Pathological considerations
The venous territories of the brain are less well defined than
arterial territories due to the presence of extensive anastomoses
between cortical veins. These allow the development of
collateral circulation in the event of an occlusion. The main
cerebral venous sinuses affected by CVST are the superior
sagittal sinus (72%) and the lateral sinuses (70%). In about
one-third of cases more than
one sinus is affected [4]. In a
further 30–40%, both sinuses
and cerebral or cerebellar
veins are involved [1,4]. CVST
has been described as a continuing process in which the
balance of prothrombotic and thrombolytic processes is disturbed,
leading to progression of the venous thrombus with
time [2]. This slow growth of the thrombus and the good
collateralization of the venous vessels probably explain the
gradual onset of symptoms, often over weeks and months
[1,2]. Sudden onset, however, has been described [5]. From
the large number of patients with complete reversibility of
their neurological deficit, it can be inferred that there must be