The Puzzle of Burning Mouth Syndrome
words by merry sue baum / photograph by pete byron
Eli Eliav, DDS, director of the division of orofacial pain, UMDNJ-New Jersey Dental School
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irginia Mencor is sure she has a guardian angel. The 85-year-old has been healthy all of her life and says she has never taken medication for any reason. Ever. She is, indeed, a rare breed. Her luck eventually changed, but the Elizabeth, NJ, resident still feels very fortunate.
Not long ago, she began experiencing a burning sensation in her mouth, especially on her tongue. She’d had all of her dental work done at NJDS, so she returned to the school in hopes of solving the problem. “I would be fine when I woke up in the morning, but as soon as I ate, my tongue would begin to burn,” she says. “It got worse as the day went on. The next day, it would happen all over again.”
Mencor has a disorder known as burning mouth syndrome, or BMS. Characterized by a burning sensation in the oral cavity (lips, tongue and/or gums) that is not caused by any local or systemic disorders, it is most often seen in peri- and postmenopausal women. “Burning in the mouth can be caused by vitamin or iron deficiencies, anemia, allergies, certain medications or diabetes,” explains Eli Eliav, DDS, director of NJDS’s Division of Orofacial Pain. “We determined that Ms. Mencor did not have any of those conditions, but she did have the classic symptoms of BMS: the sensation was triggered by eating and continued to get worse throughout the day.”
At the time that Mencor went to the Orofacial Pain Clinic, the researchers were conducting studies in their lab using Quantitative Sensory Testing (QST), a computer testing system that employs thermal, mechanical and electrical stimuli to determine pain levels and diagnose neuropathic pain. (The stimuli are applied on the face and are completely painless.) Using QST, the NJDS researchers were the first to demonstrate that BMS is caused by reduced activity of one of the main sensory nerves in the tongue. There are two: the chorda tympani, which supplies taste, and the lingual, which supplies heat, cold, pain and pressure. The two nerves continually balance each other—a common sensory behavior in the human body. In BMS, however, the chorda tympani nerve becomes less active and the lingual nerve is basically unleashed and becomes overactive. “We found this in about 85 percent of our BMS patients,” says Eliav.
Because the condition occurs most frequently in women going into or experiencing menopause, many seek help from their gynecologists. Often the diagnosis is depression or anxiety and antidepressants are prescribed. These types of drugs have a secondary effect on neuropathic pain, so they sometimes help quell the burning sensation. “We now know that BMS is not the result of menopausal depression but rather a neuropathic pain disorder,” says Eliav. “We also know it does not result from having a dental procedure performed, as many people think.”
There are systemic medications that help restore the balance between the two nerves. One is the antiepileptic drug, clonazepam, which Mencor now takes in small doses. “I don’t like taking medication every day, since I never did. But it is helping me,” she says. “I’d be very willing to participate in another study, especially if they could find a cure that didn’t include taking pills.”
Eliav’s lab is working on exactly that. Since the researchers now understand the pain mechanism involved in BMS, they are looking for innovative treatments, especially for those without guardian angels. n