Answers to reader questions about advances in treatment for peripheral neuropathy and tardive dyskinesia.
A. Gordon Smith, M.D., is professor and vice chair of neurology, chief of neuromuscular medicine and director of the Peripheral Neuropathy Study Group and Cutaneous Innervation Laboratory at the University of Utah. Dr. Smith is also a Fellow of the American Academy of Neurology.
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Your Questions Answered
Q What's on the horizon for restoring nerve function in peripheral neuropathy? Will there ever be a way to quiet the faulty nerves, as opposed to masking the pain with drugs like gabapentin and oxycodone?
DR. A. GORDON SMITH RESPONDS:
A It is estimated that more than 20 million Americans have peripheral neuropathy, making it one of the most common neurologic conditions. Peripheral neuropathy is caused by damage to the peripheral nervous system, which is responsible for sending information back and forth between the brain and spinal cord to every other part of the body. The condition often causes weakness, numbness, and pain in the hands and feet, but it may also occur in other areas of the body. Because peripheral neuropathy is not a single disease but rather a symptom with many possible causes, it may be difficult to diagnose and to treat.
However, different forms of peripheral neuropathy may also share common mechanisms of nerve injury. This means that discovery of a treatment for one form of peripheral neuropathy might benefit others.
Diabetes is the most frequent cause of peripheral neuropathy. In many cases, the cause of peripheral neuropathy is never known (called idiopathic peripheral neuropathy). Patients, physicians, and researchers are all interested in discovering effective therapies to slow progression, improve pain control, and hopefully reverse nerve injury in peripheral neuropathy.
Recent advances in uncovering the genetics of peripheral neuropathy have been made. Researchers have discovered that some people with painful idiopathic peripheral neuropathy have a mutation in a particular gene. This discovery has led to new studies—including planned human trials—exploring these genetic mutations as potential targets for treatment.
In addition, patients are being actively recruited for a number of exciting clinical trials including studies of growth factors (groups of proteins that stimulate the growth of specific tissues) delivered using gene therapy technology, which allows targeted delivery for peripheral neuropathy caused by diabetes. (Read more on these therapies at bit.ly/1eaBc0H.)
For many neuropathies caused by an immune attack of the nerves, good therapies already exist and others are in development. The outlook for these forms of peripheral neuropathy is even more hopeful. For patients with chronic inflammatory demyelinating polyradiculoneuropathy (a rare and chronic condition characterized by gradually increasing weakness of the legs and, to a lesser extent, the arms), the use of corticosteroids or intravenous immunoglobulin (IVIg)—alone or in combination with immunosuppressant drugs—is effective. However, better treatments are needed for patients who do not respond to currently available approaches.
There is even hope for patients with certain types of genetic neuropathies. Several promising experimental treatments are being studied for familial amyloid polyneuropathy, a rare genetic condition where impaired nerve function is caused by amyloid protein deposits in peripheral nerves.
While the lack of a recognized underlying cause for idiopathic peripheral neuropathy is frustrating, we have learned a great deal about this disorder over the past decade. A number of studies now link obesity and its related metabolic consequences (such as insulin resistance and elevated lipids in the blood) with peripheral neuropathy. In addition, several studies suggest that successful diet and exercise can improve nerve regeneration and improve symptoms including pain. This provides a non-drug treatment approach that would immediately benefit many people with peripheral neuropathy.
Despite all of this good news, more research is urgently needed. Relative to the number of patients who have neuropathy, very few research grants are funded. To help change this, consider joining one of the patient advocacy organizations focused on neuropathy. For example, the Neuropathy Association has many programs to encourage involvement and advocacy: www.neuropathy.org.