Although the clinical picture is not specific, an early MRI is usually diagnostic 1 , 3. Brain imaging usually reveals vasogenic oedema in the parieto-occipital regions of both cerebral hemispheres 3. There is no specific treatment, but the disorder usually resolves when the underlying cause is removed 2.
Seizures should be treated in the normal manner 1 , 2 , however, the length of treatment is debated 2. The general consensus is that blood pressure BP should be lowered in patients with hypertension. Pronounced fluctuations in BP should be avoided and therefore intravenous IV infusion of nitroprusside or nicardapine has generally been used 1 , 2 , 4.
Any medicines suspected of causing PRES should be discontinued 2. In most cases of PRES, symptoms typically improve within one week. Neuroimaging resolution normally takes longer 4. Recently the PRES early warning scoring PEWS scale which consisted of 1 risk factors, 2 clinical features and 3 EEG features has improved the prediction of PRES early in suspected cases, with a high index of suspicion in patients with a score of 10 points or higher 65 , Besides, there is enhancement in the subacute phase on follow up post contrast MRI.
Differentiating tumor from PRES is based on time frame of symptom involvement and lack of resolution on follow up imaging. Hypoxic ischemic encephalopathy can be differentiated by the history, gyriform pattern of restricted diffusion predominantly involving the cortex and lack of resolution on follow up imaging.
Infectious encephalitis especially rhombencephalitis may be made by clinical history and clinical examination. Reversible cerebral vasoconstriction syndrome may be differentiated by classic thunderclap headache in the presence of known triggers and vasoconstriction of the vessels.
In certain cases, this may coexist with PRES. Acute hepatic encephalopathy is differentiated by the history of chronic liver disease, hyperintensity on FLAIR with possibly restricted diffusion in both thalami, posterior limb of internal capsule and periventricular white matter. Management is primarily supportive and guided by expert consensus. Prompt recognition is the key as timely removal of the precipitating factor is important to achieve favorable outcomes 1 , 7.
Currently there are no randomized trials on various interventions have been conducted in these patients. Common indications for transfer to the ICU include encephalopathy, seizures, and status epilepticus The following steps should be performed 1 , 52 :.
Removal or reduction of the triggering factor withdrawal of cancer chemotherapy or immunosuppressive agents. In patients with PRES related to cancer chemotherapy or immunosuppressive agents, long term management of immunosuppressive agents and chemotherapy remains a challenging issue and should be individualized. Supportive care with hydration, correction of electrolyte disturbances.
Monitoring of airway and ventilation. Intubation may be required in patients with altered mental status. In pregnant women, prompt delivery should be considered. In patients with renal failure, prompt dialysis should be performed. The goal is to maintain mean arterial pressure between and mm Hg. Intravenous agents are preferred to avoid fluctuations of blood pressure and the choice of agents is left to the discretion of the physician.
Continuous infusions are frequently required to avoid fluctuations of blood pressure and achieve the goal blood pressure. First line agents include nicardipine, labetalol, nimodipine, and second line agents include sodium nitroprusside, hydralazine, and diazoxide. Avoid angiotensin converting enzyme inhibitors in pregnant women. In patients subarachnoid hemorrhage with PRES from induced hypertension for vasospasm gradual reduction of blood pressure is crucial for neurological improvement Intravenous anticonvulsants first line with diazepam, second line with forphenytoin, phenobarbital.
In refractory cases propofol, pentobarbital, midazolam may be used. Continuous EEG monitoring may be considered. In pregnant women, magnesium sulfate is indicated to prevent seizures. It has cerebral vasodilatory effects and reduces blood vessel permeability. Although seizures are common long-term data on risk of recurrent seizures and epilepsy is limited due to lack of large population based studies.
Currently, there are no standard guidelines for management of PRES related seizures and treatment with antiepileptic agents must be made based on individual basis. Antiepileptic drugs are frequently prescribed to patients with seizures. As epilepsy is rare long-term antiepileptic medications are not warranted in majority of these patients.
There is often a dilemma on the optimal duration of antiepileptics. The most common antiepileptics that have been used during hospitalization include benzodiazepines, levetiracetam and phenytoin and upon discharge levetiracetam and phenytoin, with majority of them on a single agent.
Since seizures are uncommon out of the acute phase, antiepileptic agents may be quickly tapered. In a single center study, the median duration of antiepileptic agents was 3 months IQR 2—7 months.
The overall prognosis of both generalized and focal seizures in PRES is benign. Besides, not all patients with seizures have been treated with antiepileptic agents and none of these patients developed recurrent seizures 31 , It is unclear if antiepileptic agents play a role on the risk of subsequent seizures and epilepsy in these patients. If antiepileptic agents are started, discontinuation following resolution of PRES should be considered, once there is adequate control of risk factors, and absence of factors that might substantially lower the seizure threshold.
It is not uncommon for patients to have recurrent episodes of PRES from recurrence of risk factors like sickle cell crisis, autoimmune conditions, hypertensive crisis, renal failure, and multiorgan failure. Management of malignant PRES requires aggressive supportive care. Various interventions that have been undertaken in patients with raised ICP include osmotherapy, draining of cerebrospinal fluid by external ventricular drain, craniectomy and evacuation of hematoma.
All patients achieved favorable functional outcomes based on the mRS modified Rankin Score of 1—2 on long term follow up In patients with acute obstructive hydrocephalus, an external ventricular drain placement may be required for management Certain deficits that require long-term care include epilepsy and motor deficits.
PRES is an acute neurotoxic syndrome and the prognosis is highly dependent on the etiological factor. Studies have reported that patients with preeclampsia-eclampsia have less severe cerebral edema, hemorrhage, contrast enhancement with a tendency for complete resolution on imaging and good functional outcome 10 , Other factors that have been associated with poor outcome include severe encephalopathy, hypertensive etiology, hyperglycemia, neoplastic etiology, longer time to control the causative factor, the presence of multiple comorbidities, elevated CRP, low CSF glucose, and coagulopathy 9 , 10 , 47 , Various imaging features that are associated with poor outcome include corpus callosum involvement, extensive cerebral edema or worsening imaging severity, hemorrhage, subarachnoid hemorrhage, and restrictive diffusion on imaging 47 , 60 , 76 — The type, location and severity of hemorrhage that is associated with poor outcome are inconsistent across various studies 47 , 76 , While small hemorrhages do not have an impact on outcome, multiple or massive hemorrhages might be associated with poor outcome.
Several studies have demonstrated correlation between the degree of hypertension with clinical outcome and severity of edema on imaging. Interestingly, while the severity of edema on MRI correlated with clinical outcomes, the presence or patterns of gadolinium based contrast enhancement did not correlate with functional outcomes To summarize, although there are several associations, identifying a single predictor of outcome has been challenging in these patients.
Recent data from animal studies have demonstrated blood brain barrier disruption as a possible mechanism for development of vasogenic cerebral edema from acute hypertension and thus may be a target of future intervention Currently, there is paucity of data on its clinical implications in PRES.
Currently, the available data on outcomes are from single institutions with paucity of data from long-term epidemiological studies.
Its heterogeneous nature limits its ability to generalize. PRES has a favorable prognosis in general, but fatalities can occur. A standardized algorithm that incorporates the clinical, etiological, serological markers, imaging features with various comorbidities and will assist in future studies.
Various pathophysiological mechanisms need to be explored at bench side to determine reliable laboratory and imaging markers and therapeutic interventions in order to improve functional outcomes are warranted. The author confirms being the sole contributor of this work and has approved it for publication. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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