By Lori Montgomery, MD, CCFP
There are many definitions of neuropathic (say: noor-uh-PATH-ik) pain. This makes diagnosing and treating it somewhat difficult. The International Association for the Study of Pain defines neuropathic pain as pain that is caused by a problem in the nervous system. This is a very broad definition. In general, it can be split into two types: peripheral and central.
Peripheral neuropathic pain
Peripheral neuropathic pain is pain that happens in the nerves outside the spinal cord, like the ones in your wrist in the case of carpal tunnel syndrome, or in your skin in the case of diabetic neuropathy. This can be a result of:
- a systemic (that affects the whole body) problem like diabetes
- alcohol abuse
- medicine side effect (in which an environment is created that is toxic to nerves)
- a more specific problem like a tumour on a nerve
- traumatic injury to a nerve
Central neuropathic pain
Central neuropathic pain arises in the brain or spinal cord, such as the pain that happens after a spinal cord injury or a stroke. In both peripheral and central neuropathic pain, the problem is a malfunction (not working how they should) in the nerves themselves. This causes them to transmit pain signals for no useful purpose.
Signs and symptoms
Fibromyalgia affects three to six percent (3 to 6 out of 100) of the population. It varies in severity. Some patients are very mildly affected, while others are very disabled. Some possible symptoms are:
- pain which may be burning, shooting, stabbing, or electric shock-like
- itching, tingling, or pins and needles sensations
- very sensitive skin as if you have a bad sunburn
- very sensitive to heat or cold
- specific muscle weakness
- muscle twitching
- sleep disruption (because pain is often worst at night)
There are more than 100 causes of neuropathic pain. Here are some examples:
- alcohol abuse
- medicine side effects (for example, certain anti-cancer drugs)
- certain vitamin deficiencies
- diabetic neuropathy
- pressure from a tumour
- repetitive stress (like carpal tunnel syndrome)
- post-herpetic neuralgia
The tests that are needed will depend on how you describe the pain and what other medical conditions you have.
Often, blood tests will be useful to look for things like diabetes, thyroid disease, or vitamin deficiencies.
The simplest test is a small filament that your doctor can use in the office to test your sensation. The device applies a constant amount of pressure, so that your doctor can compare your skin sensitivity to that of a person without neuropathy. If you are diabetic, this may be the only other test that needs to be done.
Quantitative sensory testing (QST)
Quantitative sensory testing (QST) can be used to make note of changes in your condition over time. This test checks your sensitivity to light touch, pinprick, pressure, vibration, and temperature. It is not often needed to make decisions about treatment, but is helpful in research studies to look at disease progression.
Nerve conduction studies (NCS) or electromyography (EMG)
Nerve conduction studies (NCS) or electromyography (EMG): these tests check how well an electrical signal is being transmitted through a nerve, or how well the muscles respond to the nerve signal. These tests are sometimes needed to help narrow down the diagnosis.
There are a number of medicines that are used to control nerve pain. Some patients may benefit from:
- tricyclic antidepressants (such as amitriptyline or nortriptyline)
- gabapentin or pregabalin
- tramadol or other opioid-like medicines (such as morphine)
- serotonin-norepinephrine reuptake inhibitors (such as venlafaxine or duloxetine)
- over-the-counter creams containing capsaicin
- gels or creams that include a local anaesthetic such as lidocaine.
These can only be used over small areas of skin.
Acupuncture and TENS
Some patients find things like acupuncture or transcutaneous electrical nerve stimulation (TENS) helpful as well.
Studies have shown that non-drug therapies can help to reduce pain levels and enhance pain coping. These include:
- activity pacing
- cognitive behavioural
These self-management strategies can help you to improve your function so you can do more and enjoy life more.
Dworkin RH, et al. Advances in neuropathic pain: Diagnosis, mechanisms, and treatment recommendations. Archives of Neurology. 2003;60:1524-34.
National Institute of Neurological Disorders and Stroke, National Institutes of Health. Peripheral neuropathy fact sheet (www.ninds.nih.gov). Last update November 19, 2008.