When your senses are off-balance
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: Several years ago, my father developed numbness in the soles of his feet, which gradually migrated from his toes to his ankles. Now, his feet hurt, and he's having trouble with balance. His doctor diagnosed him with idiopathic peripheral neuropathy. We would appreciate any information you could give us about this problem.

A: The nervous system has two parts: The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of the nerves that fan out to the rest of the body. The peripheral motor nerves carry commands from the central nervous system to all parts of the body, and the peripheral sensory nerves carry messages about pain, pressure, temperature and balance back to the spinal cord and brain. Peripheral neuropathy occurs when nerves in the peripheral system are damaged or weakened. In your father's case, the sensory nerves are abnormal.

Many things can cause peripheral neuropathy. Diabetes is the most common culprit. In some cases, neuropathy develops before diabetes becomes evident, so your father should be retested for diabetes periodically. Recent research suggests that careful control of blood-sugar levels may stabilize nerve function. So if your father eventually turns out to have diabetes, diet or medication to control his sugar may help. Other causes include alcoholism, dietary deficiencies (especially a lack of B vitamins), physical trauma, blood-vessel problems and immune system disorders like rheumatoid arthritis or lupus. But at least a third of all cases are idiopathic, meaning they have no known cause.

The symptoms of peripheral neuropathy can vary quite a bit. The condition can cause a burning, shooting pain through the feet or hands. Other symptoms include tingling or numbness in the feet or hands, or even tickling or other abnormal sensations. Muscle weakness can also occur.

The real danger of peripheral neuropathy is that it makes people less sensitive to heat, cold, pressure and pain, especially in the feet. As a result, poorly fitting shoes, high-impact exercise and even walking raises the risk of a foot injury. Peripheral neuropathy can also make daily activities (such as driving a car) challenging.

People who have this condition should pay extra attention to their feet. Your father should examine his feet at least once a day to be sure that he hasn't developed a sore or lesion. Since his nerves may no longer communicate pain efficiently, he will need to rely on his eyes to detect any problems.

As for treatments, some people find it helpful to wear loose-fitting, softsoled shoes and thick socks. Others are very sensitive to heat. They may find some relief by wearing open-toed shoes or by soaking their feet in ankle-deep cool (but not cold) tap water for 15 minutes at bedtime. In any case, it's important for all neuropathy sufferers to wear well-fitted shoes, avoid going barefoot and protect their feet from trauma.

Medications may also be helpful. Your father should talk to his doctor about drugs such as gabapentin (Neurontin), amitriptylline (Elavil and others), and carbamazepine (Tegretol and others). Doctors have also used newer antidepressants, such as paroxetine (Paxil) and citalopram (Celexa) for people with this condition. Complete relief is uncommon, but with neuropathic pain, even a partial benefit is welcome.

For hard-to-treat conditions like peripheral neuropathy, doctors often have to try a series of different medications until they find something that works. If all else fails, your father might ask his physician about trying a combination of medications. But be aware that these combinations usually haven't been studied well in research trials. Another option is to raise the dose of medication if a patient's pain is especially bad. Given a choice between pain and side effects from high doses of medication, many people will accept some side effects as the price to pay for relief.

Most people have never heard of peripheral neuropathy, but patients who struggle with the condition know it all too well. It can be hard to treat, but many patients benefit from a combination of simple precautions and medication for pain. Scientists are working hard to learn more about nerve ailments. They hope to develop new and better methods of diagnosis and treatment to help your dad and others like him.

Copyright 2007 the President and Fellows of Harvard C o l l e g e . Developed by Harvard Health Publications (www.health.harvard.edu) . Distributed by UFS. Submit questions to harvard_ adviser@hms.harvar