Peripheral neuropathy: Advice from a Mayo Clinic specialist
Peripheral neuropathy: Advice from a Mayo Clinic specialist
Peripheral neuropathy. A Mayo Clinic specialist provides tips for managing this often painful disorder.
David Martin, M.D.
Some people with peripheral neuropathy don't even notice it. Others are debilitated by pain and numbness. What's going on inside the body to cause such widely varying symptoms? How can something that's numb also hurt?
David Martin, M.D., who specializes in pain medicine at Mayo Clinic, Rochester, Minn., explains the phenomenon and offers some suggestions for living with peripheral neuropathy.
What is peripheral neuropathy?
Peripheral neuropathy means that nerves in the extremities are damaged. The most benign effect of nerve damage is nerve irritability, which makes the damaged nerve send signals when it shouldn't. This sensation may simply be annoying, such as mild tingling or itching, but it can become very unpleasant or painful. In those cases, people usually describe the sensation as burning, electric shock-like, or pins and needles.
These unpleasant sensations can occur in response to touch, temperature, or even with no stimulus of any kind. Sometimes, even the lightest touch is painful because the response is inappropriately amplified. As nerve damage progresses, numbness results. All these sensations can occur at the same time.
It's puzzling because you can't see the injured nerve or anything wrong with your hand or foot, but it hurts. It can feel numb and hurt at the same time, and that seems contradictory. Some people don't tell their doctor because they think their symptoms don't make sense. But these sensations are real. Your doctor can do the necessary tests to determine the cause, and there are literally hundreds of causes.
What causes peripheral neuropathy?
Neuropathy may be caused by a variety of diseases or disorders. For example, a problem in nerves in the foot could be caused by diabetes. Other causes include vitamin deficiencies, hereditary disorders, inflammatory conditions, and exposure to toxic substances (including some medications) or alcohol. Diabetes is the most common cause.
Each cause may damage the nerve in a different way, but the symptoms are similar. The nerve doesn't function properly. It's like when your car doesn't start. It doesn't matter if it's a dead battery or a bad fuel pump. It just won't start.
How is peripheral neuropathy diagnosed?
Your doctor should ask about diseases you have, and those that run in your family. He or she will also need to know about all medications you take, including nonprescription and dietary supplements. A neurological examination and blood tests follow the interview. Sometimes additional testing, including magnetic resonance imaging (MRI), electrical nerve testing, spinal tap or a nerve biopsy, is required.
You can have peripheral neuropathy and not be aware of it. Your brain filters out a lot of sensations every day. For example, unless you think about it, you're not aware of the sensation of your clothing on your body. If your brain didn't filter out this sort of thing, you'd be overwhelmed.
This means you could have diabetic neuropathy and not realize it until another problem occurred. For example, you might take a chemotherapy medication at a dose low enough that it shouldn't cause any problems. But you might develop a major problem when both things are happening together.
Why does it target fingers and toes?
The longer the nerve, the more vulnerable it is to injury. Peripheral neuropathy usually affects the nerves at their furthest reaches from the body, and the nerves going to the toe can be more than 3 feet long. Single nerve cell fibers reach all the way from the big toe to the spinal cord. They're some of the longest — if not the longest — nerve cells in the body.
Why doesn't the nerve hurt all along its length?
In very simple terms, it's as if nerves for the toe are wired to the "toe" area of your brain. No matter where the nerve is damaged along its length, when it fires you feel pain in your toe. Because the longest nerves in your body often are affected first, the symptoms may begin in the toes and then move up to the feet, and then to the legs.
How is peripheral neuropathy treated?
First, any underlying conditions are treated. That's why it's so important to try to determine the cause of the problem. If it's due to a chemotherapy drug, perhaps the dose can be reduced. In diabetes, the nerve damage seems to be related to high blood sugar, so better control of diabetes can improve damage to the nerves.
The next step is to try to control painful symptoms with a medication. There are several classes of medications that can help:
How does an epilepsy drug reduce pain?
There are several possible mechanisms, but primarily these medications calm irritable nerves, whether they're in your brain causing seizures or in your feet causing burning pain. The most common anti-seizure drug prescribed for nerve pain is gabapentin (Neurontin). In fact, gabapentin is probably prescribed more often for pain than for epilepsy.
Similarly, antidepressants affect not just mood, but also perception of pain. Some people may resist taking an antidepressant because they think that means the doctor believes their pain is all in their heads. But that's not it at all. Some antidepressants also reduce pain.
What types of antidepressants work best for pain?
Tricyclic antidepressants are good for pain but frequently cause side effects. Selective serotonin reuptake inhibitors (SSRIs) have fewer side effects but work less well for pain. Newer antidepressants called serotonin and norepinephrine reuptake inhibitors (SNRIs) are somewhere in between. SNRIs work well for pain and cause few side effects.
Is it difficult to find a drug that works?
It can be. Even in the same family of medications, one drug will work for you while another one won't. Your response to a drug depends on your condition and unique genetic profile. It's important to carefully weigh the good effects of a medication against its side effects, and make sure the balance is in your favor.
What nondrug therapies do you recommend?
If you're having a lot of pain in your hands and feet, you probably are avoiding touching them. But massage can help desensitize those areas. Another desensitization technique is to soak your hands and feet, alternating between cold and warm water.
There is no treatment for the loss of sensation and strength. If your hands and feet are numb, you may have trouble walking or doing other physical tasks. But to maintain the muscles that move your hands and feet, you must use and stretch them. Supportive devices, such as splints and braces, may compensate for loss of strength and improve function. A physical therapist or occupational therapist often can help you find new ways to do activities more efficiently and prevent injuries.
For example, people whose hands are affected may get burned while cooking before they know that they've touched something hot. If their feet are numb, they may not notice a stone in their shoe, or may stumble over a throw rug. You need to be proactive. Get serious about fall prevention before you've broken your hip.
What else should people do?
If your feet are numb, you should inspect them daily for any sores or cuts. This is especially important for people with diabetes, which slows the healing of damaged tissue. If you routinely get up every night to go to the bathroom, make sure you have night lights and that the pathway is clear. Get rid of throw rugs or extension cords that might trip you.
With numbness, you need to be careful about damage from heat or frostbite. You need to use your brain because your body can't remind you.
Does peripheral neuropathy ever get better?
Many neuropathies do get better over time. They can heal themselves if the underlying cause is removed. It takes time and doesn't always happen, but you should never give up hope.
In many cases, your body just adapts to the problem. Neuropathy can stop being painful after a while, or your brain can adapt, so you'll have less difficulty using your hands and feet.
Last Updated: 05/24/2006
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