Posterior reversible encephalopathy syndrome: utility of fluid-attenuated inversion recovery MR imaging in the detection of cortical and subcortical lesions

Abstract

Background and purpose: Posterior reversible encephalopathy syndrome (PRES) is typically characterized by headache, altered mental functioning, seizures, and visual loss associated with imaging findings of bilateral subcortical and cortical edema with a predominantly posterior distribution. Our goal was to determine whether fluid-attenuated inversion recovery (FLAIR) imaging improves the ability to detect subtle peripheral lesions of PRES, as compared with conventional MR techniques.

Methods: Sixteen patients with clinical and imaging findings consistent with PRES were studied. Thirteen patients had undergone transplantation and had cyclosporin A neurotoxicity. Fast-FLAIR images were compared with spin-echo proton density- and T2-weighted images.

Results: FLAIR imaging improved diagnostic confidence and conspicuity of the T2 hyperintense lesions of PRES, typically in the subcortical white matter of the parietooccipital regions bilaterally. On all 23 abnormal MR studies, FLAIR was judged superior to proton density- and T2-weighted images for the detection of PRES in the supratentorial brain. In a mean of 6.7 of 23 studies, FLAIR findings prompted a raise in the grade of disease severity. FLAIR also showed cortical involvement in 94% of patients with PRES and in a mean of 46% of the total lesion burden. In four cases, subtle lesions were virtually undetectable without FLAIR. Brain stem or cerebellar disease was encountered in 56% of patients.

Conclusion: FLAIR improves the ability to diagnose and detect subcortical and cortical lesions in PRES as compared with proton density- and T2-weighted spin-echo images. We therefore believe that FLAIR should be performed in patients with suspected PRES to allow more confident recognition of the often subtle imaging abnormalities.

fig 1.

Case 12: 13-year-old girl with systemic lupus erythematosus who presented with hypertension and status epilepticus. MR imaging was performed 5 days later. A–C, FLAIR axial sections show extensive subcortical white matter edema bilaterally (arrows) with only minimal cortical involvement. Lesions are in the parietal, occipital, posterior frontal, and posterior temporal lobes and in the left corona radiata (asterisk). Additional T2 hyperintensity is seen in the white matter around the lentiform nuclei (arrowheads). Findings are consistent with typical changes of PRES, especially in the parietooccipital regions, and were considered moderate (severity index = 2) for the purposes of this study. D and E, Follow-up MR study obtained 150 days after initial neurologic examination reveals complete resolution of lesions on FLAIR images.

fig 2.

Case 8: 48-year-old woman with history of vasculitis and chronic renal failure who presented with seizures. A, Initial MR study, FLAIR sequence, reveals typical subcortical edema of PRES in the left posterior frontal lobe (arrow). This patient also had mild cortical involvement of the parietooccipital regions, the left posterior temporal lobe, and the left thalamus. These findings were assigned a severity ranking of 2 (moderate disease). B, Follow-up FLAIR image 5 days after original presentation. Although the left posterior frontal subcortical edema has resolved, there was an overall progression of the findings of PRES with new right posterior frontal cortical hyperintensity (arrows). C, FLAIR image, at same level, 7 days after original presentation, shows mild worsening of edema, now bifrontal, with some new subcortical foci (arrowheads). D, T2-weighted image shows new bilateral cerebellar hyperintense foci (arrows). E, Cerebellar lesions are seen better on FLAIR image (arrows). This patient has parietooccipital lesions typical of severe PRES. Extension of edema to involve the cerebellum bilaterally was considered to warrant a severity index of 3 (severe disease).

fig 3.

Case 4: 10-year-old boy being treated with CSA for bone marrow transplantation for acute lymphocytic leukemia. Shortly before imaging, the patient had two episodes of focal seizures and acute hypertension coincident with seizure activity. The serum CSA level was normal at the time the seizures occurred. Before the day of imaging, the patient had been normotensive. A, Axial proton density–weighted image. B, Axial T2-weighted image at same level. C, FLAIR image at same level as A and B reveals cortical T2 hyperintensity in a gyral pattern bilaterally in the occipitoparietal lobes (arrows). D, Axial FLAIR image, superior to A, suggests additional subtle cortical hyperintensity along gyri of the left parietal and posterior frontal lobes (arrows). This type of subtle cortical involvement was given a severity rating of 1 (mild disease).

fig 4.

Case 11: 48-year-old man being treated with CSA who presented with generalized seizures shortly before imaging. A and B, Proton density–weighted (A) and axial T2-weighted (B) sections reveal a nonspecific punctate white matter hyperintensity (arrow) in the left parietal lobe. C, Corresponding turbo-FLAIR image shows biparietal increased signal within the cortex (white arrows) and subcortical white matter (black arrow), representing edema and suggesting the radiologic diagnosis of PRES. D and E, Adjacent proton density–weighted (D) and T2-weighted (E) images, one level superiorly, show increased cortical (white arrows) and subcortical white matter signal due to edema. F, Turbo-FLAIR image at same level again reveals the cortical-based hyperintensities that are difficult to appreciate on standard dual-echo sequences, owing to the adjacent bright CSF. FLAIR unmasks this abnormality by suppressing CSF signal. This case was assigned a moderate severity score on the basis of the FLAIR imaging findings, although on the basis of proton density–or T2-weighted images it would have been considered mild.

fig 5.

Mean of the percentage of PRES lesion distribution with respect to gray and white matter. Mean percentages were also calculated for each severity subgroup and for all cases. There was a trend toward greater white matter involvement with increasing disease severity. The overall mean percentage of lesions was 46% in the gray matter and 54% in the white matter