NEUROPATHIC OROFACIAL PAIN
Neuropathic pain disorders arise from disorder or injury to the nervous system. Neuropathic Orofacial Pain disorders are often chronic and arise from the nerves affecting the head, face and mouth.
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 such outlying areas of the body as the arms, legs, trunk, face and teeth. The peripheral nerves have special receptors which when stimulated by pressure, heat, chemicals or pain, begin firing electrical impulses back along the nerve. The nerves course their way into the spinal cord where they connect to a second nerve which extends up the spinal cord to the brain where the information is processed. In the brain, a different nerve continues to carry the message to other parts of the brain where the message is actually interpreted. The brain has many complex chemical mechanisms to either increase or decrease the pain-related information streaming into it.
If a peripheral nerve is injured, for example a tooth has a nerve injury from decay and subsequent root canal treatment, one 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, the tooth may be extracted and can 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 further up the chain of nerves into the brain. These changes can result in continued pain, despite normal healing in the area of the tooth. Research has also 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 called "plasticity" which means that the nervous system can be altered so that non-painful signals such as touch and pressure are interpreted by the brain to be painful. The brain then continues to perceive that the area that was first injured is the area that is painful even though it has healed.
Neuropathic Orofacial Pain may have several qualities that distinguish them from other pains. Neuropathic pain can vary from a general constant nagging dull ache to a sharp, stabbing, electric shock-like pain in the area supplied by the injured nerve. People with Neuropathic pain often describe pain as burning, prickling, or electrical. The pain may just happens by itself, or normally non painful light touch, or hot or cold stimulation can trigger attacks. Sometimes it is difficult 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 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 it. Sometimes it is difficult 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".
TREATMENT OF NEUROPATHIC PAIN
Patients with neuropathic orofacial pain often visit many doctors and undergo many tests, all of which are negative.
Even more frustrating and upsetting to the patients is that they undergo useless treatments. In the mouth, this may include gum surgery, root canal and even extraction, which often results in only temporary relief, no relief at all, or in many cases an increase in pain.
Establishing a diagnosis is the first step to successful treatment. Orofacial pain specialists such as Dr Delcanho perform a comprehensive evaluation, which may include a thorough history, examination, and diagnostics tests. The examination may consist of touching different areas of the head, neck and inside the mouth, measurements and evaluation of the jaw, head and neck, and gentle provoking of the pain. This can be with light touch, cold or heat or heavier touch. Diagnostic tests could include magnetic resonance imaging (MRI), computer assisted tomography (CT) or other radiographs (X-rays). Blood tests, urinalysis, and other tests are used to make sure that there are no other factors that may be contributing to the neuropathic pain. Sometimes diagnostic injections, usually with a local anesthetic, are used to "numb" the nerves in the peripheral part of the nervous system and determine its effect on the pain. Sometimes referral to a psychologist may be appropriate since anxiety and depression often accompany persistent pain.
Depending on the complexity of the problem, Dr Delcanho will decide which of the diagnostic tests are
appropriate. 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, sometimes the other specialists will be enlisted - the "multidisciplinary approach.
Fortunately for those suffering from orofacial neuropathic pain, while much is unknown about causes, a number of treatments have been found effective. A combination of treatments and therapies is often found most effective in managing orofacial neuropathic pain symptoms. Dr Delcanho will discuss with you the appropriate treatment plan for orofacial disorders discussed here.
Of the neuropathic pain disorders, perhaps the best known is Trigeminal Neuralgia (TN). It often appears suddenly as a
sharp, shooting, lightning-like pain lasting a few seconds. There may be a specific trigger area that, when touched, causes the pain to occur. 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 feel that at least in some patients, there may be a compression of the trigeminal nerve by an artery or vein within the brain. Also, patients with tumors in the brain and 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.
