Optimized diagnostic criteria for burning mouth syndrome should remain clinically grounded

Dear Editor,

We read with great interest the prospective field test by El-Rubaiy et al. of the ICHD-3, ICD-11, ICOP-1, and WCOM criteria for burning mouth syndrome (BMS) and their proposal for optimized ICOP criteria with improved diagnostic performance. ¹ We commend this important contribution. However, a data-driven optimization strategy, if not integrated with the broader clinical literature and conceptual developments, may unintentionally narrow the clinical construct of BMS and reduce the criteria's applicability in routine practice.

Our group has contributed to the debate over how BMS should be defined in future ICHD and ICOP revisions, including by advocating a broader diagnostic perspective and exchanging views on oral dysaesthetic and perceptual disorder, oral cenesthopathy, and the need to preserve meaningful diagnostic distinctions.^2–5 This dialogue raises a central question: should future diagnostic systems primarily maximize statistical discrimination, or should they also preserve the clinical heterogeneity of patients encountered in practice?

The study by El-Rubaiy et al. addresses this issue. However, the optimized ICOP criteria introduce two restrictive elements: mandatory bilateral symptoms and symptoms lasting at least six hours per day. ¹ Although these characteristics improved diagnostic performance within the study cohort, they may reflect characteristics of that cohort rather than universal features of BMS. Diagnostic criteria should capture the clinical spectrum, not only the most prevalent presentation in a single study population.

This concern is not merely theoretical. In a retrospective cohort of 834 patients with BMS, 239 individuals (28.7%) had symptoms confined to one side. ⁶ Making bilaterality obligatory would narrow the diagnostic construct rather than refine it. Although a bilateral presentation is common, requiring it may exclude patients who otherwise fit the broader clinical picture of BMS.

Similarly, the six-hour requirement raises concerns about clinical applicability. Patients rarely describe symptoms using precise hourly thresholds. In oral medicine practice, they more commonly report that symptoms are present for most of the day and fluctuate in intensity. It remains unclear whether the six-hour threshold reflects a biologically meaningful distinction or merely the characteristics of the derivation cohort.

A further concern relates to the multidimensional nature of BMS. Evidence supports the view that BMS extends beyond burning pain alone. Patients often report associated sensory manifestations, including xerostomia, dysgeusia, globus sensation, foreign-body sensation, altered salivary perception, and other dysaesthetic symptoms. ⁷ In a cohort of 500 patients with BMS, xerostomia was reported by 61.6%, dysgeusia by 45.0%, globus sensation by 36.6%, and foreign-body sensation by 78.8%. ⁷ These observations suggest that BMS may be better conceptualized as a multidimensional oral sensory disorder than as a narrowly defined bilateral burning pain condition.^6,7

This issue is particularly relevant to patients who describe their symptoms as stinging, tingling, painful dryness, a foreign-body sensation, oral discomfort, or dysaesthetic pain rather than exclusively as burning.^5,6 Restrictive symptom-based criteria may exclude such patients from the BMS framework despite overlap in clinical presentation, psychosocial burden, and therapeutic needs. ⁶ Diagnostic criteria should avoid overemphasizing a single symptom dimension at the expense of the broader phenotype.

At the same time, as emphasized in this exchange, excessively broad criteria may blur distinctions among BMS, oral mucosal pain with identifiable causes, oral dysaesthetic and perceptual disorder, and oral cenesthopathy.^2–5 The challenge is not simply to maximize sensitivity and specificity but to preserve meaningful diagnostic boundaries. This is important because BMS is increasingly discussed as a complex orofacial pain condition involving peripheral, central, sensory, and psychosocial mechanisms.

Emerging therapeutic observations also reinforce the value of preserving clinically meaningful phenotypes. A recent case report described complete resolution of BMS symptoms in a patient with chronic migraine after initiation of galcanezumab, a humanized IgG4 monoclonal antibody that binds to calcitonin gene-related peptide (CGRP); the BMS symptoms temporarily recurred when dosing was delayed. ⁸ Although a single case cannot establish efficacy, this observation suggests a possible migraine–BMS mechanistic link and highlights CGRP-targeted therapy as a potential avenue for further investigation.

Another consideration is that the optimized criteria were derived from 34 patients diagnosed with BMS. ¹ Although such data are valuable, characteristics observed within a specific cohort should not be incorporated into universal diagnostic rules without external validation in larger and geographically diverse populations.

We believe that future revisions of ICOP and ICHD should integrate three complementary forms of evidence: field-testing studies; clinical experience accumulated through decades of research and patient care; and literature on oral dysaesthetic and perceptual presentations and the multidimensional sensory phenotype of BMS.^2–7 Rather than making bilaterality and a fixed daily duration mandatory, future criteria might treat these features as supportive or specifier-level characteristics.

El-Rubaiy et al. have provided valuable data and made an important contribution to the refinement of BMS diagnostic criteria. Our concern is that these findings should serve as a starting point for broader international consensus-building rather than as a stand-alone basis for redefining BMS. Diagnostic criteria should not only maximize statistical discrimination but also capture clinical reality. Future revisions should balance diagnostic accuracy with clinical inclusiveness, ensuring that patients with genuine BMS are not excluded by fixed thresholds for laterality, daily duration, or verbal symptom descriptors.