The Detection of Small-Fiber Neuropathies in Burning Mouth Syndrome and Iatrogenic Lingual Nerve Injuries: Use of Quantitative Sensory Testing

Aims: To assess thermal pain perception in patients with burning mouth syndrome (BMS) and lingual nerve injury (LNI) by using a quantitative sensory testing (QST) protocol. Methods: QST was used to assess cool, warm, cold pain, and heat pain thresholds in healthy control subjects (n = 17) and in patients with BMS (n = 22) and LNI (n = 47). Capsaicin (10 μg/mL) and ethyl chloride-evoked hypersensitivities at the anterior two-thirds of the tongue were measured using a visual analog scale. Data were analyzed using Microsoft Excel with descriptive statistics, scatter graphs, and two-tailed Student t tests with 95% confidence interval and 5% level of significance. Results: Patients with BMS significantly reported the most pain at rest (P .001) and capsaicin hypersensitivity (P .01). Despite this increased sensitivity to capsaicin and significantly lower warm threshold than the control subjects (P .05), these patients did not show heat pain hyperalgesia. There was increased sensitivity to ethyl chloride and cold pain hyperalgesia in patients with BMS (P .05) compared with reduced or no sensation of cold or heat pain in patients with LNI. Conclusions: This study has demonstrated that the assessment of capsaicin and ethyl chloride- evoked sensitivities as well as the use of QST to assess thermosensitivity are useful approaches for detecting hyperalgesia or hypoalgesia to heat and cold in patients with BMS and LNI. Keywords: burning mouth syndrome, hyperalgesia, hypoalgesia, lingual nerve injury, quantitative sensory testing