INHIBITION OF THE BLINK REFLEX R2 COMPONENT AFTER SUPRAORBITAL AND INDEX FINGER STIMULATIONS IS REDUCED IN CLUSTER HEADACHE - AN INDICATIONFOR BOTH SEGMENTAL AND SUPRASEGMENTAL DYSFUNCTION

Peripheral as well as central mechanisms are thought to play a role in cluster headache pathogenesis. We have studied recovery curves of the R2 component of the blink reflex after conditioning by supraorbital o r index finger stimuli in 10 episodic cluster headache (CH) patients d uring a cluster period and in 10 healthy controls. There was no signif icant change of R2 threshold, latency or area in CH patients. After pa ired supraorbital stimuli, R2 recovered more rapidly in patients on th e symptomatic side. After index stimulations, R2 recovery was more rap id on both symptomatic and non-symptomatic sides in patients compared to controls. Naloxone (0.4 mg) i.v. in two subjects partially reversed the R2 suppression induced by index finger stimuli. The unilateral de crease of R2 inhibition after a segmental supraorbital stimulus most l ikely reflects sensitisation in the spinal trigeminal nucleus. Whether the latter is due to irritation of the ophthalmic nerve within the ca vernous sinus region, which is thought to be pivotal in CH pathogenesi s, remains to be proven. In addition, we propose that the bilateral de ficit of R2 inhibition after an extrasegmental exteroceptive stimulus might reflect hypoactivity of reticular nuclei, possibly because of re duced central opioid activity. (C) 1997 International Association for the Study of Pain.