Overview
Of the many types of pain that can affect the head and neck, perhaps the most confusing and difficult to diagnose are a group of maladies called neuropathic pain disorders. Neuropathic pain disorders arise from the nervous system and often are chronic.

The nervous system can be divided into two general parts; the central portion, which includes the brain and spinal cord and the peripheral part, which includes the nerves that go to the outlying areas of the body such as the arms, legs, trunk, face and teeth. The peripheral nerves involved with neuropathic pain provide sensation (touch, heat, chemical or pain) to a particular area. The nerve courses its way back to the spinal cord where it meets up with a second nerve that extends up the spinal cord to the brain. There, a new nerve may continue to carry the message to other parts of the brain where the message interpreted as pain and is acted upon. The brain has many complex chemical mechanisms to enhance or shut down information streaming into it.

If a peripheral nerve is injured — say a tooth has a nerve injury from decay and subsequent root canal — you might correctly expect that the tooth would be sore for several days. Sometimes, however, the tooth continues to hurt for months and even years. Even more perplexing is that you might have the tooth extracted and it may continue to hurt as if it were still there.

Science has shown that after a peripheral nerve is injured, there can be permanent changes in the area where that nerve was first injured, in the area where it meets the spinal cord and on up the chain into the brain. These changes can result in continued pain, despite normal healing in the area, in our example here, the tooth.

Research has shown that the nervous system can undergo changes both in the peripheral portion and — even more surprisingly — in the central portion so that the persistent pain may come from either one or both parts. This is a phenomenon we call "plasticity" or the ability of the nervous system to be altered. The brain continues to perceive that the area that was first injured is the area that is painful.

The pains that result can vary, but often times will have several qualities that distinguish them from other pains. Often, the patient complains that the pain just happens by itself, or that light touch or hot or cold stimulation triggers the pain. Sometimes it is hard for the patient to figure out just where the pain is coming from. It may seem that there is a general area that is painful. The pain can vary from a general nagging dull ache to a sharp stabbing shock like pain; we call this kind of sharp pain "paroxysmal."

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Getting Help/What to Expect
Patients with neuropathic pain often visit many doctors and undergo many tests, all of which are negative. Even more frustrating and upsetting to patients is that they undergo useless treatments. In the mouth, this may include gum surgery, root canal and even extraction — these procedures only result in occasional temporary relief, no relief or even worse pain.

Persistent pain should be evaluated by a physician, usually a neurologist or anesthesiologist specially trained in pain management, a dentist, or in the case of the head and neck, an orofacial pain expert. The doctor will perform a comprehensive evaluation, which may include a thorough history, examination and will order any diagnostics tests that are appropriate.

The history should include recording of the exact nature of the pain and other symptoms you may have, the history leading up to the persistent pain, past doctors seen, treatments provided and a list of medications you have taken with the results and/or any complications.

The examination includes pressing on different areas of the head, neck and inside the mouth, measurements and evaluation of the jaw and careful provoking of the pain. This can be with light touch, cold or hot or heavier touch. The doctor may also perform some simple neurological tests.

After this, the doctor may decide he or she wants to order some diagnostic tests, which could include magnetic resonance imaging (MRI), computer assisted tomography (CT) or other x-rays or films. In addition the doctor may want to order blood tests, urinalysis and other tests. These tests are used to make sure that there is nothing else wrong that may be masquerading as a neuropathic pain.

To figure out if the pain is peripheral or central (or both), the doctor may use a series of diagnostic injections, usually with a local anesthetic, similar to what you might get when you have a tooth filled. By "numbing" the nerves in the peripheral part of the nervous system and seeing its effect on the pain, the doctor can gather important information that may help in planning a more effective treatment. A battery of psychological tests may be appropriate since anxiety and depression can be closely related to persistent pain.

Depending on the complexity of the problem, the orofacial pain specialist will decide which of the diagnostic tests are appropriate for your problem. After piecing together the results of the history, examination and diagnostic tests, the doctor will make a diagnosis and recommend a treatment strategy. Sometimes treatment is done on a trial basis and several treatments may be attempted before an effective approach is found. In addition, your doctor may enlist the help of several professionals to provide what is called a "multidisciplinary approach."

