Diabetes is a risk factor for stroke, nerve damage, and cognitive impairment. While stroke is technically a cardiovascular complication caused by a blockage of blood to or a hemorrhage in the brain, it can cause impairment to memory, vision, speech, movement, and other brain functions in varying degrees of severity.
The other major neurological complications of diabetes are caused by neuropathy, or nerve damage. The exact way that diabetes causes nerve damage is not completely understood yet, but it's thought that over time high levels of blood glucose damage the nerve cells, which unlike other cells don't require an insulin “key” to allow glucose inside them. Researchers have also hypothesized that too much glucose causes depletion of nitric acid, which in turn cuts off blood supply to the nerves.
Peripheral Neuropathy (PN)
Peripheral neuropathy is often called stocking-glove syndrome because it most commonly affects the feet and hands. The condition can be particularly troublesome in the feet because of the chance that you may develop an injury that you don't notice, and compound the problem through the simple act of walking.
Symptoms of peripheral neuropathy include the following:
A feeling of “pins and needles”
Tingling and/or burning sensations
In some people, pain
Balance problems (if PN is present in the feet)
Reflex problems and muscle weakness
Neuropathies are either diffuse (affecting a wide area or several areas of the body) or focal (affecting a specific place on the body). Most neuropathic conditions related to diabetes are diffuse, including peripheral and autonomic neuropathy.
The antidepressant medications duloxetine (Cymbalta), amitriptyline, and desipramine may be useful in blocking pain signals, although side effects may be an issue for some patients. Gabapentin (Neurontin) and pregabalin (Lyrica), both anticonvulsant drugs, are also effective treatments for many people with PN and have the additional advantage of having few side effects. A number of studies have also shown promising treatment results with alpha lipoic acid (ALA) treatment, although ALA is not FDA-approved for this particular use at this point in time.
Topical (on the skin) treatment with lidocaine, evening primrose oil, or with capsaicin cream, which contains a substance derived from hot peppers that helps to block pain signals, may also be recommended by your doctor. And some anecdotal success has been reported in treating PN with acupuncture and with transcutaneous electronic nerve stimulations (TENS), a procedure that uses electrical waves to block pain signals.
If you have painful peripheral neuropathy and have difficulty sleeping because of it, you may want to invest in a bed cradle. A bed cradle is a device that elevates sheets, blankets, and other bedding above sensitive spots on feet and legs so you can sleep in comfort but still stay warm.
Anodyne therapy is another PN therapy using flexible pads containing a series of light-emitting diodes (LEDs) that use infrared light and energy to penetrate the skin. The light energy and heat is purported to improve circulation and reduce pain. Pads can be placed on the feet, hands, or elsewhere. Published research has conflicted on whether or not anodyne therapy has any lasting therapeutic value in the treatment of PN, and further studies are needed to make this determination.
While many people with diabetes are aware of the signs and symptoms of PN, significantly fewer are educated about, or tested for, autonomic neuropathy. A stealth disorder, autonomic neuropathy short-circuits the nerves that control the sympathetic (autonomic or involuntary) nervous system. Blood pressure, heart rate, perspiration, salivation, gastrointestinal and bladder function, sexual potency, and vision can all be impaired by autonomic neuropathy damage.
Autonomic neuropathy causes a wide spectrum of nonspecific symptoms ranging from constipation and diarrhea to dizziness and excessive perspiration (see the following table). Unfortunately, these are also common signs of a number of medical conditions, which makes autonomic neuropathy particularly difficult to detect without regular screening. Often, a diagnosis isn't made until organ damage has occurred.
Drop in blood pressure
No variation in heart rate
Elevated resting heart rate
Shortness of breath
Silent heart attack
Bloating and nausea
Premature feeling of fullness
Urinary tract infections
Inability to maintain erection
Decreased or increased urination
Nephropathy (kidney damage)
Increased perspiration (trunk and face)
Decreased perspiration (extremities)
Dry, thick skin on hands and feet
Skin rashes and infection
No pupil response to light/dark
Impaired night vision
Cardiovascular Autonomic Neuropathy (CAN)
This disorder begins silently without symptoms of chest pain or discomfort (angina), and often remains undetected until serious myocardial infarction (death of a portion of the heart muscle due to lack of oxygen) has occurred. As a result, these “silent heart attacks” often pass without proper medical attention.
If you experience any unexplained shortness of breath, weakness and fatigue, and/or excessive perspiration — all possible symptoms of silent heart attack — report these to your doctor. The mortality rate of CAN is up to 50 percent within five years once symptoms appear, so prevention and proper treatment is essential.
I get dizzy when I stand suddenly, and my doc said it could be neuropathy. Isn't that a foot condition?
Your doctor is talking about autonomic neuropathy. Cardiovascular autonomic neuropathy can trigger a sudden drop in blood pressure known as orthostatic (postural) hypotension. When you stand up, blood vessel and nerve damage prevent the blood pressure from rising quickly enough to compensate for the change in position, and dizziness, vision problems, and lightheadedness result.
Patients with CAN have little variation in their heart rate, which typically remains continuously elevated both at rest and under stress (e.g., after exercise). Heart rate variability (HRV) testing is used to diagnose the condition. HRV testing involves assessing the heart rate with an electrocardiograph (ECG) during activities of deep breathing, a postural test (i.e., lying down, rising, and standing), and a Valsalva maneuver.
A Valsalva maneuver is performed by bearing down or forcefully breathing out through the mouth with the nose closed. In patients without CAN, the heart rate should slow during this maneuver. If heart rate remains consistent (i.e., does not slow or speed up) during all three of these activities, CAN is suspected.
Autonomic neuropathy can also cause hypoglycemic unawareness, a potentially serious inability to detect the physical symptoms of a low blood glucose episode.
People with diabetes may experience memory problems and cognitive impairment, but it isn't completely clear whether these problems are a result of physical processes, the social and psychological toll of the disease, or a combination of the two.
There is some evidence that impaired glucose tolerance, a precursor to type 2 diabetes, can cause memory loss and atrophy of the hippocampus (the part of the brain responsible for learning and memory). Research has also indicated a greater risk for cognitive impairment in people with type 1 diabetes, possibly because of their increased risk for and incidence of hypoglycemia.
There are plenty of medical reasons for children and their parents to avoid hypoglycemia, of course, but researchers disagree on whether long-term cognitive dysfunction is one of them. Some studies have shown a connection between severe hypoglycemia and learning difficulties in children with type 1 diabetes, but others have contradicted this finding. Further research is necessary to determine the correlation between diabetes and cognitive impairment.