Type:
Educational Exhibit
Keywords:
Drugs / Reactions, Acute, Education, MR, CT, Neuroradiology brain, CNS, Hypertension
Authors:
P. Faria João, M. Bousende, T. Palma; Amadora/PT
DOI:
10.1594/ecr2013/C-0512
Background
Posterior Reversible Encephalopathy Syndrome (PRES) is a clinicoradiological entity first described by Hinchey et al.
in 1996.
Initially it was thought that it occured with a predominantely posterior distribution,
was limited to the white matter and was always reversible.
It can extend into other regions (i.e temporal or frontal lobes,
pons,
cerebellum,
cortical grey matter),
and some reports have suggested the possibility of neurological impairment or death.
The exact incidence of PRES has not been determined.
The majority of cases reported occur in midlle-aged patients,
although it has been described in the pediatric age.
There is a strong predominance of cases in women.
The pathophysiology of PRES is still a topic of debate.
The classically proposed mechanism relates the ocurrence of PRES to an hypertensive state with failure of the sympathetic-dependent system of autoregulation of perfusion pressure (which is elevated) causing vasogenic edema.
The predominantely posterior distribution of findings could be related to the less dense local degree of sympathetic innervation,
therefore becoming more susceptible to the hemodinamic stress.
The major limitation of this hypothesis is the fact that hypertension has been reported absent in up to 23% of cases.
Even when hypertension is present it may not be documented above the threshold level of autoregulation (mean arterial blood pressure >160 mmHg),
although it should be noted that in a patient with no previous history of hypertension smaller tensional increments may be enough to induce significant vasoconstrition.
In patients without hypertension the most accepted theory for the development of vasogenic edema involves a disruption of the blood-brain barrier with direct neuroendotelial damage.
The latter is the result of vasoconstriction and downstream hypoperfusion.
Several clinical conditions have been correlated with the onset of PRES.
The most frequently reported are drug toxicity (specially from chemotherapeutical agents) eclampsia/pre-eclampsia,
immunosuppressed states (mostly related to transplantation),
sepsis and autoimune diseases (e.g Wegener´s granulomatosis,
systemic lupus erythematous) among many other rarer ones.
Cinical findings are not specific.
At presentation the most common symptoms are headache,
seizures,
confusion,
vision changes,
paresis,
hemianopsia and nausea.
They can have a subacute onset or may be recognized acutely.
Laboratory findings usually reflect the basal clinical condition and are not specific for PRES.
When the underlying cause of PRES is recognized and adequately treated,
a reversal of the associated clinical and imaging findings is expected.