WASHINGTON — “Burning mouth syndrome,” a constellation of symptoms involving burning sensations of the tongue, palate, lips, and buccal mucosa, responds to transcranial magnetic stimulation and drugs that increase levels of γ-aminobutyric acid, Robert I. Henkin, M.D., said at the Clinical Research 2005 meeting.
The neurologic condition, which occurs late in adulthood, is most common among postmenopausal women. The specific exact etiology remains unknown.
Many primary care physicians are unfamiliar with the phenomenon of burning mouth syndrome, and tell patients that they are imagining things, or that they are simply anxious, said Dr. Henkin, director of the Taste and Smell Clinic, in Washington.
The study included 53 patients with burning mouth syndrome, 42 women and 11 men, aged 20–84 years. Dr. Henkin and radiologist Lucien Levy, M.D., of the George Washington University Medical Center, used magnetic resonance spectroscopy (MRS), specifically, a standard 2-dimensional J-point resolved excitation in the steady state (J-PRESS) sequence, to measure levels of γ-aminobutyric acid (GABA), glutamic acid, N-acetylaspartate, choline, and creatine in various regions of patients' brains.
Prior to treatment, patients with burning mouth syndrome had significantly lower levels of GABA compared with healthy volunteer controls who were age- and sex-matched to the patients, Dr. Henkin said at the meeting, which was sponsored by the American Federation for Medical Research.
Treatment with transcranial magnetic stimulation (TCMS) increased the GABA concentrations in the brain and relieved the burning sensations in 31 (68%) of the 46 treated patients. Their response suggests that the etiology of burning mouth syndrome lies in changes in a specific inhibitory neurotransmitter in the central nervous system.
For the TCMS treatment, the patients, acting as their own controls, received TCMS on each shoulder and the neck at levels of 0.2–0.4 Tesla (T), the unit used to measure magnetic field intensity prior to the application of TCMS to the head at the level of 1.1 T. The patients reported no changes in their burning mouth sensations at 0.2–0.4 T, but 31 of the 46 patients who received magnetic stimulation to the head at a level of 1.1 T reported improvement in the burning sensations.
The magnetic treatment had no apparent side effects, no associated pain, and relieved the burning feeling in a matter of hours or days, Dr. Henkin said in an interview. The main drawback is that some patients required more than one or two additional magnetic stimulation treatments to completely alleviate their burning symptoms.
The results of the study provide measurable evidence that brain GABA levels mirror patients' pain levels, going up or down with brain GABA levels as shown in the images of MR spectroscopy of brain neurotransmitters, which show a 2-dimensional spectrum of the inhibitory neurotransmitter GABA.
Pharmacologic treatment with GABA-ergic drugs may be helpful to patients who don't respond to magnetic stimulation. The dose and length of treatment with GABA-ergic drugs to lessen the pain of burning mouth vary widely among patients, said Dr. Henkin, reporting on his experience.
The results may be complicated by side effects. For a drug such as haloperidol, for example, doses may vary from 0.5 to 1.5 mg daily and patients may need to take them for 4–10 weeks to obtain an effect. In addition, patients often need a maintenance dose, which might range from 0.25 to 0.5 mg. By contrast, most patients treated with TCMS find long-term relief after a few sessions and approximately 20% experience relief within a week of a single treatment, Dr. Henkin said.
The patients in the poster study who did not respond to TCMS have been treated with GABA-ergic drugs, but this treatment is ongoing and the results have yet to be analyzed, Dr. Henkin said.
Drug therapy for burning mouth syndrome requires careful supervision and time, compared with the simple, rapid, and direct improvements associated with TCMS, he noted.
Dentists or primary care physicians are often at a loss as to how to treat patients' “dragon breath,” and burning sensations in the oral cavity, since there is no anatomic change in the tissue. When a patient presents with such complaints, consider a neurologic referral and an evaluation for GABA-related treatments.
For more information about the diagnosis and treatment of burning mouth syndrome and other taste and smell disorders, visit www.tasteandsmell.com
Dr. Robert I. Henkin and associates used MR spectroscopy to measure levels of the inhibitory neurotransmitter GABA. This image shows an example of pure GABA in a solution. Courtesy Dr. Lucien Levy