What is neuropathic pain?
Usually, pain is felt when special nerve endings sense that something is wrong with your body and send pain signals to your spinal cord and brain. Neuropathic pain occurs when the nerves themselves are damaged by disease or injury, causing them to misfire and send pain signals to the brain. The resulting pain is often severe and can be difficult to treat.
Neuropathic pain is usually described as shooting, stabbing or burning, sometimes it feels like an electrical shock, and is often worse at night than during the day. The pain may be constant or it may come and go, and it may be accompanied by tingling sensations or numbness.
People with neuropathic pain are often extremely sensitive to painful stimuli. They may also have increased sensitivity to touch or cold, and may perceive non-painful stimuli, such as light touch or gentle brushing of the skin, as severe pain.
What causes neuropathic pain?
Neuropathic pain is caused by damage to, or dysfunction of, the nervous system. The pain can be due to problems in the central nervous system (the brain or spinal cord) or the peripheral nervous system (the nerves in the rest of the body — i.e. the nerves in your face, arms, legs and torso).
While doctors are sometimes unable to pinpoint the exact cause of neuropathic pain, there are several known causes, including:
- vitamin B12 or thiamine (vitamin B1) deficiency;
- alcohol abuse;
- multiple sclerosis;
- nerve compression or invasion by a tumour;
- certain medicines;
- infections such as shingles and HIV/AIDS; and
Some examples of neuropathic pain include:
Painful diabetic peripheral neuropathy
Diabetes can damage the peripheral nerves, especially those in the legs and feet, causing pain as well as numbness and tingling.
Trigeminal neuralgia is a disorder of the trigeminal nerve — the nerve that supplies sensation to the face and controls some of the muscles involved in chewing. It causes episodes of severe facial pain that last from a couple of seconds to several minutes.
About one in every 5 people with shingles (a painful rash also known as herpes zoster) develops post-herpetic neuralgia — ongoing pain in the area that was affected by the rash. It occurs when the shingles virus damages the underlying nerves, and the resulting pain can last for months or years.
Phantom limb pain
This condition affects people who have had an arm or leg amputated, causing pain or discomfort in the area of the now-missing limb. The exact cause of phantom limb pain is not known, but it is thought to be due to changes in both the peripheral and central nervous systems following amputation.
How is neuropathic pain diagnosed?
If your doctor suspects you have neuropathic pain, he or she will ask about the pain and perform a physical examination, testing the nerves in the affected area. You may need to have blood tests, nerve conduction studies (to measure how quickly your nerves can carry electrical signals) or an MRI scan. Sometimes a nerve biopsy is needed to examine a small portion of nerve fibres for any abnormalities.
Are there any treatments available?
In general, if you have neuropathic pain, your doctor will most likely suggest you try regular pain medicines such as aspirin, paracetamol or a non-steroidal anti-inflammatory drug (NSAID) to start with. But while they are worth trying, these medicines may not always relieve neuropathic pain.
The good news is that there are different medicines available that can help treat this type of pain. Not all of the medicines are available on the PBS, however, your doctor will be able to guide you. The medicines include:
A class of antidepressant medicines known as tricyclic antidepressants (tricyclics) has been found to relieve neuropathic pain in many people. These medicines have a pain-relieving effect that is separate from their antidepressant effect, and may be especially useful in relieving constant, burning pain. Amitriptyline is the most commonly used tricyclic for treating neuropathic pain. It seems to be the most effective pain reliever for this condition, but it is not always well tolerated because of its side effects.
Anticonvulsant medicines — the same medicines that are used to control seizures in people with epilepsy — can also be effective in treating neuropathic pain, and work by slowing or blocking uncontrolled pain signals. Anticonvulsants may be better than tricyclics for treating sharp, shooting neuropathic pain.
Gabapentin (e.g. Neurontin) and pregabalin (Lyrica) are anticonvulsant medicines that can relieve neuropathic pain. They have been found to be useful in treating painful diabetic neuropathy and post-herpetic neuralgia.
Carbamazepine (e.g. Tegretol, Teril) is another type of anticonvulsant medicine that can be used. It is usually the preferred choice for trigeminal neuralgia, and has been shown to have some effect in treating painful diabetic neuropathy.
Sodium valproate may be tried if the above anticonvulsants fail to relieve pain, or are not well tolerated due to side effects.
If tricyclics and anticonvulsants have not relieved your pain, you doctor may suggest you try other types of medicine, which may need to be prescribed by a specialist pain physician. They include:
Antiarrhythmics (e.g. mexiletine or flecainide) are normally used to stabilise abnormal heart rhythms, but are sometimes effective in controlling neuropathic pain. People with certain heart problems may not be able to use these medicines.
Clonidine is a medicine that is usually used to control high blood pressure, but may relieve pain in some people.
Local anaesthetics (e.g. lignocaine cream or skin patches) and capsaicin cream (which contains a substance extracted from red chilli peppers) may also be effective in treating some types of neuropathic pain, such as post-herpetic neuralgia. Strong pain relievers such as tramadol (e.g. Tramal, Tramedo, Zydol), morphine and oxycodone (e.g. Endone); anaesthetic medicines (such as ketamine); and injections of medicines directly into the spine can also be tried.
There is also another type of antidepressant medicine — a serotonin and noradrenaline reuptake inhibitor (SNRI) — called duloxetine (brand name Cymbalta) which can be used to treat painful diabetic peripheral neuropathy.
A combination of several medicines can be effective for some people, especially those who have a partial response to one or more medicines.
Are there any other treatments that can be tried?
There are some other treatments that may help to control neuropathic pain, including:
- relaxation techniques, which are used to reduce any muscle tension that is contributing to pain;
- psychological treatments, such as cognitive behavioural therapy (CBT), which can help you gain a sense of control over pain and reduce distress; and
- transcutaneous electrical nerve stimulation (TENS), which uses mild electrical currents (from electrodes that are taped to the skin near the site of the pain) to block the transmission of pain sensations to your brain.
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4. Australian Pain Society. Evidence-based recommendations for the pharmacological management of neuropathic pain. Position Statement, June 2008. Available at: http://www.apsoc.org.au/owner/files/cz4s7w.pdf (accessed 2010, May 11)