What is peripheral neuropathy?

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What is peripheral neuropathy?

Peripheral neuropathy is a common neurological disorder in the

nerves outside the central nervous system which begins with a burning pain and a

tingling feeling in the feet and fingertips. The condition can subsequently

expand to other regions, including internal organs, and in a later stage can

develop into arm and leg muscle weakness. Peripheral neuropathy is a widespread

disorder, and there are many underlying causes. Some of these causes are common,

such as diabetes, and others are extremely rare, such as acrylamide poisoning

and certain inherited disorders. The most

common worldwide cause of peripheral neuropathy is leprosy. Leprosy

is caused by the bacterium Mycobacterium leprae, which attacks the peripheral

nerves of affected people. According to statistics gathered by the World Health

Organization, an estimated 1.15 million people suffer from leprosy worldwide.

Leprosy is extremely rare, where diabetes is the most commonly known cause of

peripheral neuropathy. It has been estimated that more than 17 million people in

the United States and Europe suffer from diabetes-related polyneuropathy. Many

neuropathies are idiopathic, meaning that no known cause can be found. The most

common of the inherited peripheral neuropathies in the United States is

Charcot-Marie-Tooth disease, which affects approximately 125,000 persons.

Another of the better known peripheral neuropathies is

Guillain-Barré syndrome, which arises from complications associated with viral

illnesses, such as cytomegalovirus, Epstein-Barr virus, and human

immunodeficiency virus (HIV), or bacterial infection, including Campylobacter

jejuni and Lyme disease. The worldwide incidence rate is approximately 1.7 cases

per 100,000 people annually. Other well-known causes of peripheral neuropathies

include chronic alcoholism, infection varicella-zoster virus, botulism, and

poliomyelitis. Peripheral neuropathy may develop as a primary symptom, or it may

be due to another disease. For example, peripheral neuropathy is only one

symptom of diseases such as amyloid neuropathy, certain cancers, or inherited

neurologic disorders. Such diseases may affect the peripheral nervous system

(PNS) and the central nervous system (CNS), as well as other body tissues.

Nerve cells are the basic building block of the nervous system. In

the PNS, nerve cells can be threadlike--their width is microscopic, but their

length can be measured in feet. The long, spidery extensions of nerve cells are

called axons. When a nerve cell is stimulated, by touch or pain, for example,

the message is carried along the axon, and neurotransmitters are released within

the cell. Neurotransmitters are chemicals within the nervous system that direct

nerve cell communication.

Certain nerve cell axons, such as the ones in the PNS, are covered

with a substance called myelin. The myelin sheath may be compared to the plastic

coating on electrical wires--it is there both to protect the cells and to

prevent interference with the signals being transmitted. Protection is also

given by Schwann cells, special cells within the nervous system that wrap around

both myelinated and unmyelinated axons. The effect is similar to beads threaded

on a necklace. erve cell axons leading to the same areas of the body may be

bundled together into nerves. Continuing the comparison to electrical wires,

nerves may be compared to an electrical cord--the individual components are

coated in their own sheaths and then encased together inside a larger protective

covering.

The nervous system is classified into two parts: the CNS and the

PNS. The CNS is made up of the brain and the spinal cord, and the PNS is

composed of the nerves that lead to or branch off from the CNS. he peripheral

nerves handle a diverse array of functions in the body. This diversity is

reflected in the major divisions of the PNS--the afferent and the efferent

divisions. The afferent division is in charge of sending sensory information

from the body to the CNS. When afferent nerve cell endings called receptors are

stimulated, they release neurotransmitters. These neurotransmitters relay a

signal to the brain, which interprets it and reacts by releasing other

neurotransmitters.

Some of the neurotransmitters released by the brain are directed at

the efferent division of the PNS. The efferent nerves control voluntary

movements, such as moving the arms and legs, and involuntary movements, such as

making the heart pump blood. The nerves controlling voluntary movements are

called motor nerves, and the nerves controlling involuntary actions are referred

to as autonomic nerves. The afferent and efferent divisions continually interact

with each other. For example, if a person were to touch a hot stove, the

receptors in the skin would transmit a message of heat and pain through the

sensory nerves to the brain. The message would be processed in the brain and a

reaction, such as pulling back the hand, would be transmitted via a motor nerve.

When an individual suffers from a peripheral neuropathy, nerves of

the PNS have been damaged. Nerve damage can arise from a number of causes, such

as disease, physical injury, poisoning, or malnutrition. These agents may affect

either afferent or efferent nerves. Depending on the cause of damage, the nerve

cell axon, its protective myelin sheath, or both may be injured or destroyed.

Peripheral neuropathy often affects people with diabetes and

autoimmune diseases such as rheumatoid arthritis and lupus. Certain vitamin

deficiencies, some medications and alcoholism can also damage peripheral nerves.

The areas of the body most commonly affected by peripheral neuropathy are the

feet and lower and upper legs, although the hands and outer arms can also be

affected with this type of nerve damage. Neuropathy in the feet can result in a

loss of foot sensation, increasing the risk of foot problems.

Treating the underlying condition may relieve some cases of

peripheral neuropathy. In other cases, treatment may focus on managing pain.

Peripheral nerves have a remarkable ability to regenerate themselves, and new

treatments using nerve growth factors or gene therapy may offer even better

chances for recovery in the future. Therapy for peripheral neuropathy differs

depending on the cause. For example, therapy for peripheral neuropathy caused by

diabetes involves control of the diabetes. In cases where a tumor or ruptured

disc is the cause, therapy may involve surgery to remove the tumor or to repair

the ruptured disc. In entrapment or compression neuropathy treatment may consist

of splinting or surgical decompression of the ulnar or median nerves. Peroneal

and radial compression neuropathies may require avoidance of pressure. Physical

therapy and/or splints may be useful in preventing contractures (a condition in

which shortened muscles around joints cause abnormal and sometimes painful

positioning of the joints).

Recovery from peripheral neuropathy is usually slow. Depending on

the type of peripheral neuropathy, the patient may fully recover without

residual effects or may partially recover and have sensory, motor, and vasomotor

(blood vessel) deficits. If severely affected, the patient may develop chronic

muscular atrophy.