Less well known, and perhaps more dangerous even than peripheral neuropathy, is autonomic neuropathy. This condition affects the autonomic nerves, the nerves that regulate involuntary body functions and systems such as the digestive system, the sexual organs, the urinary tract, the heart, and the sweat glands. Symptoms come in a wide variety of forms, including sexual dysfunction, delayed emptying of the stomach, diarrhea, and difficulty urinating.
Cardiac autonomic neuropathy, an important factor for cardiovascular mortality in people with diabetes, may cause “silent” heart attacks because people with this form of neuropathy don’t feel cardiac pain. Moreover, neuropathy may affect the ability of the heart to vary its rate in response to exercise or a change in position. This loss of heart-rate variability is predictive of serious cardiac problems.
“I believe that measurement of heart-rate variability will become a standard of care in due course,” says Dr. Vinik. “It was very difficult to do in the early days, but now there are several machines available that can do it in the doctor’s office in 10 or 15 minutes. You get a standardized report that gives you a number, and I believe that this number will be known as commonly as those for cholesterol, blood glucose, or hemoglobin A1c.
“In our practice,” he says, “every person with autonomic neuropathy gets a heart-rate variability test, as does every person who has had diabetes more than five years. Every person with Type 2 diabetes gets the test on the first day we see them because they may have had diabetes for seven or eight years already. There are a number of treatment options for improving heart-rate variability.”
Another form of autonomic neuropathy and a debilitating late-onset complication of diabetes is gastroparesis, a paralysis or dysfunction of the stomach that causes food to move through the digestive tract either too slowly or not at all. Serious cases are readily diagnosed, but more commonly, gastroparesis (or gastropathy) is subtle, causes unpleasant symptoms, and interferes with blood sugar control because food absorption is delayed.
At one time, the only way to diagnosis gastroparesis was with a complicated procedure that examined the different phases of contraction of the stomach and could only be done in a research laboratory. Then researchers developed the electrogastrogram, which is similar to an electrocardiogram. They found that the stomach could be subject to rhythm disturbances much like those of the heart: tachygastria (fast contractions), bradygastria (slow contractions), or gastric arrhythmia (irregular contractions).
“Unfortunately, there is no specific therapy for stomach arrythmias as yet,” Dr. Vinik says, “but we’re hopeful that they will be developed.”
Measurement and diagnosis of both peripheral neuropathy and autonomic neuropathy continues to advance. Right now, as always, the vigilance of the individual who has diabetes and the rest of the health-care team is the best prevention. Click here for a list of foot-care tips that can help you get started.