Central mechanisms in burning mouth syndrome involving the olfactory nerve: a preliminary study

Burning mouth syndrome (BMS) is characterized by a continuous sensation of burning or heat in the oral cavity, mainly on the tongue, palate and/or gingiva 1–3, in the absence of a primary cause 4–5. Systemic diseases, such as diabetes mellitus or anemia, must be ruled out 3. It is most common among postmenopausal women and causes intense discomfort and suffering. There is no defined etiology for BMS other than precipitating causative factors, and it is still considered idiopathic. One of the most widely accepted theories is that the partial or total loss of chorda tympani (facial) nerve function disinhibits the trigeminal nerve, resulting in pain along trigeminal pathways, as both taste and pain systems are regulated by interneurons of the central nervous system (CNS) 6–8. This theory is based on evidence of neuropathic mechanisms 9–10, including the loss of small fibers in oral tissues 11, salivary and somatosensory abnormalities , reduced corneal reflexes 15, and peripheral nerve degeneration 11–16. Despite the known interaction between smell and taste 17, we found no studies that investigated it in relation to BMS. Thus, the objective of this preliminary study was to determine tactile, pain, thermal, gustative and olfactory thresholds in a group of patients with BMS as compared with controls.