Understanding Peripheral Neuropathy -- the Basics
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.
Radial nerve palsy is caused by injury to the nerve that runs along the underside of the arm.
Peroneal nerve palsy results when the nerve at the top of the calf behind the knee is compressed. This leads to a condition called "foot drop," in which it becomes difficult to lift the front of one or both feet.
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.
Polyneuropathy accounts for the greatest number of peripheral neuropathy cases. It occurs when many peripheral nerves throughout the body malfunction at the same time. Polyneuropathy can have a wide variety of causes, including exposure to certain toxins, 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 the result of poorly controlled blood sugar levels. Though less common, diabetes can also cause mononeuropathy, often characterized by weakness of the eye or of the thigh muscles.
These are the most common symptoms of polyneuropathy:
- Loss of sensation in the arms and legs
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.
Joints are particularly vulnerable to stress in people with polyneuropathy because they are often insensitive to pain.
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. Symptoms tend to appear quickly and worsen rapidly, sometimes leading to paralysis. Early symptoms include weakness, tingling, and loss of sensation in the legs that eventually spreads to the arms. Blood pressure problems, heart rhythm problems, and breathing difficulty may occur in critical cases. However, despite the severity of the disease, recovery rates are good when patients receive treatment early.
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:
- Several rare inherited diseases
- 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.