Delayed CSF Enhancement in Posterior Reversible Encephalopathy Syndrome

Abstract

SUMMARY:We present a case of increased fluid-attenuated inversion recovery signal intensity in the subarachnoid spaces on 6-hour delayed enhanced MR imaging in a patient with posterior reversible encephalopathy syndrome (PRES) in the setting of acute hypertensive encephalopathy. This hyperintensity was believed due to CSF gadolinium enhancement, a finding that would be anticipated in light of the suspected pathogenesis of increased microvascular permeability in PRES. Posterior reversible encephalopathy syndrome (PRES) is theorized to result from an abnormally leaky blood-brain barrier (BBB) at the level of the microvasculature. MR perfusion studies to date have unsuccessfully clarified the site of abnormally increased vascular permeability as capillary, arteriolar, or venular.1 Increased permeability to small molecules such as water explain the interstitial accumulation of fluid in areas affected by PRES; however, larger molecules such as gadolinium chelates might also cross an abnormally permeable BBB. Because this leak may occur slowly for minutes to hours, it is difficult to capture with dynamic contrast-enhanced perfusion techniques or even immediate postcontrast sequences. We report a case of abnormal fluid-attenuated inversion recovery (FLAIR) hyperintensity in the subarachnoid spaces in a patient with PRES and normal renal function. The hyperintensity was due to delayed CSF gadolinium accumulation, a finding that supports the concept of slow BBB leakage in this syndrome. Case ReportA 77-year-old woman with a medical history significant for chronic hypertension and dementia presented to the emergency department with headache, obtundation, and markedly elevated blood pressures as high as 230/120 mm Hg. Unenhanced FLAIR imaging of the brain performed at this time demonstrated extensive confluent areas of white matter hyperintense signal intensity in both cerebral hemispheres (Fig 1). Diffusion-weighted images and apparent diffusion coefficient maps (not shown) demonstrated increased diffusion in the affected areas and no restricted diffusion. The clinical presentation and MR imaging findings were consistent with PRES in the setting of hypertensive encephalopathy.The patient underwent a second contrast-enhanced MR imaging examination, including perfusion imaging 6 hours later on the same date. Axial FLAIR images of the brain obtained immediately following the second dose of contrast revealed markedly elevated signal intensity throughout the subarachnoid spaces, which had not been present on the first study (Fig 2). CT was not performed due to no clinical concern for subarachnoid hemorrhage and given the normal-appearing FLAIR images at the time of initial presentation and imaging. A CSF assay for gadolinium was also not performed to confirm the suspicion that FLAIR hyperintensity was due to enhancement because no other indications for the procedure were sufficient to warrant consideration of this mildly invasive test.The patient's admission and subsequent laboratory values revealed no evidence for renal compr...

Posterior Reversible Encephalopathy Syndrome: Clinicoradiological Spectrum and Therapeutic Strategies

“…5 In 1 report, diffuse CSF enhancement was observed on fluid-attenuated inversion recovery image 6 hours after the initial gadolinium administration, supporting an increased microvascular permeability to allow a slow infiltration of large molecules, such as gadolinium, through the BBB. 30 The frequency and specificity of this image finding in PRES merits further confirmatory studies.…”

Neuroimaging features in posterior reversible encephalopathy syndrome: A pictorial review

“…Increased fluidattenuated inversion recovery signal intensity in the subarachnoid spaces on delayed enhanced MR imaging is also possible, believed due to cerebrospinal fluid gadolinium enhancement. 66 …”

The posterior reversible encephalopathy syndrome: what's certain, what's new?

“…Postcontrast FLAIR weighted imaging is not usually performed but it has been suggested to be more sensitive in detecting superficial abnormalities than conventional postcontrast T1 weighted MRI 21. Two recently published case reports have shown enhancement of the subarachnoid space on postcontrast FLAIR imaging, supporting the theory that permeability changes in the blood–brain barrier do occur 21 22…”