Lisette van Dam

Imaging modalities for diagnosing cerebral vein thrombosis 7 117 CT venography CT venography is one of themost often used imagingmodalities for the diagnosis of CVT because of its widespread availability and cost-effectiveness. 5 CT venography is a contrast-enhanced helical CT examination performed with a time-optimized contrast bolus in order to enhance the cerebral venous system. 17,42 The diagnosis of CVT can be made by evaluation of the axial thin-section contrast-enhanced source images of a helical CT scan. However, two- and three-dimensional (2D and 3D) reformation techniques (e.g. maximum intensity projection, integral display, and volume rendering) can be used to provide detailed anatomic images of the deep and superficial cerebral veins free from overprojecting bones and brain parenchyma. 17,43 On CT venography, a thrombosed cerebral vein can be visualized as a filling defect ( Figure 1B ). 5,9 Also indirect signs of CVT such as brain edema and subarachnoid haemorrhage can contribute to the diagnosis of CVT. 2,5 In the most relevant studies available, CT venography was found to be a reliable alternative to DSA for diagnosing CVT 41,44,45 with a sensitivity and specificity of both 100%. 44 However, quality of this evidence is low, since individual studies included less than 100 patients, were observational and suffered from a high risk of bias. 41 Other studies used consensus reading of multiple imaging modalities and final clinical outcome as reference standard rather than DSA ( Appendix 3 ). 10,21,46 In these studies, CT venography was found to be accurate for diagnosing cerebral sinus thrombosis as well, with a sensitivity of 100% (95%CI 88-100%) and specificity of 100% (95%CI 95-100%). 10,21,46 However, these studies were also small (n < 34) and retrospective. Notably, CT venography has been shown to be of limited diagnostic value for diagnosing cortical vein thrombosis with a reported sensitivity of 6-75%. 21,46 This is explained by the fact that the ‘missing vein’, i.e. contrast filling defect, is difficult to distinguish from physiological variations in venous anatomy. 21 Thus, available literature supports the use of CT venography for diagnosing cerebral sinus thrombosis, but less so for cortical vein thrombosis. 21 Emerging CT techniques In past years new CT techniques have been developed that may allow better diagnosis of CTV. With the emerge of multidetector row CT (MDCT), thin slices are obtained with the use of less contrast and shorter scanning time allowing better