Diabetic Neuropathy

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 :

  • sensory (detect sensation such as heat, cold, pain)
  • motor (contract muscles to control movement)
  • autonomic (regulate functions we cannot control directly, such as heart rate and digestion)

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.

  1. loss of ability to feel pain and other sensation which leads to neuropathic ulceration.
  2. symptoms of pain, burning, pins and needles or numbness which lead to discomfort (see section on Painful Neuropathy).

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 :

Typical Neuropathic Ulcer
  • painless
  • surrounded by callus
  • associated with good foot pulses (because the circulation is normal)
  • at the bottom of the foot and tips of toes

 

  Neuropathic Ulcer Due to tight shoe straps

 

 

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 :

  • you have had a foot ulcer before
  • you have lost a lot of sensation in the feet when your doctor tested it
  • you do not follow advice to protect your feet with good footwear and hygiene

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.

Before After
call_bef.jpg - 16814 Bytes call_aft.jpg - 16630 Bytes

 

The type of dressing material that we use

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.
The old edict of keeping a wound dry and painting it with antiseptics is no longer thought to be the treatment of choice. Do not clean the ulcer with anything that is too caustic (eg strong Eusol or hydrogen peroxide) because this can damage the tissue further.
A good rule of thumb is not to put anything on the ulcer that you wouldn't put in your eye.

 

A properly dressed wound Packing of wounds should
be avoided as this
increases pressure
at the ulcer site

 

Taking antibiotics if the ulcer is infected. Remember, most foot ulcers are infected.
Many weeks of antibiotics may be required if the ulcer is not completely healed or if there is underlying osteomyelitis.

 

 

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

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.

Contact Cast

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

Deformed toes which are causing
excessive pressure at the tip and at the top.
A prominent metatarsal head that is
preventing an ulcer from healing
Deformed Toes Prominent Metatarsal

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.