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Spreading waves of transient and prolonged decreases in water diffusion after subarachnoid hemorrhage in rats

Diffusion‐weighted MRI (DWI), which can detect cortical spreading depressions (SDs) as propagating waves of reduced apparent diffusion coefficient (ADC) of water, was used to investigate whether spreading depression occurs after subarachnoid hemorrhage (SAH) induced by endovascular perforation in the rat. Eleven rats underwent SAH while positioned in the magnet. The ADC measurements had a temporal resolution of 12 sec. Transient decreases in ADC to 74 ± 5% of pre‐SAH values were observed in three rats after SAH, which propagated over the cortex with an average speed of 4.2 ± 0.6 mm/min, consistent with an SD wave. Furthermore, in all 11 rats, a wavefront of reduced ADC, which did not resolve within the 12 min observation period, spread at a speed of 3.2 ± 1.7 mm/min in the ipsilateral cortex, and again is consistent with the speed of SD propagation. Therefore, spreading depression–like cellular depolarization is a consequence of acute subarachnoid hemorrhage in rats. Magn Reson Med 44:110–116, 2000. © 2000 Wiley‐Liss, Inc.