TRANSIENT CELL DEPOLARIZATION AFTER PERMANENT MIDDLE CEREBRAL-ARTERY OCCLUSION - AN OBSERVATION BY DIFFUSION-WEIGHTED MRI AND LOCALIZED H-1-MRS

Focal cerebral ischemia causes rapid intensity changes in diffusion-we ighted images (DWI) and elevated lactate as detected by localized prot on spectroscopy (H-1-MRS). To investigate whether such changes can als o be evoked by periischemic depolarizations, we combined DWI and H-1-M RS measurements with DC potential recordings. About 40 min after occlu sion of the middle cerebral artery in a rat, a negative DC deflection was observed indicating transient cell depolarization. Coincidentally with the depolarization a transient increase of the DWI signal intensi ty and a partially reversible increase of lactate occurred in the peri phery of the ischemic territory. These results show that peri-ischemic depolarization, known to contribute to the evolution of cerebral infa rction, evokes disturbances that can be detected by DWI and H-1-MRS.