A new method to increase nociception specificity of the human blink reflex

Objective: The medullary R2 response of the blink reflex can be elicited by innocuous and noxious stimuli. The purpose of this study was to elicit a nociception specific R2 response with a new surface electrode. Methods: In 10 healthy subjects the blink reflex was elicited using a standard (10–15 mA) and a new concentric surface electrode type (0.6–1.6 mA) which produces a pin-prick-like pain. Results: After topical local anaesthesia with lignocaine/prilocaine R1 was unchanged, R2 was attenuated by 12% after standard stimulation but was almost abolished (−91%) with the new electrode type. Conclusion: Stimulation with low stimulus intensities but electrode-dependent high current density allows preferential depolarization of superficial nociceptive A-delta fibres. This new method is less traumatic than others and is useful in the study of trigeminal nociception.