy.org/Neuropathy Association.

The outcome greatly depends on the cause of the neuropathy. In cases where a medical condition can be identified and treated, the prognosis 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 have a benign (harmless) prognosis, 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 ulcer formation, poor healing, loss of tissue mass, scarring, and deformity. Other complications include:

• partial or complete loss of movement (or control of movement)
• partial or complete loss of sensation
• difficulty breathing
• difficulty swallowing
• cardiac arrhythmias (uncommon)
• decreased self esteem
• relationship problems related to impotence
• recurrent or unnoticed injury to any part of the body

If a prolonged procedure or immobility is expected, appropriate measures (such as padding vulnerable areas) can done beforehand to reduce this risk.

Some people have a hereditary predisposition for neuropathy. Such people need to be especially careful to limit alcohol and manage other medical problems closely.

All people can reduce the risk of neuropathy through a balanced diet, limited exposure to alcohol, and maintaining good control of diabetes and other medical problems, if present.