Intracranial Atherosclerosis: Incidence, Diagnosis and Treatment

Intracranial atherosclerosis is considered a cause of approximately 8% of all strokes in the western society. However, its frequency is much higher in Asian countries. In our hospital-based study, among the patients who had angiographic abnormalities, the frequency of intracranial atherosclerosis was approximately 70% far exceeding that of extratracranial atherosclerosis. Symptomatic atherosclerotic diseases were most often found in the middle cerebral artery. Generally, it has been shown that obesity and hyperlipidemia are related to extracranial diseases while advance hypertension is associated with intracranial diseases. However, these results have not always been replicated, and certain genetic factors may be related with the ethnic differences in the location of atherosclerosis. Recent studies using diffusion weighted MRI showed that the main mechanisms of stroke in patients with intracranial atherosclerosis are the branch occlusion, artery to artery embolism and both. The intracranial stenosis, especially symptomatic one, is not a static condition and may progress or regress in a relatively short period of time. Progressive stenosis of intracranial arteries is clearly related to the development of ischemic events. The annual risk of stroke relevant to the stenosed intracranial vessel is approximately 8%. In retrospective studies including ASID, anticoagulation was found to be superior to aspirin in reducing the stroke events. However, a recent prospective study failed to confirm the superiority of anticoagulation over aspirin in patients with intracranial stenosis. Moreover, anticoagulation resulted in excessive central nervous system bleeding as compared to aspirin. Because aspirin alone seems to be insufficient in the prevention of progression of intracranial stenosis, a combination of antiplatelets has been tried. Recently, we found that a combination of aspirin + cilostazol was superior to aspirin monotherapy in the prevention of progression of symptomatic intracranial stenosis. However, further studies are required to find out the best combination of antiplatelets for symptomatic intracranial stenosis. The effect of other atheroma stabilizers such as statins should also be properly evaluated. Angioplasty/stent is another important option for the relatively severe intracranial stenosis. According to previous studies, immediate success rate has reached up to 90%. If patients are carefully selected, and procedures done by experienced hand, angioplasty/stent can be of benefit especially in relatively young patients with proximal, short-segment, severe symptomatic stenosis. However, this procedure is not without complications or long-term re-stenosis. Further studies are required to elucidate the best therapeutic strategy in patients with intracranial atherosclerosis.