Abstracts

Rationale: Posterior reversible encephalopathy syndrome (PRES) is defined by a potentially reversible vasogenic edema with a predilection of parenchyma supplied by the posterior circulation. The major symptoms of PRES are headache, decreased alertness, cortical blindness and seizures. Although clinical and radiologic findings have been well recognized, atypical imaging findings and nonreversible clinical course were increasingly reported, including subsequent epilepsy. In order to better understand the radiological and clinical spectrum of PRES in children, we conducted a retrospective multicenter study. Methods: We studied 30 patients who were diagnosed with PRES at pediatric departments of 13 affiliated hospitals of Nagoya university and Nagoya City University from 1999 to 2012. Child neurologists reviewed the clinical charts and neuroimaging findings. We investigated the underlying disorders, previous use of immunosuppressive agents, clinical symptoms, blood pressure at the onset, and brain MRI findings. We also reviewed the presence of neurological sequelae, epilepsy and nonreversible MRI lesions during follow-up period. Results: The age of the patients at the onset ranged from 3 to 22 years of age (median 8 years). Underlying disorders were neoplasm in 19 patients, renal disease in 8, collagen disease in 3, and the others (bronchial asthma, congenital immunodeficiency, hemophagocytic syndrome). Although 29 patients had high blood pressure at the onset, the degree of the hypertension was variable. Twenty three patients had seizures, 19 had alteration of consciousness, 6 had headache and 4 had visual disturbances. The MRI lesions were observed in occipital lobes in 29 patients, parietal lobes in 22, frontal lobes in 6, and temporal lobes in 6. Five patients had MRI lesions in cerebellum and 1 had in thalamus and basal ganglia. Apparent diffusion coefficient (ADC) map was constructed in MRI studies of 26 patients, and 6 of them revealed decreased ADC values at the lesions. Twenty four patients had follow-up MRI studies, and 5 of them had focal gliosis and cortical atrophy. In 6 patients with ADC reduction during the acute period, 4 patients had follow-up studies and 3 of them had gliosis and atrophy. On the other hand, all patients with normal or increased ADC values during acute period showed no abnormalities on the follow-up MRI. During follow-up period, 4 patients had focal epilepsy. Three of them had decreased ADC values at the onset. Two patients had occipital lobe epilepsy, and epilepsy focus was unknown in the other 2. Conclusions: While high ADC values suggest reversible vasogenic edema, decreased ADC values indicate irreversible cytotoxic edema. Evaluation of ADC values on MRI during acute period has a good predictive value for nonreversible MRI lesions and subsequent onset of epilepsy.