Treatment and imaging of intracranial atherosclerotic stenosis: current perspectives and future directions

Abstract

Background and purpose: Intracranial atherosclerosis is a common cause of stroke worldwide. It results in ischemic stroke due to different mechanisms including artery-to-artery embolism, in situ thrombo-occlusion, occlusion of perforating arteries, and hemodynamic failure. In this review, we present an overview of current treatment and imaging modalities in intracranial atherosclerotic stenosis.

Methods: PubMed was searched for relevant articles in English that evaluated the treatment and imaging of intracranial atherosclerotic stenosis (ICAS).

Results: Aggressive medical management, consisting of dual antiplatelet therapy and intensive risk factor management, is important in patients with ICAS because of a substantial risk of recurrent stroke, approximately 20% in the first year, in patients on aspirin or warfarin alone. Recent trials have suggested that, aggressive medical therapy results in better outcome as compared with intracranial stenting. However, the question remains what the optimal treatment strategy would be in patients with recurrent strokes in the setting of failed aggressive medical therapy. Moreover, controversy exists whether a subgroup of patients with symptomatic ICAS could benefit from intracranial stenting if selection is based on radiological evidence of hemodynamic failure. With regard to imaging, transcranial Doppler ultrasound and magnetic resonance angiography are useful screening tests for exclusion of ICAS, but need confirmation by other imaging modalities when stenosis is suggested. Computed tomography angiography has a high positive and negative predictive value for detection of intracranial luminal stenosis of 50% or higher, but performs worse than digital subtraction angiography with regard to establishing the exact degree of luminal stenosis. Novel imaging techniques including high-resolution CT and MRI better identify plaque characteristics than conventional imaging methods.

Conclusions: Currently, aggressive medical management remains the standard of care for patients with ICAS. Further research is needed to identify high-risk subgroups and to develop more effective treatments for ICAS patients.

Keywords: intracranial atherosclerosis; intracranial stenosis; ischemic stroke.

Figure 1

Catheter angiogram showing 90% stenosis of the right middle cerebral artery. “Reprinted from Holmstedt et al. (2013) with permission from Elsevier”

Figure 2

Magnetic resonance angiography showing a flow gap in the right middle cerebral artery in a patient with a recent right hemisphere infarct. This gap suggests a flow‐limiting stenosis, but the degree of stenosis cannot be accurately measured “Reprinted from Holmstedt et al. (2013) with permission from Elsevier”

Figure 3

High‐resolution MRI of vertebral artery stenoses with plaque components Panels A–D show T2‐weighted and T1 postcontrast images (panels C and D have plaque components marked) of a crosssection of a vertebral artery plaque with a thick, intact, fibrous cap (gray) and lipid core (white with black asterisk). Panels E–H show T2‐weighted and T1 postcontrast images (panels G and H have plaque components marked) of a cross section of a vertebral artery plaque with a ruptured fibrous cap (gray) and lipid core (white with black asterisk), which enhances with contrast (white asterisk) and is also indicative of plaque rupture. The solid white line shows the outside vessel wall and the dashed white line the lumen “Reprinted from Holmstedt et al. (2013) with permission from Elsevier”