PATHOPHYSIOLOGICAL ASPECTS OF CEREBRAL SINUS VENOUS THROMBOSIS (SVT)

In a series of 102 patients with angiographically proven cerebral sinu s venous thrombosis (SVT) significant differences with arterial cerebr ovascular disease were noted with respect to disease onset, reversibil ity of symptoms, occurrence of epileptic seizures and headache, cerebr al blood flow under resting and stimulated conditions, occurrence of i ntracranial bleedings, and response to heparin therapy. From these fin dings pathophysiological differences are hypothesized : Whereas arteri al cerebral ischemia usually is a monophasic abrupt thrombotic process and there is only a small penumbra, SVT is a continuing process of di sequilibrium between prothrombotic and thrombolytic mechanisms ; large areas of the brain are only functionally or metabolically disturbed b ut not irreversibly damaged. Intracranial bleeding in SVT is a consequ ence of increased venous and capillary pressure and thus occurs more f requently than in arterial thrombotic disease in which capillary press ure is reduced by the thrombosis and bleeding occurs during reperfusio n 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 d amaged. It improves venous outflow and thus decreases the risk of intr acranial hemorrhage, in contrast with the arterial thrombotic disease where heparin increases the risk or at least the severity of intracran ial bleedings.