Cerebral hemodynamics and stroke risks in symptomatic intracranial atherosclerotic stenosis with internal versus cortical borderzone infarcts: A computational fluid dynamics study

Abstract

There may be different mechanisms underlying internal (IBZ) and cortical (CBZ) borderzone infarcts in intracranial atherosclerotic stenosis. In 84 patients with symptomatic, 50-99% atherosclerotic stenosis of M1 middle cerebral artery (MCA-M1) with acute borderzone infarcts in diffusion-weighted imaging, we classified the infarct patterns as isolated IBZ (n = 37), isolated CBZ (n = 31), and IBZ+CBZ (n = 16) infarcts. CT angiography-based computational fluid dynamics models were constructed to quantify translesional, post-stenotic to pre-stenotic pressure ratio (PR) in the MCA-M1 lesion. Those with IBZ infarcts were more likely to have a low PR (indicating impaired antegrade flow across the lesion) than those without (p = 0.012), and those with CBZ infarcts were more likely to have coexisting small cortical infarcts (indicating possible embolism) than those without (p = 0.004). In those with isolated IBZ or CBZ infarcts, low PR was independently associated with isolated IBZ infarcts (adjusted odds ratio = 4.223; p = 0.026). These two groups may also have different trajectories in the stroke risks under current medical treatment regimen, with a higher risk of same-territory ischemic stroke recurrence within 3 months in patients with isolated IBZ infarcts than isolated CBZ infarcts (17.9% versus 0.0%; log-rank p = 0.023), but similar risks later in 1 year.

Keywords: Borderzone infarct; cerebral hemodynamics; intracranial atherosclerotic disease; ischemic stroke; prognosis.

Figure 1.

Flow chart of this study. IBZ: internal borderzone; CBZ: cortical borderzone.

Figure 2.

Pressure distribution across symptomatic M1 segment of middle cerebral artery (MCA-M1) stenosis in the computational fluid dynamics (CFD) models (left panel) and the infarct patterns in diffusion-weighted images (DWI, right panel) in 3 patients. Translesional pressure ratio (PR)= Pressure _{post-stenotic} /Pressure _pre-stenotic . Locations for measuring the Pressure _{post-stenotic} and Pressure _pre-stenotic in the CFD models are marked with arrows 1 and 2, respectively. a. Low PR (PR=0.71) of left MCA-M1 stenosis noted in the CFD model, indicating a significant pressure gradient and hence impaired antegrade flow across the lesion. Multiple small chain-like infarcts noted in the left IBZ in DWI. b. Normal PR (PR=0.96) of right MCA-M1 stenosis noted in the CFD model, indicating a small translesional pressure gradient. Wedge-shaped infarcts noted in the right anterior and posterior CBZ noticed in DWI. c. Low PR (PR=0.42) of left MCA-M1 stenosis noted in the CFD model, indicating a significant pressure gradient and hence impaired antegrade flow across the lesion. Wedge-shaped infarcts in the left posterior CBZ and multiple small chain-like infarcts noted in the ipsilateral IBZ.

Figure 3.

Cumulative probabilities of recurrent ischemic stroke in the same territory (SIT) within 3 months (a) and 1 year (b) in patients with isolated internal borderzone (IBZ) or cortical borderzone (CBZ) infarcts at baseline. a. Significant difference in the cumulative risks of recurrent SIT within 3 months in patients with isolated IBZ and CBZ infarcts at baseline (17.9% versus 0.0%; log-rank p = 0.023). b. The cumulative risks of recurrent SIT within 1 year were not significantly different between patients with isolated IBZ and CBZ infarcts at baseline (21.4% versus11.1%; log-rank p = 0.271). Of note, the difference in the cumulative risks between the two groups seems narrowed beyond the first 3 months.