What is Diabetic Neuropathy?
The best way to prevent neuropathy is to keep blood glucose levels as close to the normal range as possible. Maintaining safe blood glucose levels protects nerves throughout the body.
Diabetic neuropathy means damage of nerve fibres in people with diabetes. The exact cause of this 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. Peripheral neuropathy, also called distal symmetric neuropathy or sensor motor neuropathy is nerve damage in the arms and legs. Feet and legs are likely to be affected before hands and arms. Many people with diabetes have signs of neuropathy that a doctor could note but feel no symptoms themselves. Symptoms of peripheral neuropathy may include
- numbness or insensitivity to pain or temperature
- a tingling, burning, or prickling sensation
- sharp pains or cramps
- extreme sensitivity to touch, even light touch
- loss of balance and coordination
These symptoms are often worse at night.
Any nerve in the body can be damaged however, the most common type is 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. There are different types of nerves in the body: sensory (detect sensation such as heat, cold, pain) , motor (contract muscles to control movement) and autonomic (regulate functions we cannot control directly, such as heart rate and digestion)
Proximal neuropathy, sometimes called lumbosacral plexus neuropathy, femoral neuropathy, or diabetic amyotrophy, starts with pain in the thighs, hips, buttocks, or legs, usually on one side of the body. This type of neuropathy is more common in those with type 2 diabetes and in older adults with diabetes. Proximal neuropathy causes weakness in the legs and the inability to go from a sitting to a standing position without help. Treatment for weakness or pain is usually needed. The length of the recovery period varies, depending on the type of nerve damage.
What problems can be caused by diabetic neuropathy?
Neuropathy can result in two types of problems. Most patients who have neuropathy have one of these problems but some can be affected by both.
- Diabetic Neuropathy (painless). Loss of ability to feel pain and other sensation which can lead to damage and neuropathic ulceration.
- Diabetic Neuropathy (painful). Symptoms of pain, burning, pins and needles or numbness which lead to discomfort.
Diabetic Neuropathy (Painless)
A typical neuropathic ulcer is shown in the figure below. Patients with neuropathy (often frequently) lose their sensation of pain. As a result, they exert a lot of pressure at one spot under the foot when they walk, being unaware of any discomfort. Callous will build up over the overloaded area without causing discomfort. The pressure becomes so high that eventually it can cause a breakdown of tissues and ulceration. The patient may not notice any pain, or they may become aware of the problem only once the ulceration is well advanced.
A typical neuropathic ulcer is
- painless and moist
- surrounded by callus
- associated with good foot pulses (because the circulation is normal)
- at the bottom of the foot and tips of toes.
- Neuropathic ulcers that occur elsewhere in the foot are usually due to footwear that is too tight. This image shows a neuropathic ulcer caused by shoe straps that were too tight
Are you at high risk of developing a neuropathic ulcer?
Remember that the absence of pain in the feet does not mean you are not necessarily at risk, while conversely the presence of pain in the feet does not necessarily mean you are facing ulceration and amputation. In a sense every person with diabetes has increased risk of developing foot ulceration and needs to take precautions to prevent it from occurring. However, some people have very low risk and some people have very high risk. Measuring the risk helps the patient and their podiatrist or doctor determine appropriate strategies, without being too relaxed or too rigid. Patients at low risk only need general advice. Patients at high risk need detailed, specific and practical foot care instruction.
The overall risk of an individual developing a diabetic foot ulcer is determined by a combination of factors. In general, the risk is higher if:
- Neuropathy is more severe (greater loss of sensation)
- Peripheral vascular disease is more severe (less blood supply to bring adequate oxygen to repair tissue damage)
- There are coexisting abnormalities of the shape of the foot which make the local effects of neuropathy or vascular disease more severe (an increases in local pressure and callus)
- The person is unable to practice reasonable self care to maintain general condition of the feet and to prevent trauma (greater chance of damaging the feet)
- The diabetic control is very poor (greater susceptibility to infection and poor wound healing)
- There is a past history of foot ulceration due to diabetes (the above factors often persist)
What sort of treatment is required for a neuropathic ulcer?
The following are basic guidelines for the management of a neuropathic ulcer:
- Remove the precipitating cause e.g. replace shoes that are too tight. Remove any callous or hard skin regularly to relieve pressure. This will probably need 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 callous.
