What Is 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.
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.
- 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 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.