Neuropathy: Early Detection Offers Hope
Researchers report that amputations in people with diabetes dropped 65 percent between 1996 and 2008. Why the big improvement? It's all about early detection and managing risk factors. Health care providers are getting better at finding and monitoring diabetic neuropathy, the nerve damage caused by high blood glucose levels. Neuropathy affects an estimated two-thirds of people with diabetes, can cause irreversible damage, and even lead to amputations. Diagnosis is critical so those affected can take steps to minimize pain and loss. Blood glucose control can help slow the progression of all types of neuropathy.
It's a mouthful, but distal symmetric polyneuropathy, frequently referred to as peripheral neuropathy, accounts for about 95 percent of diabetic nerve disease, according to Solomon Tesfaye, MD, FRCP, of the University of Sheffield in England. Peripheral neuropathy is damage to the nerves that send signals from the arms, legs, hands, and feet to the brain. The American Diabetes Association (ADA) recommends that people with diabetes be screened for peripheral neuropathy once a year, starting at diagnosis for people with type 2 and five years after diagnosis for those with type 1. "The reason you want to diagnose neuropathy," according to Aristidis Veves, MD, DSc, of Harvard Medical School, is that "you have to identify patients at risk for foot ulcerations." People with ulcers—sores that won't heal—need to receive education about taking care of their feet and preventing injury, he says.
|What to Expect at a Foot Exam|
Detection: At a screening, a health care provider asks about typical peripheral-neuropathy symptoms. "Burning pain, pins and needles, electric shock-type pains that last seconds" are common, says Tesfaye. One distinguishing feature of this type of neuropathy is that it's often symmetric, occurring on the right and left sides equally. Tesfaye says there may be causes other than diabetes for the sensations, such as arthritis, so health care providers must rule them out before making a diagnosis.
Not everyone with peripheral neuropathy gets a painful wake-up call. "The most important thing is that a lack of symptoms doesn't mean a lack of neuropathy," says Veves. Up to half of peripheral neuropathy is asymptomatic. A foot test is recommended to detect subtle losses of sensation, which can be "just as bad as painful neuropathy because it can lead to amputation," says Tesfaye. There are several noninvasive tests to assess sensation levels (see "What to Expect at a Foot Exam"). "If there is a sensory level below which a patient feels no sensation of pain, vibration, or cold, or if they cannot feel a monofilament on the big toe, then they are considered at risk for ulceration," says Tesfaye.
Treatment: While there is no cure for peripheral neuropathy, potential treatments are in development. Blood glucose control can slow it down, and medications can control symptoms. Treatments for neuropathic pain include capsaicin cream, the skin-numbing lidocaine patch, some anti-seizure medications, antidepressants, and, as a last resort, opioid painkillers.
|While promising and exciting, these nerve tests aren't yet proven and remain in the realm of research.
It's an invasive procedure, but a biopsy of foot skin can reveal neuropathy if a lower-than-normal number of nerve fibers is detected.
One experimental neuropathy-detection device senses nerve conduction, while another measures nerve responses to changes in temperature.
A study found that a visual examination of the shape and quantity of nerve fibers in the eye could predict the health of nerves in the feet.
Deeper inside the body, nerves manage everything from heart rate to digestion. Diabetes can also damage these nerves, leading to autonomic neuropathy. These neuropathies tend to affect a particular organ or system, so doctors have developed tests specific to each type of neuropathy.
Symptoms of autonomic neuropathy often send people to their doctor seeking treatment, but not so much with cardiovascular autonomic neuropathy. Heart nerve damage often goes undetected—and can be deadly. That's why the ADA recommends annual screening for cardiovascular autonomic neuropathy for people with diabetes, at diagnosis for people with type 2 and five years after for those with type 1. Heart neuropathy is associated with an increased risk of cardiovascular disease, making it particularly dangerous. The nerve damage can cause numbness in the heart. People with heart neuropathy "may not have pain if they have angina," says Veves. That pain is important, as it's a sign that a heart attack may be imminent. A heart attack itself may also go undetected.
Detection: A resting heart rate that is too high (greater than 100 beats per minute) can indicate cardiovascular neuropathy. The cardiac nerves regulate heartbeat, making the heart slow down when at rest or speed up if extra blood is needed. Another test involves measuring blood pressure as a person goes from sitting to standing. Normally, the blood pressure should remain roughly constant because when one stands, the heart should automatically pump harder to get blood up to the brain. In people with damaged heart nerves, this system is defective; the heart rate doesn't increase as needed, and there's a measurable drop in blood pressure. A person may experience this as dizziness or lightheadedness upon standing.
Treatment: Blood pressure–raising medications can combat dizziness that occurs on standing. Increasing salt and fluid intake may help, but ask your doctor before making these changes.
Neuropathies that affect the gastrointestinal tract can lead to gastroparesis, diarrhea, and/or constipation. Gastroparesis occurs when the nerves that normally trigger the stomach muscles to push partially digested food into the intestines don't function properly and stomach emptying is delayed. The result can be nausea, vomiting, or low blood glucose because insulin can hit the bloodstream before food from a meal gets digested.
Detection: A gastric-emptying test involves eating a meal with a trace of radioactive material. A special scanner detects how quickly or slowly the meal passes out of your stomach. An endoscopy—in which a scope is routed through the mouth into the stomach—can help rule out other conditions that may masquerade as gastroparesis.
Treatment: Changing your diet to one that's easier to digest may improve gastroparesis symptoms. For example, a dietitian may recommend eating smaller meals more frequently. Anti-nausea medications and those that stimulate the stomach are other options. A gastric-pacing device may be placed under the skin of the abdomen to stimulate digestion. For severe cases, a surgeon may alter the digestive tract to bypass the lower part of the stomach to improve stomach emptying.
Nerve damage to the bladder can make it more difficult to completely empty the bladder. The ADA recommends testing for bladder neuropathy in people who have recurrent urinary tract or kidney infections, incontinence, or an inability to drain the bladder.
Detection: When bladder neuropathy is suspected, a doctor may use ultrasound to measure how much urine remains in the bladder after urination, says Veves. Your doctor may order tests to rule out other causes of bladder problems, such as gynecological disorders or infections. (Erectile dysfunction can also be caused by neuropathy.)
Treatment: A doctor may prescribe a medication that helps the bladder contract and empty better. In addition, continuous antibiotic treatment can keep bacteria from getting out of control in people with chronic urinary tract infections.
Believe it or not, sweating is also controlled by nerves susceptible to damage by diabetes. Dry feet are a common neuropathy symptom, Veves says, and the condition can boost the risk for foot ulcerations. Excessive sweating can also develop as the result of damaged sweat gland nerves.
Detection: One way to diagnose this type of neuropathy is the quantitative sudomotor axon reflex test (QSART). It involves measuring the resting skin temperature, resting sweat secretion, and stimulated sweat secretion through a small cup placed on the skin. A computer analyzes the data to check the sweat response.
Treatment: If you sweat too much, a doctor may prescribe a medication that cuts down on perspiration.