Relieving pain with OnabotulinumtoxinA in refractory burning mouth syndrome: protocol and outcomes of an exploratory case series.

backgroundBurning mouth syndrome (BMS) is a chronic orofacial neuropathic pain disorder, occurring in the absence of clinically evident mucosal lesions or identifiable oral pathology that can explain the symptoms. A significant proportion of patients experience uncontrolled symptoms despite multiple therapies. OnabotulinumtoxinA (onaBoNT/A) is used in neuropathic pain, as clinical trials have shown benefits in peripheral and central neuropathic pain management with its application. We present an exploratory case series of four patients with refractory BMS treated with intradermal onaBoNT/A injections.

methodsFour patients with refractory BMS were included in this study. OnaBoNT/A intradermal injections were performed in the inner labial mucosae and tip of the tongue. We assessed pain intensity before the procedure and after 15 days, adverse effects, time to symptom recurrence, cumulative effects with multiple procedures, and patients' global impression of change.

resultsAll patients reported the procedure was quick and well tolerated. No immediate adverse effects were identified. All patients had significant pain reduction at 15-day follow-up assessment. Regarding adverse effects, one patient reported transient lower lip asymmetry in one procedure, and another reported transient mild mouth closure impairment. Symptoms recurred between 2.5 and 3.0 months after the first procedure. Three patients desired to continue the treatment. One patient reported no symptom recurrence after four procedures with three-month intervals; after four procedures, the treatments were suspended, and she remained asymptomatic until the end of follow-up. One patient reported incremental benefit from repeated procedures. All patients reported the treatment had a meaningful impact on their daily life.

conclusionsOur results suggest that intradermal onaBoNT/A injections may constitute an effective and durable treatment option for patients with BMS refractory to conventional therapies. Despite these favourable outcomes, adverse events were noted in procedures targeting the labial mucosa. In future applications, we aim to examine technical variations between sessions associated with and without adverse effects, to optimise safety and refine the technique.