Early development of vasogenic edema in experimental cerebral fat embolismin cats - Correlation with MRI and electron microscopic findings

RATIONALE AND OBJECTIVES. To evaluate the magnetic resonance imaging and el ectron microscopic findings of the hyperacute stage of cerebral fat embolis m in cats and the time needed for the development of vasogenic edema. METHODS. Magnetic resonance imaging was performed at 30 minutes (group 1, n = 9) and at 30 minutes and 1, 2, 4, and 6 hours after embolization with tr iolein (group 2, n = 10). As a control for group 2, the same acquisition wa s obtained after embolization with polyvinyl alcohol particles (group 3, n = 5). Magnetic resonance images were analyzed qualitatively and quantitativ ely. Electron microscopic examination was done in all cats. RESULTS. In group 1, the lesions were iso- or slightly hyperintense on T2-w eighted (T2W) and diffusion-weighted (DWIs) images, hypointense on the appa rent diffusion coefficient (ADC) map image, and markedly enhanced on the ga dolinium-enhanced Tl-weighted images (Gd-T1WIs). In group 2 at 30 minutes, the lesions were similar to those in group 1. Thereafter, the lesions becam e more hyperintense on T2WIs and DWIs and more hypointense on the ADC map i mage. The lesions were enhanced on Gd-T1WIs at all acquisition times. In gr oup 3, the lesions showed mild hyperintensity on T2WIs at 6 hours but hypoi ntensity on the ADC map image from 30 minutes, with a tendency toward a gre ater decrease over time. The lesions were not enhanced on Gd-T1WIs at any t ime point. Electron microscopic findings revealed discontinuity of the capi llary endothelial wall, perivascular and interstitial edema, and swelling o f glial and neuronal cells in groups 1 and 2. Cellular swelling and interst itial edema were more prominent in group 2. In group 3, interstitial edema was seen; however, discontinuity of the endothelial wall was absent. CONCLUSIONS. The lesions were hyperintense on T2WIs and DWIs, hypointense o n the ADC map image, and enhanced on Gd-T1WIs. On electron microscopy, the lesions showed cytotoxic and vasogenic edema with disruption of the blood-b rain barrier. Vasogenic edema seems to develop within 30 minutes in cerebra l fat embolism in cats.