Anti-seizure medications: The first line of treatment for TN is usually with one of a group of medications called "anti-seizure medications". Medicines that block nerve firing are typically the first line of treatment for trigeminal neuralgia. A doctor may prescribe anticonvulsant drugs including carbamazepine, oxcarbazepine, clonazepam, topiramate and a number of other medications found effective in decreasing nerve overactivity. Proper dosing of these potent medications is often identified by prescribing gradually increasing amounts of the drug and carefully monitoring effects and side effects.
Tricyclic antidepressants: If pain manifests as constant, burning or aching, tricyclic antidepressants have been found useful in pain management.
When medication is ineffective, surgery or special injections (blocks) may be recommended. Surgery is generally performed by a neurosurgeon while blocks are performed by specially trained anesthesiologists. The injections are aimed at temporarily or permanently blocking the effected branch of the trigeminal nerve. Patients should exercise caution before undergoing these procedures because permanent numbness and continued pain can occur.
Rhizotomy procedures: Rhizotomy procedures block pain by destroying select nerve fibers. The end result can cause numbness in the face. In the treatment of trigeminal neuralgia, several forms of rhizotomy have been used effectively. Balloon compression blocks pain signals by inflating a balloon next to the trigeminal nerve at the base of the skull with enough pressure to damage the nerve. Radiofrequency lesioning uses electrical currents to identify the portion of the trigeminal nerve responsible for pain and destroys those nerve fibers with a heated electrode. In stereotactic radiosurgery, highly focused beams of radiation directed at the trigeminal nerve at the base of the skull slowly cause a lesion on the nerve over a period of several months.
Microvascular decompression: This surgical procedure works by implanting a cushion between the trigeminal nerve and the compressing blood vessel.
Atypical Odontalgia (Persistent Dento-Alveolar pain)
As previously mentioned, 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, but not always, follows a dental procedure such as a root canal or filling.
Unfortunately, many patients undergo unnecessary root canal treatment, gum surgery, and even extraction in a vain attempt
to treat their pain. The pain actually starts at the peripheral nerves that go to the teeth and in some cases can progress to changes in the central part of the nervous system that then senses tooth pain. When the pain comes from the part of the nerve close to the teeth or gums, 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 rather than peripheral, medication taken by mouth may be needed on a daily basis. These often include
antidepressants and antiseizure medications and in some cases even narcotics.
Local anesthetics and steroid injections may reduce pain symptoms if pain originates in a nerve near the teeth or gums. The application of prepared medicinal creams has also been found to provide pain relief. Drug treatment options include antiseizure medications, tricyclic antidepressants or narcotics.
Trigeminal Nerve Injury
The trigeminal nerve is the large sensory nerve that supplies feeling to your face, mouth, eyes, nose and scalp.
Nerve injury can sometimes result from dental treatments such as dental injections, root canals treatments, insertion of dental implants, removal of teeth, and other surgical treatments. These dental injuries affect the trigeminal nerve, usually involving the lower lip and/or tongue areas causing a mixture of pain, numbness and strange sensations that may be present all the time or intermittently.
Trigeminal nerve injuries can be extremely distressing. Although the majority of patients regain normal sensation and function within a few weeks or months, some are left with abnormal sensation or pain, which can cause major problems with speech and chewing as well as adversely affecting well-being.
Trigeminal nerve injuries can cause episodes of intense, stabbing, electric shock-like pain in the areas of the face where the branches of the trigeminal nerve are distributed: the lips, eyes, nose, scalp, forehead, upper jaw and lower jaw. Sometimes you may notice pain with touch or when a cold breeze hits your face. Eating, speaking, drinking, brushing your teeth, shaving or applying makeup may all be difficult because of the changes in feeling.
If pain from nerve damage sustained during a dental procedure does not improve within 6 to 8 weeks, surgical repair can be considered. The rate of success in repairing injuries to nerves sustained by trauma from dental and medical procedures improves the closer they are performed to the incident. After 8 weeks the chance of success is markedly reduced, and in fact surgery may only serve to worsen the pain!
Furher informaton on nerve injury can be obtained at: http://trigeminalnerve.org.uk/