Comedian George Lopez was born with a genetic condition that causes kidney disease. In the years before he had a transplant in 2005, Lopez likely experienced uremic neuropathy—a painful neurologic complication of chronic kidney disease.
Neuropathy, which involves a degeneration of nerves, can cause numbness, prickling, a burning sensation, stabbing pain, or even electric shocks of pain, says P. James B. Dyck, MD, FAAN, professor of neurology at the Mayo Clinic in Rochester, MN. It can be triggered by kidney disease as well as diabetes, chemotherapy, physical injury, or repetitive motion injury such as carpal tunnel syndrome. Other risk factors, especially for people with diabetes, can include obesity, hypertension, high cholesterol, and smoking, says Eva L. Feldman, MD, PhD, FAAN, endowed professor of neurology at the University of Michigan in Ann Arbor.
Regardless of the cause, untreated neuropathy poses serious health threats. “We worry most about pain and poor balance leading to falls,” says A. Gordon Smith, MD, FAAN, chair of neurology at Virginia Commonwealth University in Richmond. “Among patients with diabetes and certain forms of inherited neuropathies, we also worry about foot ulcers.”
There are several kinds of neuropathies—in addition to uremic neuropathy—each of which has different possible causes and treatments.
Peripheral Neuropathy
This type of neuropathy affects the peripheral nerves—the ones that involve the arms and legs. Causes may include a buildup of nerve-damaging toxins (as in uremic neuropathy, associated with chronic kidney disease) or elevated blood sugar associated with diabetes. Symptoms most commonly include numbness, tingling, prickling, or weakness in the arms and legs. Usually the disease involves the ends of nerves, so the feet and hands are most affected. The condition can cause burning pain or disrupt signals between the arms and legs and the brain, interfering with balance and gait and increasing the risk of falls and injury. “Peripheral neuropathy is not a single disease,” says Dr. Dyck. To treat it, physicians address underlying causes. With uremia, for example, the toxins are filtered through dialysis or a kidney transplant. If the cause is elevated blood glucose, patients may be prescribed medication and encouraged to exercise, improve their diets, and quit smoking.
Diabetic Neuropathy
As the name suggests, this condition is caused by type 1 or type 2 diabetes. It affects the longest nerves, causing numbness, tingling, or pain in the feet. A lack of sensation in the feet may lead to ulcers on the toes and feet that if left untreated can become infected and require amputation. Diabetes also can damage the autonomic nerves, which control blood pressure and gastrointestinal, bladder, and sexual function. Treatment focuses on prevention: Exercise, a healthy diet, and medication are recommended to keep blood sugar levels under control and manage high blood pressure and cholesterol, says Dr. Smith. “Patients are encouraged to check their feet every day to look for calluses or injuries that could develop into ulcers,” he says. To relieve pain, physicians may prescribe tricyclic antidepressants such as amitriptyline and nortriptyline, anticonvulsants such as pregabalin (Lyrica) or gabapentin (Neurontin), or serotonin norepinephrine reuptake inhibitors such as duloxetine (Cymbalta).
Hereditary Neuropathy
There are many forms of inherited neuropathies that can affect motor, sensory, and autonomic nerves. The most common is Charcot-Marie-Tooth disease, which involves the motor and sensory nerves, resulting in weakness and numbness of the feet and sometimes the hands. Hereditary sensory and autonomic neuropathies (which are rare) can cause numbness, pain, foot ulcers, and autonomic problems such as abnormal sweating and poor blood pressure control. Doctors use genetic and nerve testing to diagnose the condition. They prescribe physical therapy and pain medication to treat symptoms. Gene therapies also show promise in treating some hereditary neuropathies, says Dr. Smith. “We now have effective gene-based treatments for a specific form of hereditary neuropathy called hereditary transthyretin amyloidosis.”
Small Fiber Neuropathy
In this type of neuropathy, the small sensory nerves and autonomic fibers are affected. Symptoms include numbness, burning, and pain, often starting in the feet, says Dr. Dyck. Although it can be caused by diabetes, small fiber neuropathy also has been linked to thyroid disease, chemotherapy (due to the toxins introduced into the body), dysfunction of connective tissues, and other causes. It can affect the digestive system, cause fatigue, and trigger chronic pain. Consequently, it is sometimes misdiagnosed as fibromyalgia. For this reason, researchers are exploring effective screening options such as sensory testing and a skin biopsy using a sample taken from the lower leg in which the nerve fibers in the skin are counted. “Before we consider the best treatment,” says Dr. Dyck, “we must first identify the underlying disease.”
Neuropathy and COVID-19
Having neuropathy does not appear to increase the risk of contracting COVID-19, says Anne Louise Oaklander, MD, PhD, FAAN, associate professor of neurology at Harvard Medical School. “But patients who use corticosteroids or other immunosuppressants have a higher risk of all types of infections, so they should discuss dosages with their doctors—and get vaccinated.” They also should be strict about social distancing, wearing masks, and monitoring symptoms.
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