Most people with diabetes aren’t fully aware of the dangers of diabetic nerve damage, or neuropathy, which include impotence, heart-rhythm abnormalities, and amputations. Neuropathy affects 90% of people who have had either Type 1 or Type 2 diabetes for more than 10 years, although the symptoms can be subtle or even absent. Most commonly thought of as a foot-care issue, neuropathy actually has several forms and can affect many parts of the body. New tests make diagnosing neuropathy easier, yet long-available, simple tests are still effective and underused weapons.
Even though current knowledge of treating neuropathy lags behind knowledge of how to diagnose it, knowing you have neuropathy is valuable because it allows you to take steps to prevent more serious complications. This article describes two general forms of neuropathy, peripheral and autonomic, and some of the tests used to diagnose them.
Peripheral neuropathy, which affects the feet, legs, and, less commonly, the hands, is dangerous because its symptoms can be so subtle. In fact, the “symptomless” foot is most likely to have a problem.
“Pain is what takes most people to the doctor’s office,” says John B. Perry, DPM, a podiatrist in Portland, Maine, who specializes in diabetic foot care. “If it doesn’t hurt, you don’t come in. The problem is, people with diabetes don’t have the same sensations in their feet. You have to check and have them checked when they don’t hurt.
“I tell people with neuropathy that the nerves in their feet aren’t sending information anymore,” he says, “and that they have to use their brain and their eyes and their fingers to save their feet.”
The damage and the danger from diabetic peripheral neuropathy comes from two basic problems: loss of nerve function and loss of blood supply. Both are caused by the primary dysfunction of diabetes: too much glucose in the blood.
The damage that high blood glucose levels do to the nerves is a complex and still not fully understood cascade of cellular events that is often described as a “dying back” of the nerve fibers. The nerve fibers, the insulating layer that surrounds them, and the cell bodies that supply the nerve with food and fuel, die off. The damage begins at the ends of the longest nerves — those that go to the toes — first, but can eventually affect any and all parts of the peripheral nervous system.
Diabetes also reduces blood flow to the nerves and to the extremities. This contributes to neuropathy and injury, and also affects the body’s ability to heal injuries.
Foot disease caused by neuropathy is the most common complication leading to hospitalization of people with diabetes, but according to the National Institutes of Health, only half of people with diabetes check their feet daily. Each year, some 86,000 Americans with diabetes have a lower-extremity amputation, and up to 85% of those losses could have been prevented.
The first and most important step to protecting the feet is preventing injury, whether or not neuropathy has been diagnosed. The most common cause of injury to the feet is improperly fitting footwear. People who do not have neuropathy respond to repetitive stress or pain in their feet by shifting their weight or posture, adjusting their gait, or fixing their shoes. A person with neuropathy does not have the same sensations of pain or discomfort, so the stress goes unrelieved and progresses to a blister or sore, which can develop into an ulcer that requires medical attention. People with diabetes are particularly prone to foot problems as they age, so vigilance becomes ever more important.
“Even without diabetes,” Dr. Perry says, “the feet have wear and tear from aging. The toes contract and become less flexible, and where a flexible toe moves with shoe gear, a rigid toe rubs against it. Our arches flatten as we age, and the foot widens. Without diabetes, someone can feel the effects of these changes. With diabetes, they don’t feel them, and they’re at risk for a blister or a callus.