Epileptic Ictal Hyperperfusion on Arterial Spin Labeling Perfusion and Diffusion-Weighted Magnetic Resonance Images in Posterior Reversible Encephalopathy Syndrome.

Background: The hemodynamic state of the posterior dominant vasogenic edema in posterior reversible encephalopathy syndrome (PRES) is controversial. The aim of this retrospective study was to examine the contribution of epileptic ictal hyperperfusion in patients with PRES using combined magnetic resonance perfusion imaging with arterial spin labeling (ASL) and diffusion-weighted magnetic resonance imaging (MRI).

Methods: A detailed review of chronological MRI findings in 2 patients, including diffusion-weighted imaging (DWI) and ASL, with special reference to clinical and electroencephalographic findings, was performed. At the onset of PRES, both patients developed secondary generalized seizures.

Results: At the first PRES episode in Case 1, ASL and DWI clearly depicted "ictal hyperperfusion" and prolonged epilepsy-induced cytotoxic edema in the left parieto-occipital lobe cortex, located around the vasogenic edema of the PRES lesion in the left occipital lobe (hypoperfused area). At the second and third episodes (2 and 7 months after the first episode, respectively), although recurrent PRES was ruled out, ASL and DWI clearly demonstrated ictal hyperperfusion in the left posterior temporal and parieto-occipital lobes associated with partial nonconvulsive status epilepticus, which developed around the PRES-related old hematoma lesion. In Case 2, peri-ictal MRI findings of ictal ASL hyperperfusion and cortical hyperintensity on DWI were also noted in the left parieto-occipital lobe, but were mild compared with Case 1.

Conclusions: Combined use of DWI and ASL can provide information on hemodynamic state associated with epileptic ictal hyperperfusion in the various phases of PRES.