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

• "Peripheral" means nerves beyond the brain and spinal cord.
• "Neuro" means nerves.
• "Pathy" means abnormal.

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

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 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 (diabetic neuropathy)
  • Dietary deficiencies (especially vitamin B-12)
  • Excessive alcohol use (alcoholic neuropathy)
  • Uremia (from kidney failure)
  • Cancer
• Infectious or inflammatory conditions
  • 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 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 and blood flow)
  • Prolonged exposure to cold temperature

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.

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.

The 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, 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.

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 (such as being 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
• 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

A detailed history will be needed to determine the cause of the neuropathy. Neurologic examination may reveal abnormalities of movement, sensation, or organ function. (See also entries on the specific nerve dysfunction.) Changes in reflexes and muscle bulk may also be present.

Tests that reveal neuropathy may include:

• 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.