Prognostic Observation of Posterior Reversible Encephalopathy Syndrome

Background and Significance

Posterior Reversible Encephalopathy Syndrome (PRES) is a clinical-radiological syndrome. It was first described by Hinchey et al. in 1996. It is characterized by a variable combination of headaches, seizures, altered mental status, visual impairment, nausea, vomiting and focal neurological signs and accompanied with symmetric vasogenic edema of bilateral posterior cerebral circulation territory. PRES is associated with multiple risk factors, such as renal dysfunction, hypertension, cytotoxic drugs, autoimmune disease and pre-eclampsia or eclampsia, which can occur in a wide range of diseases and predisposing factors. Lesions are usually located in the parietal occipital region. However, lesions may also involve unilateral cerebral hemisphere, anterior circulation area or deep brain structure. According to the location of the lesions, five distribution patterns were described: mainly parietal-occipital pattern, superior frontal sulcus pattern, holo-hemispheric watershed pattern, partial or asymmetric expression of the primary patterns and central pattern. In addition, cytotoxic edema with associated diffusion restriction, abnormal enhancement due to blood brain barrier disruption, hemorrhages, infarction are atypical findings which may be occasionally detected.

PRES is associated with a variety of clinical conditions. The occurrence of PRES is not affected by age and gender, it may present in all age groups. The occurrence of PRES may be a result of either breakdown of cerebral autoregulation and disruption of blood brain barrier, causing vasogenic edema or endothelial dysfunction resulting from circulating toxic mediators, sepsis, autoimmune conditions, or eclampsia. Up to now, the pathophysiological mechanism of PRES is still not clear, but cerebral autoregulation impairment and endothelial dysfunction are considered to be the most important potential mechanisms.

PRES usually has a favourable prognosis. The clinical and imaging findings are often reversible when the underlying causes are eliminated and the blood pressure is controlled. Even so, many patients still have permanent neurological sequelae and have a mortality of 5%-15%. Known risk factors for PRES include hypertension, renal disease and immunosuppressive therapy, and researchers have also found that lymphopenia and dyslipidemia are the potential risk factors for PRES. The prognostic factors of PRES include the presence of PRES risk factors, duration of symptoms, the presence of cytotoxic edema and hemorrhage. Alhilali et al. through the retrospective analysis of the etiologies, imaging findings and cerebrospinal fluid examination of the 47 PRES patients with lumbar puncture showed that clinical factors, imaging findings, cerebrospinal fluid laboratory results all affect the prognosis of PRES, with low CSF glucose, hypertensive encephalopathy, and imaging findings of hemorrhage increasing the risk of fatal outcome, while toxemia of pregnancy was found to have a relatively protective effect. Recent research had shown correlation of MRI findings and LDH and albumin levels, suggesting that these biochemical indices may be used as a prognostic factor. Although the various risk factors of PRES and its related imaging findings are well described, and in previous studies, the relationship between clinical factors, imaging findings, laboratory examination results and prognosis of PRES were analyzed respectively by different investigators, their relative effects on the prognosis are remain unclear and there are no consistent conclusions about it.

Here we use a multi-center approach to conduct this study to ensure a larger patients sample. This proposed multi-center retrospective study will analyze the factors that influence the prognosis of the patients with PRES. The aim of our research is to study the connection between different causes, different imaging findings, laboratory findings and clinical outcome in patients with PRES and deepen the understanding of the nature of PRES. The pathogenesis of PRES will be further discussed based on the results obtained. This will contribute to predict the prognosis of patients with PRES and to further investigate the pathogenesis of PRES so as to guide the clinical treatment and follow-up evaluation.