What is diabetic neuropathy?
Neuropathy in diabetes is also called diabetic nerve damage or diabetic neuropathy. People with diabetes mellitus can develop this complication, which can cause temporary or permanent damage to nerve tissue.
Some people with neuropathy in diabetes have no symptoms, while others experience symptoms that usually develop gradually over many years. Symptoms will depend on which nerves are affected.
Peripheral neuropathy affects the peripheries of the body — usually the feet and legs, and sometimes the hands and arms. It generally affects both sides of the body, and mostly affects the sensory nerves (nerves responsible for the sensations of touch, pain and temperature).
- numbness, or loss of sensation progressing over time from the toes up;
- pain or burning in the feet;
- aching or shooting pains in the feet and legs, especially at night; and
- muscle weakness.
Peripheral neuropathy is the most common type of diabetic neuropathy.
Autonomic neuropathy is when the nerves that control the automatic functions of the body are damaged. Autonomic neuropathy can affect digestion, bowel and bladder function, sexual response and regulation of blood pressure.
- diarrhoea (often at night), constipation or both;
- indigestion, nausea and vomiting;
- difficulty swallowing;
- loss of bladder control;
- changes in vision;
- erectile dysfunction and problems with ejaculation;
- vaginal dryness and sexual dysfunction;
- low blood pressure when standing up (causing giddiness or light-headedness);
- inability to sweat or excessive sweating; and
- hypoglycaemia unawareness (when people stop experiencing symptoms associated with hypoglycaemia and therefore can’t recognise when their blood sugar levels are too low).
A type of neuropathy called proximal neuropathy (also called diabetic amyotrophy or radiculoplexus neuropathy) affects the hips and thighs in people with diabetes. It causes:
- sudden onset of pain in the pelvis, buttocks and thigh (usually one-sided);
- pain that is often worse at night, which affects sleep; and
- weakness of hip and thigh muscles, which causes difficulty getting up from a sitting position.
Symptoms usually improve or resolve completely over time.
Nerve damage that affects a particular nerve is called focal neuropathy or mononeuropathy. The symptoms, which usually improve or disappear over time, depend on the location of the nerve affected and can include:
- sudden pain;
- muscle weakness;
- problems with vision and eye movement; or
- facial paralysis (often seen with a drooping eyelid or mouth).
What causes neuropathy in diabetes?
Injury to the nerves in diabetes is caused by a low blood flow to nerve tissue and high blood sugar levels. Neuropathy is more likely to result if blood glucose levels are not managed effectively.
Some people with diabetes never develop neuropathy while others may develop this condition relatively early. For people with type 2 diabetes, nerve damage may also have already occurred before diabetes was diagnosed and treatment begun.
The risk of developing diabetic neuropathy depends on:
- your age;
- how long you have had diabetes; and
- how well your blood glucose levels have been controlled.
Other factors that can contribute to your risk include:
- high blood pressure;
- abnormal cholesterol levels;
- overweight and obesity;
- smoking; and
- alcohol abuse.
Peripheral neuropathy and risk of injury
In more advanced cases of diabetic neuropathy, there is an increased risk of injury because of loss of sensation and/or motor function. When complete loss of sensation occurs in the feet, people may not be aware of injuries occurring to the feet and consequently fail to look after them properly.
Because of poor circulation, many injuries in people with diabetes heal very slowly or not at all. Even minor injuries can lead to serious infection, ulcers and even gangrene, which may then mean the amputation of toes, feet and other infected parts.
Loss of temperature sensation is also a significant risk factor for injury in people with diabetes. This can result in a person being unaware that the bath water they are stepping into is scalding them. They may also be at risk of developing severe burns after sitting too close to a heater.
Tests and diagnosis
If you have diabetes, your doctor should regularly check for symptoms and signs of diabetic neuropathy by taking a history and performing a physical examination.
Occasionally, nerve conduction studies and electromyography (which evaluate the electrical activity in nerves and muscles) are used to determine the extent of nerve damage.
Treatment of neuropathy in diabetes
The treatment of neuropathy in diabetes usually involves good control of blood glucose levels. Tight control of the amount of glucose in the bloodstream has been shown to reduce the risk of neuropathy, slow its progress and help improve symptoms.
Specific treatment will depend on the type of nerve damage and your symptoms.
Although diabetic neuropathy often causes loss of sensation, it can occasionally cause pain, especially in the feet and legs. This pain is often distressing, particularly at night when it can prevent sleep. Unfortunately, conventional analgesics are not often useful in this type of pain, and other types of medicines may be needed.
Medicines that may be useful in treating painful neuropathy include:
- antidepressant medicines, such as amitriptyline and duloxetine (brand names include Andepra, Cymbalta);
- anti-seizure medicine such as gabapentin (e.g. Gantin, Neurontin, Nupentin) and pregabalin (e.g. Lyrica); and
- capsaicin cream (a pain-relieving cream, e.g. Zostrix HP cream).
Your doctor will be able to discuss these pain relief options with you.
People with peripheral neuropathy should:
- wear well-fitting shoes or some type of foot protection as much as possible;
- check their feet every day to detect foot problems (such as blisters or breaks in the skin) early; and
- have regular foot checks by a doctor or podiatrist.
Even very small injuries should be attended to immediately to prevent the development of ulcers and serious infections.