Quantitative somatic sensory testing and functional imaging of the response to painful stimuli before and after cingulotomy for obsessive-compulsive disorder (OCD)

Postoperatively, the patient demonstrated increased intensity and unpleasantness ratings of painful thermal waterbath stimuli. The PET studies demonstrated preoperative contact heat pain-evoked activation of the bilateral MCC/SMA (supplementary motor area) and the left (contralateral) fronto-parietal operculum. Postoperative pain-evoked activation was demonstrated in the right (ipsilateral) parasylvian cortex but not of the MCC/SMA. Prior studies of forebrain lesions, and of cortical synchrony during the application of painful stimuli suggest the presence of functional connectivity between components of the MCC/SMA and the fronto-parietal opercula. Therefore present results suggest that cingulate lesions disinhibit ipsilateral parasylvian cortex and so are independent evidence of functional connectivity between these cortical areas, the defining characteristic of modules in a pain network.