Changes in cerebral perfusion after osmotherapy in acute, cerebral stroke measured by perfusion-weighted MRI

We investigate the hemodynamic changes after osmotherapy in patients with acute cerebral stroke. Measurement of mean transit time (MTT), regional cerebral blood volume (rCBV) and regional cerebral blood flow (rCBF) with perfusion-weighted MRI. During a bolus injection of 0.1 mmol/kg Gadolinium-DTPA a series of transversal T2*-weighted FLASH-images was recorded. Based on the indicator dilution theory MTT, rCBV and rCBF were calculated and displayed in a parameter map. In 11 patients showing local brain edema caused by cerebral infarction this technique was applied before and 30 minutes after intravenous infusion of 125 ml of 40% sorbitol. Before treatment eight patients showed pronounced inhomogeneous distribution of MTT and rCBV with increased rCBV ipsilateral to the Lesion. rCBF was only slightly reduced in the ipsilateral hemisphere. After treatment the side to side differences of rCBV and MTT were significantly (p<0.05) reduced. Perfusion-weighted MRI appears as a suitable method to assess the hemodynamic changes in patients with cerebral stroke. rCBV seems to be more influenced by acute locale brain edema than rCBF The elevation of rCBV and MTT can be explained by an impaired, but compensated perfusion, which normalizes after osmotherapy.