Prevention of both T-2- and diffusion-weighted increases in image intensity during cerebral hypoxia-ischemia in infant rats pretreated with dexamethasone

The present study examines the effect of dexamethasone treatment on the int ensity of changes in T-2-weighted and diffusion-weighted (DW) magnetic reso nance images occurring in infant rats during and after cerebral hypoxia-isc hemia. The right carotid artery was occluded under isoflurane anesthesia in 7-day-old rats and images were acquired in sedated animals using a Bruker 9.4 T magnetic resonance (MR) system, Imaging changes were markedly differe nt in rats pretreated with dexamethasone phosphate (0.1 mg/kg, i.p.) 24 h b efore hypoxia than in controls. In control animals, areas of hyperinensity ipsilateral to the occlusion occurred during hypoxia-ischemia in both the D W- and T-2-weighted images with some recovery of the changes in early posth ypoxia. In contrast, in dexamethasone-treated animals, areas of increased h yperintensity in the MR images did not occur. Thus, dexamethasone treatment prevents MR imaging changes during ischemia, suggesting that the cytotoxic edema associated with energy depletion and/or ionic disturbances during is chemia are also prevented by dexamethasone treatment.