or abscess. The ‘empty delta sign’ on CT, reflecting the opacification
of collateral veins in the wall of the superior sagittal
sinus after contrast injection, is present in only 10–20% of
cases. CT is entirely normal in 10–20% of proven CVST [1].
CTV has been shown in at least one series [19] to be superior
to MRV in visualizing sinuses or smaller cerebral veins or
cortical veins with low flow. Examination of the cerebrospinal
fluid remains important in the appropriate clinical context
to rule out meningitis or subarachnoid hemorrhage before
the diagnosis of CVST has been established. Its other value
is in patients who are thought to have benign intracranial
hypertension where the presence of any abnormal findings
in the CSF should point at CVST as the underlying cause
of raised pressure. All other investigations are directed to
demonstrating the underlying cause. Clinically obvious cases
such as local infection or head injury may be self-evident,
whereas extensive investigations are needed in the idiopathic
cases. Suspicion of malignancies or connective tissue diseases
should be confirmed with appropriate tests. Coagulation
studies are important, particularly in patients with a family
or medical history of thrombotic episodes in addition to the
unexplained cases. The investigations should include a search
for the factor V Leiden mutation if resistance to activated
protein C is abnormal, and