Cerebral perfusion in posterior reversible encephalopathy syndrome measured with arterial spin labeling MRI

Abstract

Background and purpose: The pathophysiologic basis of posterior reversible encephalopathy syndrome (PRES) remains controversial. Hypertension (HTN)-induced autoregulatory failure with subsequent hyperperfusion is the leading hypothesis, whereas alternative theories suggest vasoconstriction-induced hypoperfusion as the underlying mechanism. Studies using contrast-based CT and MR perfusion imaging have yielded contradictory results supporting both ideas. This work represents one of the first applications of arterial spin labeling (ASL) to evaluate cerebral blood flow (CBF) changes in PRES.

Materials and methods: After obtaining Institutional Review Board approval, MRI reports at our institution from 07/2015 to 09/2020 were retrospectively searched and reviewed for mention of "PRES" and "posterior reversible encephalopathy syndrome." Of the resulting 103 MRIs (performed on GE 1.5 Tesla or 3 Tesla scanners), 20 MRIs in 18 patients who met the inclusion criteria of clinical and imaging diagnosis of PRES and had diagnostic-quality pseudocontinuous ASL scans were included. Patients with a more likely alternative diagnosis, technically non-diagnostic ASL, or other intracranial abnormalities limiting assessment of underlying PRES features were excluded. Perfusion in FLAIR-affected brain regions was qualitatively assessed using ASL and characterized as hyperperfusion, normal, or hypoperfusion. Additional quantitative analysis was performed by measuring average gray matter CBF in abnormal versus normal brain regions.

Results: HTN was the most common PRES etiology (65%). ASL showed hyperperfusion in 13 cases and normal perfusion in 7 cases. A hypoperfusion pattern was not identified. Quantitative analysis of gray matter CBF among patients with visually apparent hyperperfusion showed statistically higher perfusion in affected versus normal appearing brain regions (median CBF 100.4 ml/100 g-min vs. 61.0 ml/ 100 g-min, p < 0.001).

Conclusion: Elevated ASL CBF was seen in the majority (65%) of patients with PRES, favoring the autoregulatory failure hypothesis as a predominant mechanism. Our data support ASL as a practical way to assess and noninvasively monitor cerebral perfusion in PRES that could potentially alter management strategies.

Keywords: ASL; Arterial spin labeling; CBF; Cerebral blood flow; PRES; Posterior reversible encephalopathy syndrome.

Fig. 1

Study flow diagram.

Fig. 2

Axial T2 FLAIR (left) and ASL perfusion maps (middle and right) in a 23-year-old female with Tacrolimus-induced PRES. Hyperperfusion (white arrowheads) is noted corresponding to the regions of parieto-occipital FLAIR hyperintensity (yellow arrowheads). Regions-of-interest (ROI) are depicted for hyperperfusion (white outline) and normal perfusion (yellow outline). Note that ROIs extend into adjacent slices (not shown). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Axial T2 FLAIR (left) and ASL color (right) perfusion maps in an 18-year-old female with eclampsia induced PRES. No convincing altered perfusion was seen on ASL corresponding to the regions of FLAIR hyperintensity (yellow arrowheads) or elsewhere. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 4

A representative example of both matched and unmatched ASL and FLAIR abnormality. Axial T2 FLAIR (left) and ASL color (right) perfusion maps in a 59-year-old male with HTN-induced PRES. Hyperperfusion (white arrowheads) is noted corresponding to the regions of FLAIR hyperintensity (orange arrowheads). Hyperperfusion without any corresponding FLAIR hyperintensity is seen in the left basal ganglia (blue arrowhead). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Axial T2 FLAIR (left) and ASL color (right) perfusion maps on day 1 (top row) and day 3 (bottom row) of a 33-year-old male with methamphetamine-induced PRES. Hyperperfusion (white arrowheads) was near-completely resolved three days after the initial presentation while FLAIR hyperintensity (orange arrowheads) persisted. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 6

Box-and-whisker plot of quantitative CBF in thirteen PRES patients with visually apparent hyperperfusion. CBF in regions of hyperperfusion relative to normal perfusion (control) is found statistically different at p < 0.001. Boxes depict interquartile range. Whiskers depict minimum and maximum values, excluding a paired outlier (plus signs).