Diagnostic Imaging on Intracranial Atherosclerotic Stenosis

1. Diagnostic Imaging on Intracranial Atherosclerotic Stenosis • Eduardo Freire Mello • Department of Interventional Neuroradiology • Hospital Espanhol, Salvador - BA, Brasil • edufmello@ig.com.br

2. Introduction • Intracranial Atherosclerotic Disease accounts for 6 - 10% of all Ischemic Strokes in whites, and may be responsible for 22 - 26% of all IS in Asians • 15% risk of recurrent stroke per year • Under-recognized cause of stroke • Recent advances on clinical and interventional treatment • Accurate radiological diagnosis and quantification of the lesions is crucial for treatment planning

3. So, non-invasive methods are required ! DSA • Gold-standard, but.... • Most expensive, invasive and time consuming • Stroke risk of 0,7% with permanent disability

4. Transcranial Doppler • Least invasive and expensive test • Highly operator-dependent • Low reproducibility • Not technicaly feasible in all patients • Not possible to image every vessel

5. MRA X CTA • CTA is less susceptible to motion artifacts and less dependent on hemodynamic effects • Approach of all proximal portions of the intracranial vasculature with a proper CTA examination and processing techniques • Some recent studies have compared the accuracy of MRA and CTA, alone or combined, to DSA (gold-standard)....

6. In 2002 Hirai et al. demonstrated that: • MRA alone < CTA + MRA • MRA alone has a lower spatial resolution as compared with CTA or DSA, and can cause overestimation of stenosis • Accuracy of MRA + CTA ≅ DSA in measuring stenosis and detecting occlusions of the major intracranial arteries AJNR Am J Neuroradiol 23:93-101, January 2002

7. In 2008 Nguyen-Huynh et al. evaluated the accuracy of CTA for Intracranial Atherosclerotic Disease, comparing to DSA: • CTA detected large artery occlusion with 100% sensitivity and specificity • For detection of > 50% stenosis CTA had 97,1% sensitivity and 99,5% specificity, and a NPV of 99,8% Stroke. 2008; 39:1184-1188 • In 2005 Bash et al. compared CTA with MRA, using DSA as a gold-standard: • CTA has a higher sensitivity, specificity and PPV for the evaluation of intracranial stenoocclusive disease AJNR Am J Neuroradiol 26:1012-1021, May 2005

8. In 2007 Villablanca et al. compared MDCT Angiography to DSA for detection and quantification of small intracranial arteries, and concluded: • MDCT Angiography depicted 90% or more of all examined small intracranial arteries detected with DSA • The smallest arterial size reliably detected with CTA was 0,7mm versus 0,4mm for DSA AJR 2007; 188: 593-602

9. CTA`s disadvantages • Radiation exposure • Time and skill involved in image processing • Use of contrast material • Possible venous contamination in a region of interest • No significant flow information

10. Conclusion • CTA seems to be more accurate than MRA to evaluate intracranial atherosclerotic stenosis • CTA can be relatively comparable to DSA and presents fewer risks, less costs, is more frequently available and is highly accurate • CTA may be considered as the primary study in the setting of suspected intracranial atherosclerotic stenosis