Cerebral Sinus and Venous Thrombosis in Rats Induces Long-Term Deficits in Brain Function and Morphology—Evidence for a Cytotoxic Genesis

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Abstract
The pathophysiology of cerebral venous infarctions is poorly understood, due partially to the lack of a suitable experimental model. Therefore, we developed a model in rats to study acute and long-term changes of brain function and morphology following thrombosis of the superior sagittal sinus. The superior sagittal sinus of rats was exposed, ligated, and injected with thrombogenic material. Thrombosis of the longitudinal sinus and ascending cortical veins was monitored by intravital fluorescence angiography. Histology was studied at 24 h and 4 weeks after thrombosis and changes in intracranial pressure, electroencephalogram (EEG), and tissue impedance were noted. Spontaneous locomotor activity was followed for 4 weeks after thrombosis. The effect of heparin treatment on tissue impedance was evaluated. Thrombosis of the superior sagittal sinus could be regularly induced, although pathological sequelae developed only if ascending veins were affected. Sinus and venous thrombosis was histologically characterized by bilateral, parasagittal infarctions. Thrombosis induction was followed by an increase in intracranial pressure from 4.7 ± 1.6 to 12.8 ± 2.4 mm Hg (n = 4) at 1 h after thrombosis, associated with an exponential rise in tissue impedance to 165 ± 14% (n = 8) of the control. EEG changes were similar to those following global cerebral ischemia and remained pathological for up to 6 months after thrombosis (n = 6). As a permanent behavioral deficit spontaneous locomotor activity was reduced to 60 ± 10% (n = 6) of the control. Finally, the administration of heparin (1 IU/g body weight) after thrombosis induction was found to reverse the pathological tissue impedance response of the brain. In conclusion, involvement of ascending cortical veins following sinus thrombosis appears to be critical for the development of irreversible tissue damage, such as infarction. Changes in intracranial pressure and tissue impedance suggest that the venous thrombosis was followed by brain edema of a predominantly cytotoxic nature. Venous thrombosis led to long-term changes of brain function, as demonstrated by persistent disturbances of the EEG or of the spontaneous locomotor drive. These deficits may be amenable to treatment with heparin.