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DIABETIC NERVE DAMAGE - DIABETIC NEUROPATHY

What is it ?

After diabetes has been present for only a short time, chemical and other changes can occur in the nerves of your body. These changes can cause either temporary or more permanent nerve damage. Such damage interferes with the conduction of impulses through the nerves. There may be no symptoms of this whatsoever. Conversely, a symptom of nerve damage may be the very first sign that diabetes has developed. Double vision may occur from damage to the nerves controlling eye movements; or one side of the face may droop due to damage to the facial nerve.

Foot movements on one side may become weak (foot drop), or there may be generalised weakness of all muscles in the body with fatigue. This is called motor neuropathy. The changes often reverse quite quickly when diabetes is brought under control with treatment. Some of the most common symptoms affect feeling. After several years of diabetes, numbness and tingling may occur, particularly in the feet.

You may not be aware of cuts, blisters or infections, particularly if they are on the soles of the feet. Indeed, an inability to feel pain may be a reason for a unrecognised cut or injury becoming infected. Some people with neuropathy develop gnawing, sharp or stabbing nerve pains, which can be most unpleasant. Even joints can become damaged, deformed and swollen if the nerves which supply them are damaged. It is the ankle which is particularly at risk. Charcot’s neuropathy or neuro-arthropathy are terms used to describe this uncommon but serious complication. All these conditions are all referred to as different types of sensory neuropathy.

In addition, more subtle (but very important) damage can occur to so-called autonomic nerves. These nerves do not control movement or feeling, but regulate many of the body’s functions of which we are mostly unaware - until something goes seriously wrong. The bladder may not empty properly causing a wide variety of urinary symptoms, including a poor stream and a need to pass urine either less often or more often than usual. In males, impotence may occur. Blood pressure control may be lost, with a fall of pressure on standing, which causes giddiness or fainting. Even the bowel may be affected, with episodes of constipation, diarrhoea or incontinence.

How does it occur ?

When levels of blood glucose run above normal, the glucose which leaks into nerve cells is converted to chemicals which damage the nerve fibres. These then do not function properly. Early changes may be reversible, if blood glucose levels are brought under control. However, after a period of time, the nerve becomes permanently damaged: little or no recovery of function is then possible. In addition to these chemical changes, the tiny blood vessels, which feed the nerves may become blocked. It is then a lack of oxygen, which causes the nerve damage.

Why does it occur ?

Some people with diabetes seem particularly prone to nerve damage: others seem more resistant. This may be due to inborn differences in the way that glucose is processed in nerve cells. It is not known why different nerves are affected in different people. Nerve damage is much more common if diabetes is not well controlled. In these people, it is often too late to reverse the damage in the nerves once symptoms have developed. However, your doctor will regularly check your ankle reflexes and your ability to feel touch, pain and vibration. If such changes are present, it may be still possible to halt the damage.

Treatment Involved

Some additional tests may be carried out. The speed of conduction of signals through the motor and sensory nerves can be measured, and the completeness of bladder emptying can also be checked in a number of ways. Once neuropathy is diagnosed, the first step will be to improve control of your blood glucose levels. This will mean attention to diet and exercise, and a probable change in the medication insulin or tablets. Your doctor will probably want you to run blood glucose levels that are mostly or always below 10mmol/litre (180mg/100ml), and lower than this before meals. He or she will pay particular attention to the blood test called haemoglobin A1c (HbA1c) levels. This indicates your overall level of glucose control over the previous 10 weeks or so. You will probably be advised to aim for levels below 7%.

If your feet are affected, you will be advised about avoiding barefoot walking and ensuring well-fitting shoes, which do not cause pressure. Your foot care should ideally be carried out by a registered chiropodist (podiatrist), and you will advised against self-treatment of any foot conditions. Even standard toenail care could be hazardous, especially if your eyesight is not perfect. Any minor injury could become infected, with ulceration and even infection of the underlying bone (osteomyelitis). Regular inspection of your feet will help to reduce these risks, and X-rays will be checked repeatedly if any chronic foot infection is present.. No drug is yet available to block the abnormal chemical reactions, which result in damages to nerves. Good blood glucose control is at present the only way of limiting nerve damage. Unpleasant tingling and pain may be helped by using low doses of anti-depressant drugs. Anti-convulsants (as used in epilepsy) reduce the sensitivity of nerve endings, and are also helpful in some cases.

During Treatment

If your bladder has been affected, your doctor may suggest a technique called triple voiding - passing urine again on two further occasions, five minutes apart, after each visit to the toilet. Completely emptying the bladder in this way helps to reduce the risk of infection. Giddiness and fainting due to blood pressure falls can be helped by a variety of medications, which raise the blood pressure. Sometimes, compression stockings on the legs help. Impotence treatment is dealt with separately. Bowel problems are treated either with drugs to control bowel activity or by antibiotics. These control bacterial growth in the bowel, which contributes to the diarrhoea, if present. The aim of better blood glucose control may increase the risk of low blood glucose levels (hypoglycaemia). In-between snacks and keeping emergency glucose sweets to hand both help to reduce this risk. The side-effects of other drugs is dealt with elsewhere.

After Treatment

Ongoing good diabetic control, together with care of your feet are essential if you wish to avoid further problems.

If Left Untreated

You would be at risk of worsening nerve symptoms. Many research studies have shown that better blood glucose control can markedly reduce the risk of significant nerve damage and it consequences. This has been shown separately for both type 1 diabetes (DCCT study) and for type 2 diabetes (UKPDS). Once neuropathy is established, a failure to treat the early problems of the feet can result in devastating infection, even leading to amputation.

Effects on Family

There is little that anyone other than the person with diabetes can do to help. Your family may however be happy to remind you about the details of foot care (which can be easily forgotten), and the need for regular medical checks to screen for the earliest signs of nerve damage.