Abstract PR334

Abstract

Background & Objectives: Up to 24% of patient post hysterectomy in KK Women’s and Children’s Hospital in Singapore end up with chronic pain. This study aims to evaluate cerebral blood flow (CBF) changes in the pain network using Arterial Spin Labelling (ASL), a non-invasive MRI technique able to quantify tissue perfusion, in women post hysterectomy when they are subjected to a painful thermal stimulus. Materials & Methods: This study was approved by the institutional review board and written consent was obtained. Pain-free women post hysterectomy (aged 38 to 67 years; average 49.7 years; median 48 years) were invited for MRI brain imaging on a 3T MR scanner with a 32-channel phased-array receive-only head coil. All subjects had 44 degrees of heat applied to the left thigh via a thermode during the MRI ASL scan. Subject’s pain score during the pain stimulation process was continuously recorded by Computerized Visual Analog Scale (COVAS). Significant pain experience was defined as more than 30% increase in pain score on the COVAS system. During the thermal stimulation, a total of 81 pairs of control-labelled ASL images were acquired using 3D-PASL sequence with temporal resolution of 8 seconds for each pair. Heat stimulation was applied for the 8th to 59th pairs of control-labelled images, while the first 7 pairs and the last 22 pairs of control-labelled images were obtained without heat stimulation. Results: Nineteen women underwent the MRI scans with 44 degrees thermal stimulation successfully. Seven women experienced significant pain as captured on the COVAS system during the pain stimulation process, while 12 did not experience significant pain. Significantly increased CBF was reflected in the pain network centres in all who experienced pain on COVAS. Those who did not experience pain on COVAS only had significant increased CBF in the right insula and cingulate. There was only statistical difference in the thalamus (p=0.03), post central gyrus (p=0.04) and frontal pole (p=0.04) when the CBF changes in the pain network were compared between those who experienced significant pain against those who did not. Conclusion: In women subjected to heat/pain stimulus, ASL is able to demonstrate statistically significant increased CBF in the thalamus, post central gyrus and frontal pole which matches the subjective pain experienced by the patient as captured on COVAS score. The relatively increased CBF experienced in the right thalamus and right insula would correspond to the heat thermode being placed on the left thigh.