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Common Neuropathic Pain Disorders and their Treatment

Trigeminal Neuralgia
Of the neuropathic pain disorders, perhaps the best known in the head and neck is trigeminal neuralgia (TN). It often appears suddenly as a sharp shooting lightning-like pain lasting a few seconds. There is usually a specific trigger area that causes the pain to occur when touched. Patients are often unable to shave, comb their hair or touch their face for fear of triggering the pain. Sometimes the pain is triggered by slight movement of the affected part of the face. The disorder is more common after age 50 but can occur at any age.

The trigeminal nerve is the main nerve that provides sensation to the face. The nerve is divided into three branches on either side of the face and the pain of TN usually follows one or more of these branches. The cause of TN is often unknown, but many doctors and researchers believe that some patients may have a compression of the trigeminal nerve by an artery or vein. Also, patients with tumors in the brain and others with multiple sclerosis may suffer from TN-like pain. Therefore, all patients need to be carefully evaluated before starting therapy. There are also several other less common neuralgias involving other nerves of the face.

The first line of treatment for TN is usually with one of a group of medications called "anticonvulsants." Often patients begin a very low dose and built up to the lowest effective dose. It can take as long as eight weeks before you and your doctor can determine if a particular drug is effective. Some of these medications require periodic monitoring of the blood to avoid unwanted side effects. There are several different medications available so that if the first one your doctor chooses isn't as effective as you or the doctor would like or if you can't tolerate the side effects, other medications can be tried.

When medications are not effective in relieving your pain, surgery or special injections or "blocks" may be recommended. Surgery generally is performed by a neurosurgeon while blocks generally are done by specially trained anesthesiologists. The injections are aimed at temporarily or permanently blocking the effected branch of the trigeminal nerve. An electronic procedure called "radiofrequency lesioning" and a freezing procedure called "cryosurgery" may be recommended. . Patients should exercise caution before undergoing these procedures because permanent numbness and continued pain occasionally results. The most common procedure involving radiation is called a gamma knife procedure, and has shown good success in many patients, without the adverse effects of some of the other procedures mentioned above.

There is also a surgical procedure available known as the "Janetta procedure", designed to take the pressure off the trigeminal nerve by placing a small cushion between it and a blood vessel. If the neuralgia-like pain is caused by pressure from a tumor, the patient will likely be treated by surgery, radiation therapy and/or other forms of treatment appropriate for the particular kind of pathology.

As with treatment for any disorder, the patient should have a frank discussion of the risks and benefits of the chosen treatment as well as treatment alternatives. There is never anything wrong with getting a second opinion.

Pre-Trigeminal Neuralgia
Some patients will experience a vague, deep dull achy pain in the face or teeth. It may be constant or on and off. Local pain relievers (anesthetics) often temporarily relieve the pain. This pain eventually develops into TN and so is called "pre-trigeminal neuralgia." This is treated with the same medications as TN. This pain can be difficult to diagnose but becomes evident as it presents itself in the classic form of trigeminal neuralgia.

Atypical Odontalgia (Phantom Tooth Pain)
As discussed at the beginning of this section, some patients develop persistent tooth pain and go from dentist to dentist only to be told there is nothing wrong with their teeth. This pain often follows a dental procedure such as a root canal or filling. Unfortunately many patients wind up undergoing unnecessary root canal treatment, gum surgery and even extraction in an attempt to treat their pain. The pain actually starts at the peripheral nerves that go to the teeth and, in some cases, progresses to changes in the central part of the nervous system that senses pain in the teeth.

When the pain comes from the part of the nerve close to the teeth or gums where the pain is felt, injections of local anesthetics and steroids may be effective. Some patients find relief by applying specially prepared creams with various combinations of medications mixed in them. In patients where the pain is central, medication taken by mouth may be needed on a daily basis. These often include antidepressants and anticonvulsants and in some cases opioids.

To locate knowledgeable and experienced specialists in orofacial pain, contact:
The Academy of Orofacial Pain (AAOP)
19 Mantua Road
Mount Royal, New Jersey 08061
(609) 423-3629
www.aaop.org

This information was produced by the American Academy of Orofacial Pain (www.aaop.org). Adapted and printed with permission of the American Academy of Orofacial Pain.

The American Academy of Orofacial Pain is an organization of health care professionals dedicated to alleviating pain and suffering through the promotion of excellence in education, research and patient care in the field of orofacial pain and associated disorders.

This section is intended to provide general information on orofacial pain and is not a substitute for careful evaluation by a physician or orofacial pain specialist.

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