EXPERIMENTAL CRANIAL PAIN ELICITED BY CAPSAICIN - A PET STUDY

Using a positron emission tomography (PET) study it was shown recently that in migraine without aura certain areas in the brain stem were ac tivated during the headache state, but not in the headache free interv al. It was suggested that this brain stem activation is inherent to th e migraine attack itself and represents the so called 'migraine genera tor'. To test this hypothesis we performed an experimental pain study in seven healthy volunteers, using the same positioning in the PET sca nner as in the migraine patients. A small amount of capsaicin was admi nistered subcutaneously in the right forehead to evoke a burning painf ul sensation in the first division of the trigeminal nerve. Increases of regional cerebral blood flow (rCBF) were found bilaterally in the i nsula, in the anterior cingulate cortex, the cavernous sinus and the c erebellum. Using the same stereotactic space limits as in the above me ntioned migraine study no brain stem activation was found in the acute pain state compared to the pain free state, The increase of activatio n in the legion of the cavernous sinus however, suggests that this str ucture is more likely to be involved in trigeminal transmitted pain as such, rather than in a specific type of headache as was suggested for cluster headache. (C) 1998 International Association for the Study of Pain. Published by Elsevier Science B.V.