Association of Collateral Blood Vessels Detected by Arterial Spin Labeling Magnetic Resonance Imaging With Neurological Outcome After Ischemic Stroke

Abstract

Importance: Robust collateral blood vessels have been associated with better neurologic outcome following acute ischemic stroke (AIS). The most commonly used methods for identifying collaterals are contrast-based angiographic imaging techniques, which are not possible in all patients after AIS.

Objective: To assess the association between the presence of collateral vessels identified using arterial spin labeling (ASL) magnetic resonance imaging, a technique that does not require exogenous administration of contrast, and neurologic outcome in patients after AIS.

Design, setting, and participants: This retrospective cohort study examined 38 patients after AIS admitted to a tertiary academic medical center between 2012 and 2014 who underwent MRI with ASL.

Main outcomes and measures: According to a prespecified hypothesis, ASL images were graded for the presence of collaterals by 2 neuroradiologists. Modified Rankin Scale (mRS) scores at discharge and other composite data were abstracted from the medical record by a neurologist blinded to radiologic data.

Results: Of the 38 patients, 19 (50.0%) were male, and the mean (SD) age was 61 (20) years. In 25 of 38 patients (65.8%), collaterals were detected using ASL, which were significantly associated with both a good outcome (mRS score of 0-2 at discharge; P = .02) and a 1-point decrease in mRS score at discharge (odds ratio, 6.4; 95% CI, 1.7-23.4; P = .005). In a multivariable ordinal logistic regression model, controlling for admission National Institutes of Health Stroke Scale score, history of atrial fibrillation, premorbid mRS score, and stroke parent artery status, there was a strong association between the presence of ASL collaterals and a 1-point decrease in the mRS score at discharge (odds ratio, 5.1; 95% CI, 1.2-22.1; P = .03).

Conclusions and relevance: Following AIS, the presence of ASL collaterals is strongly associated with better neurological outcome at hospital discharge. This novel association between ASL collaterals and improved neurologic outcome may help guide prognosis and management, particularly in patients who are unable to undergo contrast-based radiological studies.

Figure 1.. Three Patients With Acute Ischemic Stroke and a Range of Collateral Arterial Transit Artifact (ATA) Signal on Arterial Spin Labeling (ASL)

A, Patient 1. Left, Diffusion-weighted imaging (DWI) showing multifocal infarcts (arrowheads) throughout the right middle cerebral artery (MCA) territory. Right, ASL showing a large area of decreased cerebral blood flow (CBF) without ASL collaterals (ASLcs). Arrowheads indicate the absence of ATA hyperintensity, which was present on all ASL images. B, Patient 2. Left, DWI showing a right basal ganglia infarct (arrowhead). Right, ASL showing a larger area of decreased CBF with moderate ASLcs (arrowheads). C-H, Patient 3. Computed tomographic (CT) angiogram of the neck (not shown) showed occluded left internal carotid artery. C, CT angiogram of the brain showing excellent leptomeningeal collateral vessels (arrowheads) distal to the occlusion. D, DWI showing the cortical area of infarct in the left MCA territory. E-H, ASL showing decreased CBF in the left MCA territory, with a pattern of subtle ASLcs seen on multiple slices (arrowheads).

Figure 2.. Box Plot of Modified Rankin Scale (mRS) Scores in Patients With vs Without Arterial Spin Labeling Collaterals (ASLcs)

The box plots demonstrate a lower median mRS score in the group with ASLcs (z, 3.0; P = .005). The box indicates the interquartile range (25/75); error bars, range; white dot, the median. MRI indicates magnetic resonance imaging.