Recent studies have renewed interest in the role of limbic structures, such as the cingulate cortex, in nociception. To investigate the involvement of the limbic system in pain and temperature perception further, we have quantified ratings of innocuous and noxious thermal stimuli in a patient with schizoaffective disorder before and after 2 surgical procedures. Psychophysical tests were conducted at a control session prior to surgery. Postoperative test sessions were conducted up to 10 weeks after bilateral cingulotomy and for 3 months after a subsequent bilateral anterior internal capsulotomy. A contact thermal stimulator delivered ascending (39-50 degrees C) and descending (22-2 degrees C) series of stimuli to the patient's volar forearm. The patient was trained to rate the innocuous warmth and cold and the pain associated with each stimulus. A cold presser test was used to obtain a measure of cold pain tolerance. Compared to pre-operative levels, cingulotomy/capsulotomy resulted in moderately diminished warmth perception and an elevated heat pain threshold and increased ratings to suprathreshold noxious heat stimuli (hyperpathia). Prior to surgery, the patient perceived all cold stimuli as cold but not painful. However, after cingulotomy and capsulotomy, cold stimuli were rated significantly colder and stimuli less than or equal to 12 degrees C evoked pain. Compared to normal control subjects, the patient's ratings of innocuous and noxious cold stimuli were reduced pre-operatively but elevated postoperatively and cold pain tolerance was elevated pre-operatively but reduced postoperatively. These altered ratings of noxious heat and cold stimuli were reflected on both a pain intensity and pain affect (unpleasantness) scale. In summary, these data suggest that cingulotomy and capsulotomy disinhibited the patient's noxious heat and cold appreciation. These findings provide support for a role of the cingulate cortex and frontal cortical regions in the perception of innocuous and noxious thermal stimuli and suggest that under normal conditions, these areas may act to suppress the subjective intensity of noxious heat and cold.
