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

Diffusion-weighted MRI (DWI), which can detect cortical spreading depressio ns (SDs) as propagating waves of reduced apparent diffusion coefficient (AD C) of water, was used to investigate whether spreading depression occurs af ter subarachnoid hemorrhage (SAM) induced by endovascular perforation in th e at. Eleven rats underwent SAH while positioned in the magnet. The ADC mea surements had a temporal resolution of 12 sec. Transient decreases in ADC t o 74 +/- 5% of pre-SAM values were observed in three rats after SAH, which propagated over the cortex with an average speed of 4.2 +/- 0.6 mm/min, con sistent with an SD wave. Furthermore, in all 11 rats, a wavefront of reduce d ADC, which did not resolve within the 12 min observation period, spread a t a speed of 3.2 +/- 1.7 mm/min in the ipsilateral cortex, and again is con sistent with the speed of SD propagation. Therefore, spreading depression-l ike cellular depolarization is a consequence of acute subarachnoid hemorrha ge in rats. (C) 2000 Wiley-Liss, Inc.