Nearly 24 million Americans deal with the challenges of diabetes every day, according to the latest statistics from the Centers for Disease Control and Prevention. A percentage of people with type 1 or type 2 diabetes also face a challenge called diabetic autonomic neuropathy and never know it until the complication becomes severe.
Diabetic autonomic neuropathy is a sub-group of diabetic neuropathy, a group of nerve diseases affecting the peripheral nerves outside the brain and spinal cord. There are three kinds of peripheral nerves: motor, sensory, and autonomic. Motor nerves carry signals to different muscle groups. Sensory nerves return those messages back to the brain--they work largely on a conscious level. Autonomic nerves control digestion, bowel, and bladder function, sexual response, perspiration, heart rate, and blood pressure, and the ability to know when blood sugar is too low.
Unawareness of hypoglycemia (low blood sugar)
Normally, when blood sugar is too low (below 70 mg/dl), a person experiences shakiness. In a person with autonomic neuropathy, however, there may be no shakiness or other symptoms, making diagnosis difficult. Having low blood sugar and no symptoms does not always indicate autonomic neuropathy; other conditions can cause this as well.
Heart rate and blood pressure are affected because autonomic neuropathy can damage the nerves of the cardiovascular system. Blood pressure may drop sharply after a person sits or stands, causing a feeling of lightheadedness. Heart rate may remain high or too low instead of fluctuating with body functions and exercise.
Damage to the nerves of the digestive system can cause constipation (sometimes alternating with diarrhea), difficulty swallowing, and gastroparesis, a condition in which the stomach empties too slowly, causing nausea, vomiting, bloating, and loss of appetite. This condition can cause blood sugar levels to fluctuate greatly.
Urinary and sexual
A person with autonomic neuropathy can have problems with urination and sexual function. Nerve damage can prevent the bladder from emptying completely, which can lead to bladder infections. Urinary incontinence also may develop because a person may not be able to sense when the bladder is full. A man with this condition may have problems having an erection due to damage to nerves that cause an erection; a separate problem, damage to the penis, may be also cause problems having an erections. A woman may have problems with vaginal dryness, arousal, or orgasm.
Damage to the nerves that control sweating means that the person has trouble regulating body temperature; night sweats or sweating while eating also may occur.
Autonomic neuropathy also can affect the pupils of the eyes, causing the eyes to adapt slowly to changing light. This makes it difficult to see when driving at night or when a light is switched on in a dark room.
A difficult diagnosis
Diagnosis of diabetic autonomic neuropathy is not easy because the condition can affect so many organs.
With such general signals, it is not uncommon for symptoms of diabetic autonomic neuropathy to be misdiagnosed as other medical conditions, especially in the early stages.
How likely is it that a person with diabetes might have diabetic autonomic neuropathy? It usually occurs after a person has had diabetes 20 years or longer, or has had poor control of blood sugar. People with type 2 diabetes may have had high blood sugar levels for years before they are diagnosed so autonomic neuropathy, and other complications, may be diagnosed at the time diabetes is diagnosed.
Tests and treatments
While researchers do not yet know the exact causes of diabetic neuropathy, there are tests available to aid in diagnosis. Heart rate variability testing is one. It is a noninvasive procedure that measures heart rates under various conditions. The test takes 15 minutes. Irregular results point strongly to the presence of diabetic autonomic neuropathy. Checking the change in your blood pressure when you go from lying down to a standing position can help determine if autonomic neuropathy affects your blood pressure.