Posterior reversible encephalopathy syndrome: A review with emphasis on neuroimaging characteristics

doi:10.1016/j.jns.2019.07.018

Journal of the Neurological Sciences

Volume 404, 15 September 2019, Pages 72-79

https://doi.org/10.1016/j.jns.2019.07.018 Get rights and content

Highlights

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Typical MRI findings of PRES in parieto-occipital lobes caused by vasogenic edema.
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Atypical PRES cases show brainstem, basal ganglia, and cerebellum.
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Endothelial dysfunction may be the predominant pathophysiological mechanism of PRES.
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MRI findings have been useful for the prompt diagnosis of PRES.
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MRI findings play a central role in constructing the algorithm.

Abstract

Posterior reversible encephalopathy syndrome (PRES) is a clinical and radiological condition that involves the acute onset of headache, confusion, optical impairments, and seizures with accompanying vasogenic edema on brain imaging. PRES is a complex disorder with many causative factors, including underlying conditions such as hypertensive encephalopathy, eclampsia, collagen disease, and severe infection. Although the exact pathophysiological mechanism is not completely understood and remains controversial, the predominant proposed mechanism is endothelial dysfunction, which is preceded by hypertension, immunosuppressive agents, or cytotoxic medication. Magnetic resonance imaging (MRI) facilitates prompt diagnosis and treatment and leads to good outcomes. Findings are characterized by the following: hyperintensity on fluid-attenuated inversion recovery images and apparent diffusion coefficient mapping, and isointensity on diffusion weighted images involving the parieto-occipital or posterior frontal cortical–subcortical regions that are recognized in >90% of patients, and reversibility of neuroimaging abnormalities, with the latter being the most important. As an algorithm to standardize the diagnosis of PRES has not yet been developed, this review presents a diagnostic algorithm based on the types of MRI findings. This algorithm may provide a better understanding of the characteristics that compose PRES and bring us one step closer to the standardization of PRES diagnosis, helping clinicians evaluate individual features while also considering competing differential diagnoses.

Introduction

Over two decades have passed since posterior reversible encephalopathy syndrome (PRES) was first described in 1996 [1]. PRES is a neurological condition characterized by the acute onset of signs and symptoms that include seizures, disturbances to consciousness, headache, optical impairments and by neuroimaging findings of reversible subcortical vasogenic edema. Increasing use of brain magnetic resonance imaging (MRI) over the past two decades has led to the increased recognition of PRES, and clinicians in various fields encounter patients with PRES. The pathophysiology of PRES is not completely understood and remains controversial [2]. PRES is generally considered to be both radiologically and clinically reversible and typically has a good prognosis. However, diffuse edema or hemorrhage may cause complications or long-term neurological deficits, making accurate diagnosis of PRES essential for rapid and appropriate treatment to improve patient results and minimize complications. Therefore, it is necessary to investigate the imaging findings, clinical signs, and biochemical parameters of PRES to further predict prognosis. As there are currently no standard guidelines or diagnostic criteria for PRES, a diagnostic algorithm would help advance the radiological and pathophysiological research of this syndrome.

This review aims to present the pathophysiological, clinical, and radiological features and diagnostic approaches of PRES, emphasizing the clinical significance of imaging findings and their utility in developing a diagnostic algorithm.

Section snippets

Etiology and pathophysiological hypothesis

There are several comorbid conditions that may accompany PRES, including hypertension (53% of reported clinical cases), kidney disease (45%), malignancy (32%), dialysis dependency (21%), and transplantation (24%) [3,4]. The various factors that can cause PRES are presented in Table 1. Underlying conditions include hypertensive encephalopathy, eclampsia, collagen disease, and severe infection, and hemolytic uremic syndrome and thrombotic thrombocytopenic purpura are important contributing

The clinical features of PRES

The main clinical symptoms of PRES are headaches, convulsions, disturbances to consciousness, and optical impairments [14]. Both focal and generalized epileptic seizures are very common and have been recognized in approximately two-thirds of all patients [4,15]. Optical symptoms are thought to be caused by functional impairments of the occipital lobe. Disturbances to consciousness may appear to varying degrees. There are also manifestations of hemiplegia, ataxia, and involuntary movements.

The neuroradiological features of PRES

MRI is used to perform neuroimaging and is more sensitive for hyperintense lesions in T2-weighted or FLAIR sequences. The typical imaging findings of PRES are most apparent as hyperintensity on FLAIR images in the parieto-occipital and posterior frontal cortical and subcortical white matter (Fig. 2); less commonly, the brainstem, basal ganglia, and cerebellum are involved. Typical imaging findings for PRES are observed in the low-density area mainly around the white matter of the occipital and

Other clinical examination features of PRES

Recently, three retrospective cohort studies investigated the spectrum of cerebrospinal fluid (CSF) parameters in patients with PRES on a relatively large scale [[23], [24], [25]]. In these studies, elevated CSF protein level without CSF pleocytosis, which was called “albumino-cytologic dissociation,” was recognized as a common finding in the majority of patients with PRES. The radiographic severity of vasogenic edema positively correlated with total CSF protein levels in two of the studies [24,

Approaches to diagnosing PRES

At present, there are no diagnostic criteria for PRES, and both clinical and neuroimaging findings are often not specific. Therefore, it is important to perform a thorough differential diagnosis. As mentioned above, MRI is the key diagnostic examination when a patient presents with acute development of neurological signs and symptoms and arterial hypertension or toxic conditions. Acute hypertension is associated with most cases of PRES, but it is not necessary for the diagnosis. The most common

Conclusions

PRES is a rare condition caused by cortical-subcortical vasogenic edema visualized by typical MRI findings in the occipital and parietal lobes. The pathophysiology has not been elucidated but involves endotheliopathy of the posterior cerebral vasculature that results in failed cerebral autoregulation, posterior edema, and encephalopathy. The most common manifestations are seizures, headache, and optical impairments. PRES-associated clinical signs and symptoms and neuroimaging lesions are

Funding

None.

Authorship

All authors contributed equally to the content of this review.

Declaration of Competing Interest

We declare no competing interests.

Acknowledgments

The authors would like to thank to Enago (www.enago.jp) for English language review.

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