The Detection of Small-Fiber Neuropathies in Burning Mouth Syndrome and latrogenic 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 mu g/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.