Blink Reflexes in Patients with Atypical Odontalgia

Aims: To use the human blink reflex (BR) to explore possible neuropathic pain mechanisms in patients with atypical odontalgia (AO). Methods: In 13 AO patients, the BR was elicited using a concentric electrode and recorded bilaterally with surface electromyographic (EMG) electrodes on both orbicularis oculi muscles. Electrical stimuli were applied to the skin above branches of the V1, V2, and V3 nerves and to the V branch contralateral to the painful branch. Sensory and pain thresholds were determined. The BR examination of the painful V branch was repeated during a capsaicin pain-provocation test. The data were analyzed with nonparametric statistics. Results: The BR responses (R2 and R3) evoked by stimulation of V3 were significantly smaller than the BR responses evoked by stimulation of V1 and V2 (P .004). There were no differences in BR (R2 or R3) between the painful and nonpainful sides (P > .569), and the BR (R2 and R3) was not significantly modulated by experimental pain (P > .080). The sensory thresholds were significantly lower on the painful side compared to the nonpainful side (P = .014). The pain thresholds were not different between sides (P > .910). Conclusion: No major differences between the V nociceptive pathways on the right and left sides were found in a relatively small group of AO patients. Future studies that compare BRs in AO patients and healthy volunteers are needed to provide further knowledge on the pain mechanisms in AO. Keywords: atypical odontalgia, blink reflex, capsaicin, pain, trigeminal nociception