- It is better for healing if the wound is kept moist under foam dressing which protects the ulcer from further trauma while still allowing oxygen to get through.
The previous practice of keeping a wound dry and painting it with antiseptics is no longer thought to be the optimum application. Do not clean the ulcer with anything that is too caustic (e.g. strong Eusol or hydrogen peroxide) because this can damage the tissue further.
- Avoid packing of wounds as this will increase pressure at the ulcer site. Antibiotics should be prescribed if the ulcer is infected. Generally, most foot ulcers are infected.
Long standing antibiotic therapy may be required if the ulcer is not completely healed or if there is underlying osteomyelitis.
- Elevate the legs and 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).
- The use of an Orthowedge
An Orthowedge is a temporary shoe designed to reduce pressure at the front of the foot where most of the neuropathic ulcers are situated. If an ulcer is not healing with the use of conservative measures the use of an orthowedge may be required.
- Using a Contact Cast to heal a neuropathic ulcer.
Sometimes the application of contact casting (a cast not unlike what is used to treat a fracture lined with a padding material) can drastically reduce pressure and promote the healing process.
- As a last measure, surgical intervention may be required. Bony deformities causing excessive pressure on the ulcerating area may need to be removed.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 which are causing excessive pressure at the tip and at the top.
A prominent metatarsal head that is preventing an ulcer from healing.
Although blood supply is normal in a purely neuropathic ulcer, it is not uncommon for many ulcers to be neuro-ischaemic In other words, an ulcer affected by a combination of impaired nerve function and poor blood supply. Appropriate assessment should reveal any vascular insufficiency contributing to the ulcer.
Diabetic Neuropathy (Painful)
The majority of people with neuropathy suffer with loss of sensation and therefore no painful foot symptoms. Approximately 4-7% of patients with diabetes suffer chronic, often distressing symptoms of pain, pins and needles or numbness in their feet.
Why do people get painful neuropathy?
This question is still the subject of ongoing research. People with poorly controlled long term diabetes appear more likely to get chronic painful neuropathy. Many patients with reasonably well controlled diabetes are also experiencing pain.
Painful symptoms can be transient and may often spontaneously disappear, particularly, once the blood glucose has stabilised for a few months. In these acute situations, once symptoms have persisted for more than 12 months, they are less likely to disappear on their own. Although good blood glucose control is important, striving for very tight blood glucose control is less likely to make the painful symptoms get better when they have been present for this length of time.
Amongst theories suggested to explain why chronic pain or symptoms develop are:
- High blood glucose resulting in changes to the nerve fibres resulting in abnormal nerve signals.
- High blood glucose resulting in changes to blood vessels which supply the nerves.
- Unknown factors releasing chemicals that irritate the nerves and activate pain receptors.
Common symptoms reported include:
- Burning, feeling like the feet are on fire.
- Freezing, like the feet are on ice, although they may feel warm to touch
- Stabbing, like sharp knives
- Some even like an electric shock
People with painful neuropathy may also complain of:
- Feeling pain from a stimulus that would not normally be painful, e.g. wearing shoes or having bed sheets touching the feet
- Hyperalgaesia which means having an exaggerated response to a stimulus which is normally painful. (Often seen in response to heat).
- A feeling of tightness or pressure around the feet
- Vibration or tingling
Does the pain increase my risk of serious foot problems or amputation?
Not necessarily. If you have normal sensation and good circulation, having pain on its own will not increase your risk of foot problems. This is important, as often just knowing this will help to ease the distress. However, if you also have sensory loss or poor circulation in addition to pain, your risk of foot problems is increased and you need to take proper care of your feet. See section on Foot Care for People with High Risk Feet.
It is important to determine if the pain is due to diabetes or some other cause. Pain due to diabetes is usually:
- present in both feet
- equally severe in each foot
- often, but not always, worse at night
If the pain is in one foot only, it may well be from another cause such as arthritis, spinal problems, other neuropathies or peripheral vascular disease. Appropriate investigation should clarify the cause.
- If diabetes is determined to be the cause, and is sufficiently distressing to warrant treatment, there are a number of options available. Unfortunately, neuropathic pain is not easy to treat and not all treatments are helpful for all people. It may be a case of trial and error with different treatments or combinations to achieve acceptable symptom relief.
