Patient presentation

A 64-year-old Caucasian female hairdresser, who had been divorced for several years, had a 10-year history of a burning sensation in her tongue and lower lip. This burning pain had started spontaneously. The only possible event that she could remember was accidentally sucking her lower lip with food before the BMS pain started. At the same time, she experienced a metallic taste and mouth dryness. At first, she went to her family physician and was examined by screening laboratory tests. All blood tests including haemoglobin level, platelet count, white blood cell count, red blood cell count, blood urea nitrogen, creatinine, glucose, albumin, total protein, total bilirubin, liver function (alanine transaminase, aspartate transaminase), thyroid function (thyroxine, thyroid-stimulating hormone), electrolytes (Na ⁺ , Cl ⁻ , HCO ₃ ⁻ , Ca ⁺⁺ ), serum ferritin levels, cholesterol, and triglycerides were within the normal limits. She underwent an X-ray examination and a biopsy of her lower lip submucosal and salivary glands in a dental clinic, but there were no abnormal findings. Although opioids, antibiotics, and topical dexamethasone were administered, the burning sensation did not ameliorate. Six months after the burning sensation had started, the patient attended a pain clinic. To treat the chronic pain, several antidepressants, including a tricyclic antidepressant (TCA), serotonin and norepinephrine reuptake inhibitor (SNRI), and selective serotonin reuptake inhibitor (SSRI), were prescribed. However the TCA was discontinued due to drowsiness and the SNRI and SSRI were discontinued due to nausea. The patient found these side effects intolerable, hence these medications were continued for only 2 or 3 days. Gabapentin was also prescribed for a month, but there was no effect on the BMS pain. Alpha-lipoic acid was not prescribed because the patient refused to take medication at that time. After these medications, the patient did not have any treatment for over 8 years.

The patient attended the laboratory alone for possible treatment with TMS. At this first examination she was fully oriented and verbally fluent. She had no history of any psychiatric conditions. Another oral examination failed to find any cause of the BMS. The continuous pain developed as the day progressed and improved with meals. Based on clinical, laboratory, and historical data, a diagnosis of BMS was established. She had a history of migraine and menopausal syndrome and had taken medications for over 5 years (sumatriptan 10 mg/day, rizatriptan 10 mg/day, clonazepam 1 mg/day, progesterone 125 mg/day). These medications were not changed during this clinical study.

After explaining the potential risks of the treatment and with her consent, rTMS was started with 10 Hz to the left DLPFC at medial frontal 10–20 system EEG-electrode location (F3), as defined by Beam et al. The intensity was set at 110% of the resting motor threshold (RMT), 5 s on and 10 s off for 15 min (3000 pulses/day) for 10 consecutive weekdays. A MagVenture MagPro ×100 Stimulator (MagVenture, Inc., Denmark) with figure-of-eight coil was used for the RMT assessment and all rTMS sessions. For the RMT assessment, the TMS machine was initially set to 50% of its maximal output. Single pulses were administered near the primary motor cortex until the area that produces contraction of the abductor pollicis brevis (APB) was identified. The minimum machine output necessary for visible APB contraction 50% of the time that pulses were delivered was used to determine RMT.

A visual analogue scale (VAS) for tongue pain intensity was used as the primary outcome measure. We also recorded a VAS for the head pain under the TMS coil during each session and applied the Brief Pain Inventory (BPI) functional impairment, Short Form McGill Pain Questionnaire (SFMPQ), Patients’ Global Impression of Change (PGIC), and Clinical Global Impression Global Improvement (CGI-I).