PAIN-EVOKED BLINK REFLEX

The electrically evoked blink reflex (BR) consists of an ipsilateral R 1 component (R1) at 11 ms and two bilateral components R2 at 33 ms and R3 at 83 ms. It is still unclear whether the R2 is mediated by activa tion of tactile or nociceptive afferents. For testing the nociceptive hypothesis, nociceptors of the supraorbital nerve were selectively act ivated by infrared laser stimuli in 10 subjects. Only painful laser st imuli evoked a bilateral early polyphasic BR response (LR2) at 71 ms. Stimulation of infraorbital and mental nerve dermatomes was equally ef fective. A tate bilateral reflex response at 130 ms was occasionally o bserved. Regarding the nociceptor activation time of about 40 ms, onse t latencies were within the range of the electrically evoked R2 and R3 , respectively. The good accordance of R2 and LR2 may be due to activa tion of identical nociceptive fibers or to convergence of electrically evoked tactile and laser-elicited nociceptive input onto common multi receptive neurons. (C) 1997 John Wiley & Sons, Inc.