Someone with PRES may experience headaches, changes in vision, and seizures, with some developing other neurological symptoms such as confusion or weakness of one or more limbs.
The name of the condition includes the word "posterior" because it predominantly, though not exclusively, affects the back of the brain (the parietal and occipital lobes).
[2] Causes that may contribute to the development of PRES are: immunosuppression (especially for organ transplantation, e.g. with tacrolimus), severe infection and/or sepsis, chemotherapy, autoimmune disease, and pre-eclampsia.
[3] The following autoimmune conditions have been found to be associated with PRES: thrombotic thrombocytopenic purpura (TTP), primary sclerosing cholangitis (PSC), rheumatoid arthritis (RA), Sjögren syndrome, polyarteritis nodosa (PAN), systemic sclerosis, systemic lupus erythematosus (SLE), granulomatosis with polyangiitis (GPA), Crohn's disease and neuromyelitis optica (NMO),[1] as well as hemolytic-uremic syndrome (HUS).
[5] The precise mechanism of PRES is not fully understood, it is considered to be related to a problem with the blood vessels of the brain.
There are several theories as to why these blood vessels may become inappropriately permeable and allow the surrounding brain tissue to become swollen.
[1][5] There are no formal diagnostic criteria for PRES, but it has been proposed that PRES can be diagnosed if someone has developed acute neurological symptoms (seizure, altered mental state, headache, visual disturbances) together with one or more known risk factors, typical appearance on brain imaging (or normal imaging), and no other alternative diagnosis.
[4][5] If lumbar puncture is performed this may show increased protein levels but no white blood cells.
[1][3][4] Computed tomography scanning may be performed in the first instance; this may show low density white matter areas in the posterior lobes.
The findings most characteristic for PRES are symmetrical hyperintensities on T2-weighed imaging in the parietal and occipital lobes; this pattern is present in more than half of all cases.
[4] In many cases there is evidence of constriction of the blood vessels (if angiography is performed), suggesting a possible overlap with reversible cerebral vasoconstriction syndrome (RCVS).
Diffusion MRI may be used to identify areas of cytotoxic edema caused by poor blood flow (ischemia) but it is not clear if this prognostically relevant.
[1][5] 40% of all people with PRES are unwell enough to require intensive care unit admission for close observation and treatment of complications.
[2][1] However, in those with PRES due to pre-eclampsia or eclampsia, IV magnesium sulfate is the preferred medication for both seizures and hypertension.
[1][4][5] The incidence of PRES in certain subgroups has been estimated to be approximately 0.8% in those with end stage renal disease, 0.7% in those with SLE, and 0.5% in those with a solid organ transplant.
[7] PRES was first described in 1996 in a group of 15 patients identified retrospectively in the records of the New England Medical Center in Boston and Hôpital Sainte Anne in Paris.