Cerebral blood flow territory instability in patients with atherosclerotic intracranial stenosis

Abstract

Background: Stroke risk stratification in patients with symptomatic intracranial atherosclerotic arterial disease (ICAD) remains an important clinical objective owing to the high 14-19% recurrent stroke rate in these patients on standard-of-care medical management. There thus remains a need for hemodynamic markers that may allow for the selection of personalized therapies for high-risk symptomatic patients.

Purpose: To determine if shifting of cerebral blood flow (CBF) territories in response to changes in cerebral perfusion pressure (CPP) may provide a marker for stroke risk in ICAD patients.

Study type: Prospective.

Population: Twenty ICAD patients who experienced a stroke within 45 days of study enrollment and 10 healthy controls.

Sequence: 3.0T MRI including anatomical imaging (T₁ -weighted, T₂ -weighted/FLAIR), 3D MR angiography, and normocapnic and hypercapnic vessel-encoded CBF-weighted arterial spin labeling.

Assessment: Patients were scanned within 45 days of overt stroke and monitored (duration = 13.2 ± 4.4 months) for the endpoint of non-cardioembolic stroke or transient ischemic attack. Flow territory shifting (shifting index) was calculated from the first scan by determining whether a voxel shifted from its primary arterial source from normocapnia to hypercapnia.

Statistical tests: A Mann-Whitney U-test (significance: P < 0.05) was performed to determine whether patients meeting the endpoint had greater shifting indices relative to controls or patients not meeting the endpoint.

Results: Shifting indices (mean ± standard error) were significantly higher in patients meeting endpoint criteria relative to controls (P = 0.0057; adjusted P = 0.036) and patients not meeting endpoint criteria (P = 0.0047; adjusted P = 0.036).

Data conclusion: Flow territory shifting may provide a marker of recurrent stroke risk in symptomatic ICAD patients on standard-of-care medical management therapies.

Level of evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1441-1451.

Keywords: arterial spin labeling; cerebral blood flow; flow territories; intracranial stenosis; stroke.