Intracranial atherosclerosis: From anatomy to pathophysiology

Area of Science:

• Neurology
• Vascular Medicine
• Medical Imaging

Background:

• Intracranial atherosclerotic stenosis (ICAS) is a major cause of ischemic stroke.
• Traditionally, stenosis severity guides treatment, but it inadequately reflects ischemia risk.
• Hemodynamic factors like collateral circulation and perfusion are more critical indicators.

Purpose of the Study:

• To review novel angiographic methods for assessing the functional severity of ICAS.
• To discuss the limitations and future prospects of these methods.

Main Methods:

• Review of techniques for estimating cerebral blood flow, including signal intensity ratio, computational fluid dynamics, pressure wires, and quantitative magnetic resonance angiography.
• Evaluation of fractional flow as a measure of hemodynamic status and collateral circulation.

Main Results:

• Fractional flow parameters may indicate collateral circulation and blood flow status, but accuracy requires validation.
• Current methods for fractional flow reserve in cardiovascular disease are not directly applicable to cerebrovascular disease.
• Pressure wire measurement of fractional flow in ICAS is technically feasible and safe.

Conclusions:

• Cerebral blood flow and stenosis severity have an individualized relationship.
• Hemodynamic criteria are essential for screening patients for endovascular treatment.
• Optimizing diagnosis and treatment strategies for symptomatic ICAS requires a shift towards hemodynamic assessment.