FMRI CHANGES IN THE BRAIN ASSOCIATED WITH THE CAROTID COMPRESSION TEST

Purpose: The purpose of our investigation was to study in normal volun teers the response to a unilateral common carotid (CC) compression tes t using dynamic MRI sensitive to variations in blood magnetic suscepti bility. Method: Nine volunteers, positioned in a 1.5 T MR scanner, per formed a unilateral 40 to 45 s CC self-compression during the acquisit ion of single slice axial T2-weighted FLASH images, Results: In three subjects, the signal showed a significant 2% drop from baseline in th e ipsilateral frontal temporal cortex during the compression. In anoth er three subjects, a significant 1.5-2% signal decrease was observed i n both hemispheres. In two subjects whose MR angiography showed abnorm alities of the circle of Willis, the bilateral signal drop was more re markable (3%). In one volunteer, the signal did not change. Conclusion : Increased deoxyhemoglobin within the brain microcirculation is the p robable explanation for the signal drop. This method could be further tested in view of the widespread use of open interventional MR units.