Diabetic Neuropathy
Questions and Answers

Question: What is a diabetic neuropathy?
Answer: Diabetic neuropathy is a nerve damage caused by diabetes mellitus.

Question: How common is diabetic neuropathy?
Answer: Sixty percent of diabetics develop one form or another of neuropathy within 10 years of the diagnosis of their diabetes. Only half of them have symptoms from such neuropathy.

Question: What causes diabetic neuropathy?
Answer: The exact cause of diabetic neuropathy is not clear. There are several theories, such as:

• Tissue glycosylation: High blood sugar can cause chemical changes in the nerves, impairing their ability to transmit signals.
• Genetic factors: Some patients are more susceptible for nerve damage secondary to diabetes than others, due to their genetic constitution.
• Sorbitol formation: Impairment of glucose utilization can activate alternative pathways for glucose metabolism. One of these pathways reduces glucose to a sugar called sorbitol, which causes swelling and damage of the nerve cells, leading to diabetic neuropathy.
• Low nitric oxide activity: Diabetics have low nitric oxide activity. Nitric oxide normally causes dilatation of blood vessels. Lack of nitric oxide causes constriction of blood vessels leading to ischemia of the nerves.
   

Question: Can diabetic neuropathy be prevented?
Answer: The answer is yes. A recent study called diabetic complication and control trial (DCCT) has studied about 1,441 volunteers with diabetes and followed them for 10 years. Very tight control of blood sugar has led to a reduction of the risk of neuropathy by 60%.

Question: What are the types of diabetic neuropathy?
Answer:

• Diabetic peripheral neuropathy: This is the most common form of diabetic neuropathy and is caused by damage to the peripheral nerves that start from the distal regions and then progress proximally. It usually starts in the feet and is associated with the following symptoms: a) numbness or lack of sensation to pain and temperature in the feet; b) tingling, burning, or prickling sensation; c) sharp pain or cramps; d) extreme sensitivity to touch, even light touch; e) loss of balance and coordination; and f) most of these symptoms are worse during nighttime.
  
  The damage to the peripheral nerves eventually leads to loss of reflexes and to muscle weakness. The feet of the affected patients usually become wider and shorter.
  
  Patients are subject to falls due to gait imbalance because of lack of sensation in the feet and lack of adaptive reflexes.
   
• Autonomic neuropathy: Autonomic neuropathy means damage to the nerves that control involuntary functions, such as heart rate, stomach motility, sweating, vision, and blood pressure control, due to diabetes mellitus.
  
  A.) Urinary and sexual responses
  
  Patients with diabetic autonomic neuropathy have urinary frequency and more prone for urinary tract infection, which if occurs frequently can lead to renal failure. Most of these patients have difficulty emptying their bladder completely.
  
  Also the patients lose sexual responses gradually and become impotent.
  
  B.) Digestive tract.
  
  Patients with autonomic neuropathy secondary to diabetes have low motility of the stomach and of the intestine, leading to alternating constipation and diarrhea, and indigestion.
  
  C.) Cardiovascular system.
  
  Autonomic neuropathy secondary to diabetes can cause lightheadedness whenever the patient stands up due to a drop in blood pressure. Also, it can cause postural headache, and facial flushing.
  
  Profuse or lack of sweating are both common in diabetic autonomic neuropathy.
  
  Patients with autonomic neuropathy have insensitivity to pain and can develop silent myocardial infarction. Also, they can have blunted response to low blood sugar, a matter that may increase the complications of hypoglycemia in these patients.
   
• Focal neuropathy: Patients with diabetic neuropathy can have pinched nerves in different locations, as their nerves are more subjected to pressure induced damage. The most common locations of focal neuropathy are at the wrist, a matter that causes carpal tunnel syndrome, which is much more common in diabetics than normal population. In addition, compression can occur at the elbows, close to the funny bones, leading to numbness in the 4th and 5th fingers, weakness of the handgrips, and wasting of the hand muscles.
   
• Diabetic ocular palsy: Patient with diabetes can have infarction of one of the nerves that move the eyeball, leaving to severe pain behind one or both eyeballs, and difficulty moving the eye to one or the other direction. Fortunately, this is a self-limiting condition, but it can be confused with other more serious intracranial conditions, such as cerebral aneurysm. Initially, the pain should be alleviated with strong painkillers and other important conditions should be excluded.
   
