Stress, not joint, may be source of TMJ disorders.
In the past, therapy has focused on the jaw joint itself. Invasive procedures to "fix" the joint have had disastrous results, including the Proplast (Vitek) implants used in the 1970s and 1980s. The implants broke down under constant jaw pressure, causing immune reactions, loss of jaw bone, and even penetrations of the cranial vault.
But in many cases, especially early in the disorder, the joint shows no degenerative changes. That fact, coupled with temporomandibular joint (TMJ) disorder's high comorbidity with functional pain syndromes, has researchers looking beyond the jaw joint for the cause, said Capt. John Johnson, DC, USN, residency director of the Orofacial Pain Program, National Naval Dental Center, Bethesda, Md.
More than 10 million Americans experience TMJ disorders each year. These poorly understood conditions are characterized by pain in the jaw and associated muscles. The pain can be severe, limiting normal jaw movement and inhibiting the ability to speak, eat, and swallow.
Patients with TMJ disorder "are significantly more likely than controls to report other disorders, including functional pain disorders such as fibromyalgia, irritable bowel syndrome, and noncardiac chest pain," Dr. Johnson said.
In a study he is preparing for publication, Dr. Johnson examined rates of 13 comorbid disorders including panic attack and functional pain disorders in patients referred to the orofacial clinic for TMJ disorder. Such patients had an average of 4.5 comorbid conditions, while patients coming for a routine dental exam had only one.
TMJ disorder patients also are significantly more likely than controls to report negative early life experiences. An anonymous survey of such patients at the University of Kentucky, Lexington, orofacial pain center found that up to 70% of patients reported early neglect or abuse (J. Orofac. Pain 9: 340-46, 1995).
Of those who seek medical treatment, 90% are women in their childbearing years. Research suggests that TMJ and functional pain disorders may be related to a heightened female response to stress that manifests in peripheral symptoms--in the case of TMJ disorder, jaw clenching, or tightening.
Some functional MRI studies suggest that the amygdala reacts to stress differently in men and women. In men asked to recall an emotionally charged film clip, the amygdala activated striatal and cortical brain areas, indicating a cognitive response to the memory. In women, the amygdala activated hypothalamic and brain stem regions (Neurobiol. Learn. Mem. 75:1-9, 2001).
"This kind of a response can lead to peripheral physical reactions, including things like jaw clenching," Dr. Johnson said. "If this stress response is prolonged, it can result in pain and even physical changes in the joint."
The stress-reaction theory makes even more sense when seen in the context of the epidemiology of TMJ disorder, Dr. Johnson said. The peak onset is in the stressful mid-20s and 30s, "when we are pushing harder, trying to figure out who we are and where we are going in life." Once people begin to experience a more settled and stable life, the incidence of TMJ disorder drops sharply.
Headache and pain in the face, jaw joint, and ear or surrounding tissues are the primary symptoms of TMJ disorder. Pain in the posterior molars may be present; sometimes it migrates from one side of the mouth to the other. Patients also may say that their jaw locks when open or closed. There may be a limited ability to open the mouth comfortably, he said. "The patient may tell you the bite feels uncomfortable, 'off,' or is changing somehow." Popping or clicking sounds in the jaw joint are no longer considered a diagnostic hallmark.
It's important to rule out other possible causes of jaw pain, including otitis media and tooth abscess. The initial work-up should include a cranial and cervical nerve screen, assessment of mandibular range of motion, and a dental exam. Imaging studies are not very helpful in early stages of TMJ disorder because there are usually no physical changes.
Once peripheral causes have been excluded, it's time to focus on stress and any comorbid conditions. "It's very important not to just say, 'OK this is just a TMJ complaint,'" Dr. Johnson said. "Look for what else is going on, such as irritable bowel syndrome or panic attacks."
A sleep assessment is important too because poor sleep is associated with stress and bruxism, both of which contribute to jaw pain.
Sometimes medication may be a culprit. Patients who are taking selective serotonin reuptake inhibitors may experience sleep problems accompanied by bruxism or jaw clenching, especially if the dose has recently been increased, so it's important to ask about that as well.
BY MICHELE G. SULLIVAN
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|Title Annotation:||Neurology; Temporomandibular joint|
|Author:||Sullivan, Michele G.|
|Publication:||Internal Medicine News|
|Date:||Oct 15, 2004|
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