Pathogenesis of venous stroke: evaluation with diffusion- and perfusion-weighted MRI.

Previous reports have demonstrated the diagnostic usefulness of diffusion- and perfusion-weighted magnetic resonance imaging (MRI) in the evaluation of cerebral venous thrombosis. However, the explanations ascribed for the pathophysiologic mechanisms of venous stroke in these reports were conflicting. Earlier reports supported prominent vasogenic edema associated with mild cytotoxic edema as the potential pathophysiologic mechanism. More recently, a few reports have found cytotoxic edema as the cause for venous stroke. The purpose of this report is to review the pathogenesis of cerebral venous thrombosis after taking into consideration the results of MRI findings. We report two cases of cerebral venous infarction, which had worsening symptoms and signs that resolved after intravenous heparin therapy. In both cases, findings on diffusion-weighted and perfusion-weighted MRI images were compatible with vasogenic edema and viable neuronal tissue. Both the patients recovered without any significant residual sequel. We support the hypothesis that in the pathogenesis of venous stroke vasogenic edema is the initial event, which may or may not be followed by cytotoxic edema eventually evolving to an infarction.