What is diabetic neuropathy ? What is a neuropathic ulcer and how do you treat it ?
What is diabetic neuropathy ?
Diabetic neuropathy means damage of nerve fibres in people with diabetes. How the nerves are injured is not entirely clear but research suggests that high blood glucose changes the metabolism of nerve cells and causes reduced blood flow to the nerve. There are different types of nerves in the body. These can be grouped as :
The most common type of diabetic neuropathy affects the nerves in the legs and is usually known as peripheral neuropathy. This is the type of neuropathy that causes foot problems. It affects mainly the sensory nerves although the motor and autonomic nerves can also be involved with important consequences.
What problems can be caused by diabetic neuropathy ?
Neuropathy can result in two sets of what superficially appear to be contradictory problems. Most patients who have neuropathy have one of these problems but some can be affected by both.
A typical neuropathic ulcer is shown in the figure below. Patients with neuropathy lose their sensation of pain. As a result, they exert a lot of pressure at one spot under the foot when they walk, building up a callus at that site without causing discomfort. The pressure becomes so high that eventually it causes breakdown of tissues and ulceration. The patient hardly notices any pain.
Therefore a typical neuropathic ulcer is :
Please note if neuropathic ulcers occur elsewhere in the foot, it is usually due to footwear that is too tight. This image is of a neuropathic ulcer caused by shoe straps that were too tight
Are you at high risk of developing a neuropathic ulcer?
This will be dealt with more thoroughly in the section on "Foot examination- Checking your risk of developing a diabetic foot ulcer".
Briefly, you are at risk if :
Remember that even if you have no pain in the feet, it does not mean you are not at risk. On the other hand, just because you have pain in the feet does not necessarily mean you are facing ulceration and amputation.
What sort of treatment is required for a neuropathic ulcer ?
This is dealt with in greater detail under the technical info button at the bottom of this page. In principle, these are the important measures:
Remove the precipitating cause eg. replace shoes that are too tight. Remove the callus regularly to relieve pressure. This usually needs to be done every week. It is best carried out by a podiatrist accustomed to treating diabetic foot ulcers because experience is important to ensure adequate removal of callus. See image below which shows adequate removal of callus.
It is better for healing if the wound is kept moist under
a foam dressing which protects the ulcer from further trauma
and yet allows oxygen to get through.
Taking antibiotics if the ulcer is infected. Remember, most
foot ulcers are infected.
Rest the feet as much as possible because this helps to reduce pressure on the ulcer. Walking is not a good exercise for someone who has a neuropathic ulcer (or someone who is at great risk of developing one).
Wearing an Orthowedge
If a neuropathic ulcer does not heal with the above conservative measures, more specialised methods of relieving the pressure may be needed. These may include wearing an Orthowedge designed to reduce pressure at the front of the foot where most of the neuropathic ulcers are situated.
Using a Contact Cast to heal a neuropathic ulcer.
Sometimes application of contact casting (a special form of cast not unlike what is used to treat a fracture, except it is better padded inside) can promote ulcer healing, again by reducing pressure on the ulcer.
Sometimes when all the above measures have been tried but the ulcer still does not heal, it may be necessary to ask a surgeon to correct some foot deformities which are causing too much pressure. Examples of this include removal of a clawed toe or a prominent metatarsal head
Although blood supply is normal in a purely neuropathic ulcer, in real life many ulcers are neuro-ischaemic. In other words, there is a combination of impaired nerve function and poor blood supply. Therefore it would also be wise to check that blood supply is normal. Sometimes a neuropathic ulcer will only heal when blood supply is improved.