Diabetic Neuropathy

by Dr Alison Nankervis – Medical Adviser to DAV

We still don’t fully understand the basic causes of neuropathy. Certain chemical sub-stances accumulate in nerve fibres and affect both the structure and the function of these nerves. Changes to small blood ves-sels supplying nutrients to nerves are also affected and can alter nerve function. It is clear though that nerve damage is closely related to diabetes control and to duration of diabetes. The Diabetes Control and Complication Trial (DCCT) is the most important study to date to have examined the effects of tight blood glucose levels on the development of microvascular complications. The DCCT demonstrated very clearly that good control reduced the chance of both the development and progression of diabetic neuropathy, as well as reducing risks of kidney and eye damage.

Therefore, maintaining tight control of your diabetes is critical in preventing or reducing the impact of neuropathy.
 

Key steps in managing diabetic neuropathy

• Maintain the best possible diabetes control.
• Ensure that your nerves (especially of your feet) are checked annually by your doctor.
• If you have peripheral neuropathy, take scrupulous care of your feet.

Types of neuropathy

Chronic peripheral neuropathy (long-term damage to nerves of the feet, legs and hands) usually involves the sensory nerves (nerves conveying messages of sensation). It is often first noticed as a minor numbness or pins-and-needles of the toes. This loss of sensation can gradually extend to involve the feet and the legs. The hands can also be affected. This pattern of nerve damage is known as ‘glove and stocking’ – for obvious reasons. The major problem resulting from sensory neuropathy is that pressure areas, minor injuries, blisters and ulcers might develop unnoticed. Sometimes burning pain, particularly affecting the front of the legs and often at night, can be very troublesome. Nerves supplying the muscles of the feet can also be damaged, leading to altered function of some of the small foot muscles. This can cause ‘clawing’ of the toes and altered distribution of pressures to the sole of the foot. This can result in problems with pressure areas and possibly ulceration.

Autonomic neuropathy refers to damage to the automatic ‘nerves of the body’ and can cause problems with blood pressure control, the digestive system, bladder and sexual function.

Faintness or dizziness on standing can occur because the walls of the blood vessels lose their tone and the blood pressure falls on changing from a lying or sitting to a standing position. This can sometimes be mistaken for hypoglycaemia. It is often worse if you are taking tablets for high blood pressure.

With autonomic neuropathy, the stomach can also lose its tone and fail to empty properly. This can lead to a feeling of fullness, even several hours after a meal, bloating, nausea and vomiting. The movement of the bowel can be disrupted, causing constipation or diarrhoea. Classically the diarrhoea occurs at night.

The bladder, too, can become ‘floppy’, failing to empty properly and sometimes leading to urine infections or incontinence. Impotence is another common problem and often results from autonomic nerve damage.

Autonomic neuropathy can reduce the body’s response to hypoglycaemia. This results in a loss of symptoms such as sweating, shaking and palpitations and make hypos more difficult to detect.

Treatment of all of these chronic neuropathies is based on treating the symptoms. There is no specific way of preventing or treating neuropathy apart from maintaining ‘normal’ blood glucose levels. A group of drugs called aldase reductase inhibitors can reduce the accumulation of certain chemical substances in the nerves, but have not been shown to be helpful clinically. A promising new treatment involves injection with a substance called ‘nerve growth factor’. This is currently being used in clinical trials around Australia.

Other forms of neuropathy are less common and are not directly related to diabetes control. They generally resolve spontaneously.

Amyotrophy typically causes a deep pain and weakness of the thighs. It usually resolves over 6-12 months.

Individual nerve lesions can affect the nerves of the face or eyes, causing either facial paralysis or double vision. Nerves in the arms and legs can also be affected. Full recovery usually occurs in weeks to months.

The neuropathic foot As a result of peripheral neuropathy, the feet can lose the ability to feel pain, temperature and touch. Muscle balance is often altered. The foot is then at much greater risk of ulcer formation, sometimes ultimately leading to osteomyelitis or gangrene. Care of the neuropathic foot requires meticulous attention, as careful management can prevent problems, such as ulcers, developing. Effective foot care is an essential part of managing diabetic neuropathy.