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In a series of 102 patients with angiographically proven cerebral sinus venous thrombosis (SVT) significant differences with arterial cerebrovascular disease were noted with respect to disease onset, reversibility of symptoms, occurrence of epileptic seizures and headache, cerebral blood flow under resting and stimulated conditions, occurrence of intracranial bleedings, and response to heparin therapy. From these findings pathophysiological differences are hypothesized: Whereas arterial cerebral ischemia usually is a monophasic abrupt thrombotic process and there is only a small penumbra, SVT is a continuing process of disequilibrium between prothrombotic and thrombolytic mechanisms; large areas of the brain are only functionally or metabolically disturbed but not irreversibly damaged. Intracranial bleeding in SVT is a consequence of increased venous and capillary pressure and thus occurs more frequently than in arterial thrombotic disease in which capillary pressure is reduced by the thrombosis and bleeding occurs during reperfusion of tissue damaged by ischemia. Heparin treatment in SVT is effective since it shifts the equilibrium away from the prothrombotic side and is able to save large areas of brain tissue that are only reversibly damaged. It improves venous outflow and thus decreases the risk of intracranial hemorrhage, in contrast with the arterial thrombotic disease where heparin increases the risk or at least the severity of intracranial bleedings.