• Diabetic femoral neuropathy: Diabetic commonly develop sudden infarction of the femoral nerves and/or infarction of the network of nerves that come from the back to the legs, leading to severe weakness and wasting of the quadriceps muscles. Again, this is initially a very painful condition and it spontaneously improves most of the time.
   

Question: How do doctors diagnose diabetic neuropathy?
Answer: The diagnosis of diabetic neuropathy is based on the diagnosis of diabetes and on the presence of symptoms that are caused by neuropathy, which we mentioned before.

A simple screening test that we use in the clinical setting is adequate to screen patients who are prone for feet ulcers secondary to diabetic neuropathy. This test uses a nylon filament mounted on a small wood. The filament delivers a standard 10-gram force when touched to the areas of the foot. Patients who cannot sense the pressure from the filament have lost protective sensation and are at risk of developing neuropathic foot ulcers.

Nerve conduction studies are also very useful to determine the type and severity of damage to the nerves in different parts of the body.

Question: How is diabetic neuropathy treated?
Answer: Treatment will basically consist of tight control of blood sugar, symptomatic treatment for pain, fall precautions, and foot care.

• Pain relief: Several agents are useful for pain relief. For mild pain, acetaminophen may help. Most of the time, the patient needs stronger pain medications and these pain medications are different than the regular painkillers. Most of these pain medications are chemical modulators, rather than anti-inflammatory medications. Tricyclic antidepressants, carbamazepine, and more recently Neurontin are all effective if given in the right dosage.
  
  Warm bath, massage, and algesic ointments can all be helpful.
   
• Gastrointestinal problems: For patients with delayed stomach emptying, they may benefit from metoclopramide. This medication enhances the motility of the stomach.
  
  To relieve diarrhea or other bowel symptoms, antibiotics or clonidine may be helpful.
   
• Urinary symptoms: Urinary symptoms are treated by antibiotics if they are caused by infection. If incontinence is a problem, the patient may be advised to urinate at regular times; for example, every 3 hours because they do not feel their bladder when the bladder is full.
   
• Dizziness and weakness: These symptoms are due to a drop in the blood pressure when the patient stands up. Elastic stockings may help. Medications such as fludrocortisone and midodrine may also help for advanced cases.
   
• Foot care: It is very important that patients take good care of their feet to avoid further complications such as osteomyelitis and amputation. Six per thousand patients with diabetes undergo amputation eventually. Diabetic feet are more prone to infection and ulceration.
  
  
  To prevent feet problems, the following procedures are recommended:
  
  * Check your feet and toes daily for any cuts, sores, bruises, bumps, or infection, using a mirror if necessary.
  * Wash feet daily using warm and not hot water. If you have neuropathy, you should test the water temperature with your wrist before putting your feet in the water.
  * Cover you feet with petroleum jelly.
  * Wear thick soft socks and avoid wearing slippery socks.
  * Wear shoes that fit your feet very well and allow your toes to move. Break in new shoes gradually.
  * Examine your shoes before putting them on to make sure they have no tears, sharp edges, or objects in them that might injure your feet.
  * Never go barefoot, especially on the beach, hot sand, or rocks.
  * Cut your toenails straight across.
  * Use an emery board or pumice stone to file away dead skin, but do not remove calluses, which act as a protective padding.
  * Test the water temperature with your elbow before getting in a bath.
  * If you feet are cold at night, wear socks.
  * Avoid sitting with your legs crossed. Crossing your legs can reduce the flow of blood to the feet and also can cause compression on the nerves around the knees.
  * Ask your doctor to check you feet every visit.
  * If you are not able to take care of your own feet, ask your doctor to recommend a podiatrist.

Question: Are there any experimental treatments for diabetic neuropathy?
Answer: Yes, there are several medications that are being tried in the Nerve & Muscle Center of Texas. Currently, several medications are being tested. Aldose reductase inhibitors are agents that prevent the formation of sorbitol, which causes swelling and damage to the nerves, are being tested.

Other General Recommendations:

• Smoking has a deleterious effect on the nerves because it causes vasoconstriction. It is highly recommended that smoking be stopped in patients with diabetic neuropathy.
• Alcohol drinking adds more to the damage that is caused by diabetes on the nerves and it should be avoided.
  
  If you have any questions, please call the Nerve & Muscle Center of Texas, (713) 795-0033.