Venous disease of the brain has been underestimated and under recognized but the ease and accuracy with which MR and multidetector computed tomography venography (MDCTV) can display the veins has raised awareness and appreciation of this previously overlooked entity. MDCTV is the only technique which is not affected by flow, filling all veins everywhere equally, and so it displays the complete venous anatomy. Variations in cerebral venous anatomy are more prevalent than arterial variations, and as neurosurgeons are becoming more aware of the complications secondary to venous occlusion, they frequently request MDCTV prior to complex surgery. The full extent of congenital or acquired venous stenosis/occlusion is only demonstrable with MDCTV, as with DSA only part of the venous system is filled from each artery injected.

Cerebral venous thrombosis is now recognized as a common disease with a much better prognosis than was reported when the diagnosis depended upon invasive DSA. Plain unenhanced CT will demonstrate acute thrombus in the veins and MDCTV the extent of the new and preexisting thrombosis. The possibility of venous disease must always be kept in mind in the setting of acute stroke and in assessing any cerebral haemorrhage or thunderclap headache. MDCTV also has a new useful role to play in the assessment of idiopathic intracranial hypertension.

Simple enhanced CT is not a substitute for CT venography which requires this specific technique if errors are to be avoided.

Table 11.1 presents optimal patient preparation, and the protocol is presented in Table 11.2. A surview for CT venography is shown in 11.1.

The series of axial scans can be displayed as seven combined images to give a manageable number for viewing either on film or PACS system. The window centre and width can be adjusted to show the contrast in the venous sinuses throughout the brain.

Base image review with wide windows, e.g. 350 window; 100 level to allow differentiation of venous sinus enhancement from the adjacent bone; this is essential as it is possible to diagnose venous thrombosis on axial image review without any more complex reformations (11.1 B-D). MIP and VR3D are also useful.