Peripheral Neuropathy

WhatIs Peripheral Neuropathy?
The name of the condition tells you a bit about what it is:
Peripheral: Beyond (in this case, beyond the brain and the spinal cord.)
Neuro-: Related to the nerves
-pathy: Disease
Peripheral neuropathy refers to the conditions that result when nerves that carry
messages to and from the brain and spinal cord from and to the rest of the body are
damaged or diseased.
The peripheral nerves make up an intricate network that connects the brain and spinal
cord to the muscles, skin, and internal organs. Peripheral nerves come out of the spinal
cord and are arranged along lines in the body called dermatomes. Typically, damage to
a nerve will affect one or more dermatomes, which can be tracked to specific areas of
the body. Damage to these nerves interrupts communication between the brain and
other parts of the body and can impair muscle movement, prevent normal sensation in
the arms and legs, and cause pain.
Types of Peripheral Neuropathy
There are several different kinds of peripheral neuropathies that stem from a variety of
causes. They range from carpal tunnel syndrome (a traumatic injury common after
chronic repetitive use of the hands and wrists, such as with computer use) to nerve
damage linked to diabetes.
As a group, peripheral neuropathies are common, especially among people over the
age of 55. All together, the conditions affect 3% to 4% of people in this group.
Neuropathies are typically classified according to the problems they cause or what is at
the root of the damage. There also are terms that express how extensively the nerves
have been damaged.
Mononeuropathy
Damage to a single peripheral nerve is called mononeuropathy. Physical injury or
trauma such as from an accident is the most common cause. Prolonged pressure on a
nerve, caused by extended periods of being sedentary (such as sitting in a wheelchair
or lying in bed), or continuous, repetitive motions, can trigger a mononeuropathy.
Carpal tunnel syndrome is a common type of mononeuropathy. It is called an overuse
strain injury, which occurs when the nerve that travels through the wrist is compressed.
People whose work requires repeated motions with the wrist (such as assembly-line
workers, physical laborers, and those who use computer keyboards for prolonged
periods) are at greater risk.
The damage to the nerve can result in numbness, tingling, unusual sensations, and
pain in the first three fingers on the thumb side of the hand. The person may awaken at
night with numbness in their hand or discover that when they perform activities like
using a hair dryer, the numbness is more noticeable. In time, carpal tunnel injuries can
weaken the muscles in the hand. You may also feel pain, tingling, or burning in your
arm and shoulder.
Here are examples of other mononeuropathies that can cause weakness in the
affected parts of the body, such as hands and feet:
Ulnar nerve palsy occurs when the nerve that passes close to the surface of the
skin at the elbow is damaged. The numbness is noted in the 4th and 5th digit of
the hand.
Radial nerve palsy is caused by injury to the nerve that runs along the
underside of the upper arm and can occur with fractures of the humerus bone in
the upper part of the arm.
Peroneal nerve palsy results when the nerve at the top of the calf on the outside
of the knee is compressed. This leads to a condition called "foot drop," in which it
becomes difficult to lift the foot.
Neuropathy can affect nerves that control muscle movement (motor nerves) and those
that detect sensations such as coldness or pain (sensory nerves). In some cases, it
can affect internal organs, such as the heart, blood vessels, bladder, or intestines.
Neuropathy that affects internal organs is called an autonomic neuropathy. This rare
condition can cause low blood pressure or problems with sweating.
Polyneuropathy
Polyneuropathy accounts for the greatest number of peripheral neuropathy cases. It
occurs when multiple peripheral nerves throughout the body malfunction at the same
time. Polyneuropathy can have a wide variety of causes, including exposure to certain
toxins such as with alcohol abuse, poor nutrition (particularly vitamin B deficiency), and
complications from diseases such as cancer or kidney failure.
One of the most common forms of chronic polyneuropathy is diabetic neuropathy, a
condition that occurs in people with diabetes. It is more severe in people with poorly
controlled blood sugar levels. Though less common, diabetes can also cause a
mononeuropathy.
The most common symptoms of polyneuropathy are:
Tingling
Numbness
Loss of sensation in the arms and legs
A burning sensation in the feet or hands
Because people with chronic polyneuropathy often lose their ability to sense
temperature and pain, they can burn themselves and develop open sores as the result
of injury or prolonged pressure. If the nerves serving the organs are involved, diarrhea
or constipation may result, as well as loss of bowel or bladder control. Sexual
dysfunction and abnormally low blood pressure also can occur.
One of the most serious polyneuropathies is Guillain-Barre syndrome, a rare disease
that strikes suddenly when the body's immune system attacks nerves in the body just
as they leave the spinal cord. Symptoms tend to appear quickly and worsen rapidly,
sometimes leading to paralysis. Early symptoms include weakness and tingling that
eventually may spread upward into the arms. Blood pressure problems, heart rhythm
problems, and breathing difficulty may occur in the more severe cases. However,
despite the severity of the disease, recovery rates are good when patients receive
treatment early.
Chronic inflammatory demyelinating polyneuropathy is a chronic form of Guillian-Barre
where the symptoms continue for months and even years. Early diagnosis and
treatment is crucial for CIDP patients, 30% of which risk eventually being confined to a
wheelchair.
What Causes Peripheral Neuropathy?
There are many factors that can cause peripheral neuropathies, so it is often difficult to
pinpoint the origin. Neuropathies occur by one of three methods:
Acquired neuropathies are caused by environmental factors such as toxins,
trauma, illness, or infection. Known causes of acquired neuropathies include:
Diabetes
Several rare inherited diseases
Alcoholism
Poor nutrition or vitamin deficiency
Certain kinds of cancer and chemotherapy used to treat them
Conditions where nerves are mistakenly attacked by the body’s own immune
system or damaged by an overaggressive response to injury
Certain medications
Kidney or thyroid disease
Infections such as Lyme disease, shingles, or AIDS
Hereditary neuropathies are not as common. Hereditary neuropathies are
diseases of the peripheral nerves that are genetically passed from parent to child.
The most common of these is Charcot-Marie-Tooth disease type 1. It is
characterized by weakness in the legs and, to a lesser degree, the arms --
symptoms that usually appear between mid-childhood and age 30. This disease
is caused by degeneration of the insulation that normally surrounds the nerves
and helps them conduct the electrical impulses needed for them to trigger muscle
movement.
Idiopathic neuropathies are from an unknown cause. As many as one-third of
all neuropathies are classified in this way.