Chair: Andreas Kopf, Germany
Neurophysiological approach to central pain
Luis Garcia-Larrea, France
Functional imaging and central pain
Roland Peyron, France
Functional imaging of central (neuropathic) pain have previously pointed out some brain regions as being abnormally activated during allodynic pain. These regions are the parietal operculum (SII) and the anterior insular cortex, bilaterally and thalamus contralateral to pain. Here we present a new set of data obtained in 35 patients with central neuropathic pain studied with fMRI with the aim to precise brain reorganizations that may underlie the allodynic sensation. We recorded BOLD signal changes during a 30 minutes fMRI session in which tactile and/or cold rubbing stimulations were applied on the painful side of the body. Two conditions were compared to rest, a painful one in which stimulation was applied on an allodynic area of the body (A) and a definitely less painful one (C) in which the same stimulus was applied on a non-allodynic area. As for previous studies, the allodynic condition was associated with additional activations in anterior operculo-insular cortex, mid-cingulate and SMA. These regions are supposed to be involved in the transformation of the rubbing sensation into an allodynic one. Additional correlation analyses will allow to answer whether or not these changes are related to pain intensity or to sensory deafferentation. These results will be presented with respect to what is known from the physiological functions attributed to these cortical areas, especially regarding pain processes.