Published: 2 March 2017
Prescriber Update 38(1): 5-6
Posterior reversible (leuko) encephalopathy syndrome (PRES) is a clinico-radiological syndrome that is increasingly being recognised as a side effect of medicines1,2. The syndrome refers to a disorder of reversible subcortical vasogenic brain oedema in patients with acute neurological symptoms.
PRES was first described in the 1990s3. The incidence is generally unknown. For patients undergoing organ or stem cell transplant the reported incidence ranges from 1% to 10% in both adults and children4. PRES is slightly more common in women1.
PRES is often associated with conditions such as hypertension (53% of reported cases), kidney disease (45%), malignancy (32%), dialysis dependency (21%), transplantation (24%), autoimmune disorders (11%) and eclampsia (11%)1.
The time between starting a medicine and the onset of PRES has not been well described. For medicines used in solid organ transplant, onset times may be over a year and may be associated with episodes of graft versus host disease or infection4.
The pathophysiology of PRES is unclear but is thought to be partially due to increased blood pressure2.
The most common clinical signs and symptoms are1:
The onset of symptoms is usually rapid, reaching a peak in 12 to 48 hours4.
Diagnosis is difficult, and clinical context and clinical judgement are essential. Differential diagnoses include encephalitis, malignancy, reversible cerebral vasoconstriction syndrome, stroke, progressive multifocal leukoencephalopathy and vasculitis. Although the clinical picture is not specific, an early MRI is usually diagnostic1,3. Brain imaging usually reveals vasogenic oedema in the parieto-occipital regions of both cerebral hemispheres3.
There is no specific treatment, but the disorder usually resolves when the underlying cause is removed2. Seizures should be treated in the normal manner1,2, however, the length of treatment is debated2. The general consensus is that blood pressure (BP) should be lowered in patients with hypertension. Experts recommend that BP is reduced by 25% in the first few hours1,2,4. Pronounced fluctuations in BP should be avoided and therefore intravenous (IV) infusion of nitroprusside or nicardapine has generally been used1,2,4. Any medicines suspected of causing PRES should be discontinued2.
In most cases of PRES, symptoms typically improve within one week. Neuroimaging resolution normally takes longer4.
However, cerebral haemorrhage or ischaemia can occur. Irreversible neurological defects have been reported in 10% to 20% of cases and death in 3% to 6% of cases1,2. PRES may recur in 5% to 10% of cases, more commonly in patients with uncontrolled hypertension.
The Centre for Adverse Reactions Monitoring (CARM) has received three reports of PRES.
Please continue to report any adverse reactions to CARM. Reports can be submitted on paper or electronically (https://nzphvc.otago.ac.nz/).