Also referred to as peripheral neuropathy or peripheral neuritis, neuropathy occurs when illness, injury, inflammation, medication, or other factors disrupt the ability of nerves outside the spinal cord to relay messages between the brain and muscles, skin, nerves, joints, or internal organs.
Neuropathy can affect:
- Sensory nerves, which control sensation
- Motor nerves, which control movement
- Autonomic nerves, which control involuntary or semi- involuntary body functions
- Any combination of these three main types of nerves
Researchers have identified more than 100 types of neuropathy. Symptoms, which may take days, weeks, or months to develop, depend on the type or types of nerves affected and on whether neuropathy affects a single nerve or group of nerves (mononeuropathy) or more than one nerve group (polyneuropathy).
Damage to sensory nerves can reduce or intensify sensation. This can prevent patients from realizing they've been injured or are experiencing pains warning of heart attack or other life-threatening emergency. Or, it can make even a gentle touch extremely painful. Nerves farthest from the brain and spinal cord are usually the first to malfunction. Pain and other symptoms often appear on both sides of the body, beginning in the feet and progressing toward the center of the body. Neuropathy that affects sensory nerves also causes nerve pain, burning, tingling, and numbness. Inability to determine joint position impairs coordination.
Cramping may indicate motor nerve damage, which reduces or destroys muscle control and can result in weakness and loss of muscle. Other symptoms of muscle involvement include:
- Breathing or swallowing problems
- Absence of fine motor skills needed for such tasks as tying shoes
When autonomic nerves are damaged, diminished ability to sweat or otherwise regulate body temperature can cause heat intolerance. Vision may blur, and falling blood pressure can cause fainting or dizziness. Other symptoms include:
- Abdominal bloating
- Feeling full after eating very little
- Nausea or vomiting after meals
- Unintentional weight loss
- Urinary hesitancy or incontinence
- A sense that the bladder doesn't fully empty
Symptoms of acute neuropathies begin suddenly and worsen rapidly. Damaged nerves heal slowly. Initial symptoms of chronic neuropathies are subtle. These conditions progress slowly and may remain unchanged for months or years. Symptoms may abate before they recur. Chronic neuropathies may worsen over time, but are rarely fatal.
Injury is the most common cause of nerve damage. Broken or dislocated bones can press on nearby nerves. Slipped disks can pinch nerves emerging from the spinal cord. More severe trauma can crush, compress, stretch, or sever nerves. Causes include vitamin deficiencies, excessive alcohol use, medication, and exposure to toxic compounds or very cold temperatures. Some people inherit a tendency to develop neuropathy. This condition can also be a complication of systemic or metabolic disorders such as cancer or uremia and of infectious or inflammatory conditions such as HIV/AIDS, hepatitis, Lyme disease, lupus, or rheumatoid arthritis. High blood glucose levels characteristic of diabetes are a main cause of neuropathy. About 60-70% of people who have diabetes have mild to severe nervous system damage.
"Neuropathy poses a risk to a diabetic patient," notes Luigi Meneghi, MD, director of the Diabetes Research Institute's Kosow Diabetes Treatment Center at the University of Miami. "Loss of sensation might cause injury or infection to go undiscovered until the problem is well advanced. It's important to detect significant loss of protective sensation and, when detected, to make sure the patient understands how to care for the feet to prevent problems."
Anyone at risk for neuropathy should moderate alcohol use, eat a balanced diet, and pay close attention to any other health issues.
People who have neuropathy have so many diverse symptoms that the condition is difficult to diagnose. A complete neurological examination includes a detailed history that encompasses the patient's:
- Social habits
- Exposure to mercury, industrial chemicals, or other toxins
- Risk for infectious disease
- Family history of neurologic disease
The patient's history and symptoms and their suspected cause determine which diagnostic tests should be performed. Blood tests can detect diabetes, vitamin deficiencies, liver or kidney dysfunction, and other metabolic or immune system abnormalities that may be the source of symptoms. Cerebrospinal fluid may contain neuropathy-related abnormalities, and neurologic tests can reveal abnormalities in movement, sensation, and organ function.
Electromyography (EMG) involves inserting a needle electrode through skin and into muscle. The electrical activity detected when the patient flexes the muscle indicates how the muscle responds to nerve stimulation. Results are displayed on a fluorescent screen.
A patient who has an EMG will probably also have nerve conduction velocity testing. This procedure measures nerve damage by the speed at which an impulse travels along a nerve. Surface electrodes placed on the skin above the nerve emit mild electrical stimulation. Other electrodes record the resulting activity.
Nerve biopsy involves removing a small amount of tissue from the lower leg or elsewhere for laboratory examination. This invasive procedure can yield important information about the extent of nerve damage. Nerve biopsy is difficult to perform. It may cause neuropathic side effects, and many physicians believe neuropathy can be diagnosed without it.
Easier to perform that nerve biopsy, skin biopsy has fewer side effects than the more invasive procedure. Skin biopsy removes a thin section of skin, which is examined for damage to small nerve fibers.
Inherited neuropathy can't be cured, but patients can be made more comfortable. If your loved one is bedridden or will be in the same position for a long period of time, padding vulnerable parts of the body can reduce the risk of nerve damage. Active and passive exercise can relieve cramps and preserve and strengthen muscles.
Treating injuries promptly lessens the likelihood of nerve damage. Smoking cessation is especially important, because smoking can intensify symptoms by narrowing blood vessels that nourish peripheral nerves.
Controlling blood glucose levels may reduce neuropathic symptoms and prevent additional nerve damage in people who have diabetic neuropathy. Symptoms resulting from inflammatory or autoimmune conditions can be treated with immunosuppressive drugs or plasmapheresis, in which blood is removed from the body, cleansed of immune system cells and antibodies, then returned to the body.
Over-the-counter pain relievers may relieve mild symptoms. Severe chronic pain is treated with a variety of prescription medications. Surgery can provide temporary relief of severe chronic pain, but the operation itself can cause complications.