- Treatment first involves bringing blood glucose levels within the normal range. Good blood glucose control may help prevent or delay the onset of further problems.
- Foot care is an important part of treatment. People with neuropathy need to inspect their feet daily for any injuries. Untreated injuries increase the risk of infected foot sores and amputation.
- Treatment also includes pain relief and other medications as needed, depending on the type of nerve damage.
- Smoking increases the risk of foot problems and amputation. A health care provider may be able to provide help with quitting.
How are diabetic neuropathies treated?
The first treatment step is to bring blood glucose levels within the normal range to help prevent further nerve damage. Blood glucose monitoring, meal planning, physical activity, and diabetes medicines or insulin will help control blood glucose levels. Symptoms may get worse when blood glucose is first brought under control, but over time, maintaining lower blood glucose levels helps lessen symptoms. Good blood glucose control may also help prevent or delay the onset of further problems. As scientists learn more about the underlying causes of neuropathy, new treatments may become available to help slow, prevent, or even reverse nerve damage.
As described in the following sections, additional treatment depends on the type of nerve problem and symptom.
Doctors usually treat painful diabetic neuropathy with oral medications, although other types of treatments may help some people. People with severe nerve pain may benefit from a combination of medications or treatments and should consider talking with a health care provider about treatment options.
Medications used to help relieve diabetic nerve pain include:
- Tricyclic antidepressants, such as amitriptyline, imipramine, and desipramine (Norpramin, Pertofrane) These agents are the tried and tested treatment for neuropathic pain. They are helpful in many cases but their use is often limited by side effects such as urine retention, dry mouth and daytime drowsiness, although some newer preparations are less likely to have these effects. They are usually taken at night, which helps to improve sleep. They should be used in caution with people with glaucoma or the elderly.
- other types of antidepressants, such as duloxetine (Cymbalta), venlafaxine, bupropion (Wellbutrin), paroxetine (Paxil), and citalopram (Celexa) Antidepressants in other classes may also be proven to be successful, but at the moment there are few scientific studies to support their use
- anticonvulsants, such as pregabalin (Lyrica), gabapentin (Gabarone, Neurontin), carbamazepine, and lamotrigine (Lamictal) have been approved for treating painful diabetic peripheral neuropathy.
- opioids and opioid-like drugs, such as controlled-release oxycodone, an opioid; and tramadol (Ultram), an opoid that also acts as an antidepressant
- Duloxetine and pregabalin People do not have to be depressed for an antidepressant to help relieve their nerve pain. All medications have side effects, and some are not recommended for use in older adults or those with heart disease. Because over-the-counter pain medicines such as ibuprofen may not work well for treating most nerve pain and can have serious side effects, some experts recommend avoiding these medications.
- For minor pain, simple analgaesics, such as paracetamol or aspirin are often helpful. However, until now, it has been generally accepted that opiates or narcotic agents are not helpful in relieving neuropathic pain. A newer non-narcotic agent known has Tramadol, has been shown in a few small trials to have promising results.
- Treatments that are applied to the skin typically to the feet include capsaicin cream and lidocaine patches (Lidoderm, Lidopain). It is important to note that capsaicin may cause burning or discomfort when first applied. Treatment should persist for at least a month to determine its effectiveness Studies suggest that nitrate sprays or patches for the feet may relieve pain. Studies of alpha-lipoic acid, an antioxidant, and evening primrose oil suggest they may help relieve symptoms and improve nerve function in some patients.
- A device called a bed cradle can keep sheets and blankets from touching sensitive feet and legs. Acupuncture, biofeedback, or physical therapy may help relieve pain in some people. Treatments that involve electrical nerve stimulation, magnetic therapy, and laser or light therapy may be helpful but need further study. Researchers are also studying several new therapies in clinical trials
- Acupuncture may be an option particularly suitable for people who do not like taking tablets. It is thought to work by suppressing painful signals from reaching the brain. Some practitioners use an electric current through the needles
Chronic pain is not just a product of physical abnormalities. Psychological factors have significant influence over how an individual perceives and deals with pain. As such, psychological support is integral to the treatment of chronic pain. Formal assessment and counseling should be made available to people who have difficulties in coping with their pain.