Original Article Could methylene blue be used to manage burning mouth syndrome? A pilot case series Papa Abdou Lecor 1 , Babacar Touré 1 , Nathan Moreau 2,3 , Adeline Braud 3,4 , Wisam Dieb 3,5 , Yves Boucher 3,5,* 1 Service de Physiologie, Département d’Odontologie, Université Cheikh Anta Diop, Dakar, Senegal 2 Service de Médecine Bucco-Dentaire, Hôpital Bretonneau Paris, AP-HP, France 3 Université de Paris, LabNOF (EA 7543), 75006 Paris, France 4 Service d’Odontologie, Hôpital Rothschild, AP-HP, Paris, France 5 Service d’Odontologie, Groupe hospitalier Pitié-Salpêtrière, AP-HP, Paris, France (Received: 26 September 2019, accepted: 12 January 2020) Keywords: Trigeminal pain / orofacial nociception / neuropathy / glossodynia / stomatodynia / methylthioninium chloride Abstract - - Objective: Burning mouth syndrome is a disabling condition of complex pathophysiology characterized by spontaneous pain felt in the oral mucosa in the absence of evident mucosal lesions which lacks efficient treatments to this day. The purpose of this study was to demonstrate the efficacy of methylene blue in the management of burning mouth syndrome. Methods: The study was conducted at the dental clinic of the Anta Diop University and Newtown dental clinic of Dakar, Senegal. A solution of methylene blue as a mouth-rinse (0.5%) was applied for 5 minutes in five patients satisfying the ICHD-3 diagnostic criteria for burning mouth syndrome. This procedure was repeated every 6 hours 3 times per 24h, during 7 days. Using numeric rating scale, pain severity was assessed as the mean pain felt during the last day of application. Results: After 7 days, the pain was significantly reduced by two-thirds and almost absent at 3 and 6 months follow-up. No secondary effects of the use of methylene blue were observed. Putative mechanisms of action and potential implications for treatment are discussed. Conclusion: Methylene blue is an old compound but a novel topical therapy that could prove beneficial in the management of burning mouth syndrome. Introduction Burning mouth syndrome (BMS) is a disabling condition characterized by spontaneous pain felt in the oral mucosa, defined by the International Headache Society (IHS) [1] as “intraoral burning or dysesthetic sensation, which occurs daily for more than 2 hours and persists for more than 3 months, without clinically obvious causal lesions” (ICHD-3) [1]. As opposed to secondary BMS which has a causal factor [2], primary or idiopathic BMS is of unknown etiology. The prevalence of BMS affects between 0.01% and 3.7% in the adult population but can be much higher in specific patient groups such as menopausal women (12–40%); the average sex- ratio is approximately 1 man for 7 women, depending on the studies [3,4]. The characteristics of BMS have been comprehensively reviewed with focus on its historical [5,6], clinical [2,7], and pathophysiologic [8–12] characteristics. Accumulating evi- dence suggest that BMS is a neuropathic condition experienced by patients presenting morphological and functional alter- ations in both the peripheral and central nervous system, detectable at the subclinical level. Although often described as a clinically homogenous entity, BMS might refer to different conditions [9,13–15]. Regarding BMS therapy, several comprehensive reviews and meta-analysis [2,16–23] overall indicate both a lack of satisfactory treatments and a poor level of evidence of the existing studies with few randomized controlled trials (RCTs). Considering the disabling nature of BMS, including alterations of quality of life and social integration [13,24,25], high levels of somatic and psychiatric/psychological comorbidities [26–31], the need for efficient treatment is crucial for patients and a public health issue. To address such an issue, the 2016 Cochrane review [20] suggests designing well controlled RCTs and identifying new therapeutic approaches. Methylene Blue (MB) In Senegal, some patients spontaneously use Methylene Blue (MB) to alleviate oral pain, although no recommendation for this indication can be found in the literature. MB is a * Correspondence: yves.boucher@univ-paris-diderot.fr J Oral Med Oral Surg 2020;26:35 © The authors, 2020 https://doi.org/10.1051/mbcb/2020032 https://www.jomos.org This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1