Cerebral Hypoperfusion in Posterior Reversible Encephalopathy Syndrome is Different from Transient Ischemic Attack on CT Perfusion.

BACKGROUND: PRES is a reversible neurotoxic state presenting with headache, altered mental status, visual loss, and seizures. Delayed diagnosis can be avoided if radiological patterns could distinguish PRES from cerebral ischemia. METHODS: Clinical and radiological data were collected on all hospitalized patients who had (1) discharge diagnosis of PRES and (2) acute CTP/CTA. Data were compared with 10 TIA patients with proven cytotoxic edema on MRI. RESULTS: Of the four PRES patients found, three were correlated with acute blood pressure and one with chemotherapy. At the radiological level, quantitative analyses of the CTP parameters showed that 2 out of 4 patients had bilaterally reduced CBF-values (23.2-47.1 ml/100g/min) in occipital regions, as seen in the pathological regions of TIA patients (27.3 ± 13.5 ml/100g/min). When compared with TIA patients, the pathological ROI's demonstrated decreased CBV-values (3.4-5.6 ml/100g). Vasogenic edema on MRI FLAIR imaging was seen in only one PRES patient, and cytotoxic edema on DWI-imaging was never found. CT angiography showed in one PRES patient a vasospasm-like unilateral posterior cerebral artery. CONCLUSIONS: If confirmed by other groups, CTP and CTA imaging in patients with acute visual loss and confusion may help to distinguish PRES from bi-occipital ischemia. These radiological parameters may identify PRES patients at risk for additional tissue infarction.