Diabetic Nerve Damage

There are three broad types of neuropathy: sensory, autonomic and motor:

• Sensory neuropathy (or peripheral neuropathy, usually just called neuropathy) affects the nerves that carry information to the brain about sensations from various parts of the body. For example, how hot or cold something is, what the texture of something feels like, the pain caused by a sharp object or heat, etc. This is the most common form of diabetic neuropathy. 
• Autonomic neuropathy affects the nerves that control involuntary activities of the body, such as the action of the stomach, intestine, bladder and even the heart. 
• Motor neuropathy affects the nerves that carry signals to muscles to allow motions like walking and moving fingers. This form of neuropathy is very rare in diabetes.

Sensory neuropathy can lead to pain, numbness or tingling in the extremities and, ultimately, an inability to feel heat, cold, pain or any other sensation in affected areas. Autonomic neuropathy can lead to impotence in men, bladder neuropathy (which means the bladder is unable to empty completely), diabetic diarrhea, or bloated stomach. Motor neuropathy can lead to muscle weakness.

If you are diagnosed with neuropathy, your physician may use terms to describe the type that you have based on whether only one side of your body is affected (asymmetric) or both sides (symmetric). If only one kind of nerve is affected, your doctor may say you have mononeuropathy. If several nerves are affected, the term polyneuropathy may be used.

Other terms may be used based on what parts of the body are affected, including:

• Distal neuropathy is a form of sensory neuropathy that affects the hands or feet. It can be asymmetric but is usually symmetric, and is the most frequently diagnosed type of neuropathy.
• Femoral neuropathy is painful sensory neuropathy that centers in the thigh muscles. It can be asymmetric or symmetric. 
• Diabetic amyotrophy is motor neuropathy that affects the thigh nerves, with resulting weakness often in addition to or instead of pain. It can be symmetric or asymmetric. 
• Gastroparesis is autonomic neuropathy that affects the stomach, preventing it from emptying normally. It can result in ulcer-like symptoms, vomiting, bloating, and poor absorption of food resulting in malnutrition and hypoglycemic episodes as food fails to be absorbed at the anticipated rate. High blood glucose can later result when the meal finally makes its way through the system. 
• Diabetic diarrhea is autonomic neuropathy that results in an erratic functioning of the small intestine. This can cause unformed stools to be passed. If the nerves which communicate with the sphincter muscles (which control passing a bowel movement) are not working properly, stool can pass without warning, and/or without the patient being able to control when it comes out, resulting in fecal incontinence. Constipation also can result when the large intestine is involved and the stool remains in the large intestine too long. 
• Bladder neuropathy occurs when the bladder nerves no longer respond normally to pressure as the bladder fills with urine, and do not enable the bladder to empty completely. Some urine continually stays in the bladder, leading to urinary tract infections. Symptoms of this problem include cloudy urine, painful urination, low back pain and fever. 
• Postural hypotension is autonomic neuropathy that results in low blood pressure when standing. In people with postural hypotension, the pulse does not go up to compensate for the change in blood pressure, so fainting and dizziness can result. 
• Charcot joint is also called neuropathic arthropathy and occurs when the bones in the feet fracture or "powder" and the foot becomes misaligned. The foot becomes deformed as a result of the lack of nerve stimulation, which causes the muscles to lose the ability to support the foot properly. Walking makes it worse. People who already have neuropathy in their feet and have lost sensation are at a greater risk of developing this. 
• Unilateral foot drop occurs when the foot can't be picked up because a nerve in the leg has been damaged either by blood vessel disease or compression. 
• Impotence is caused by autonomic neuropathy and/or sensory neuropathy, and/or blood vessel disease that leads to an inability to have and maintain an erection in men.

Peripheral neuropathy (more commonly called neuropathy) is a general term for diseases that cause damage to the nerves outside of the brain and spinal cord. While diabetes is a frequent cause of neuropathy, it is not the only cause. Nutritional deficiencies (B-12 and folate), chemical exposures, pressure on nerves, or medications (such as some of those used for chemotherapy or to treat AIDS) can also cause neuropathy.

Theories abound as to why exactly neuropathy occurs in people with diabetes. In general, diabetic neuropathy is thought to be a result of chronic nerve damage caused by high blood glucose.

Another theory is that certain intracellular metabolites, such as myoinositol, become depleted, leading to nerve damage. Still other theories hold that pathways such as the protein kinase C pathway, being studied by George King, MD, Director of Research and Head of the Section on Vascular Cell Biology and his colleagues at Joslin, are triggered by chronic high blood glucose, resulting in several diabetes complications, which might include neuropathy.

"Recent studies have suggested that decreased blood flow to the nerves can also contribute to the development of diabetic nerve disease," says Dr. King. There are multiple studies ongoing which are designed to improve blood flow to the nerves in diabetic animals and in patients. Two new categories of drugs being examined are called antioxidants and PKC inhibitors. Preliminary studies using these drugs have shown encouraging results in animal models of diabetes. Clinical trials are being planned and some are already in progress.

People may seek their healthcare provider’s help for treatment of pain, not knowing exactly what causes it. Men may come to the doctor concerned about a decreasing ability to have and maintain an erection. Increasingly frequent urinary tract infections may be another clue, as may be recurring diarrhea or constipation, or vomiting or symptoms resembling an ulcer. Fainting spells upon standing may indicate postural hypotension.

A physician may detect early signs of neuropathy. He or she may notice that knee and ankle jerk reflex tests show nerves aren't as responsive as normal, or may observe a dip in blood pressure when you go from a reclining to sitting position. These are signs that increased attention to blood glucose are warranted to try to limit further problems.

If you already have nerve damage, there are things that can be done to slow the rate of progression or treat the symptoms. Maintaining good glucose control, as well as healthy blood pressure and cholesterol levels, has been shown to prevent the progression of neuropathy. If you have numbness, you need to be vigilant about examining your feet for any unusual scratches or wounds. A foot self-exam every day will help you avoid further complications.

Neuropathy is not reversible, however, its symptoms are manageable. It is absolutely crucial for people with diabetic neuropathy to discuss the options for treatment with their healthcare professional before trying any treatment. Your doctor will be able to help you find the solution that works for you.

Some of the treatment options include:

• Antidepressants. It may sound unusual, but researchers have discovered that antidepressants can be very helpful in decreasing the pain of neuropathy. If your doctor prescribes it for you, it does not mean that he or she thinks you’re depressed. The medication works by blocking pain receptors, and usually takes about a month to be effective. There are a number of different antidepressants that can be helpful in the treatment of painful neuropathy, and some have been specifically approved by the Food and Drug Administration to treat neuropathy.
• Neurontin (gabapentin capsules).This is one of the most commonly used and effective medications to help with pain caused by neuropathy. Neurontin has relatively few side effects, so some people with diabetes may find this medication very helpful.
• Capsaicin. This is a topical cream applied to areas affected by neuropathy. Since it is a derivative of pepper, it is important that people with diabetic neuropathy find out if they are allergic to the cream before using a significant quantity. Be sure to do a small patch test first.
• Holistic or alternative treatments. Some people with diabetic neuropathy have found success with other forms of pain management such as biofeedback, meditation, hypnosis, or acupuncture.

The medications outlined above could be helpful in ending the discomfort of neuropathy, but prevention continues to be the number one way of avoiding the discomfort associated with this condition. By keeping tight control over your blood glucose, you may be able to reduce the symptoms associated with neuropathy, or avoid them altogether. By keeping your A1C at 7% or less, you’ll be taking control of your blood glucose, and increasing your chances of avoiding neuropathy.