Updated on 24/01/2024
Posterior reversible encephalopathy syndrome (PRES) is an acute or subacute cerebral syndrome whose main symptoms are headache, encephalopathy, seizures or visual disturbances. This disorder is typically seen in patients with acute, severe hypertension or moderate but sudden increases in blood pressure. Other common causes are chemotherapeutic and immunosuppressive drugs and toxic substances. The most common neuroimaging finding is vasogenic oedema with white matter hyperintensity in the occipital and sometimes adjacent parietal lobes. When PRES is recognized promptly and the underlying cause is treated, most patients recover.
The incidence is 3 per 100,000 people. Case series show that PRES is seen in all age groups, with the highest incidence among young and middle-aged adults, and is more common in women than men. It is twice as common in women as in men.
The most prominent typical feature of PRES is an encephalopathy that can range from mild confusion to coma seen in 94% of patients. In half of the cases, headache develops gradually, but sometimes there may be sudden thunderclap headache. Epileptic seizures occur in about three-quarters of patients during the disease. Seizures are only rarely an initial feature and may progress to unstoppable seizures (status epilepticus) in up to 18% of patients. Visual disturbances are present in 20-39% of patients.
Magnetic resonance imaging (MRI) is the most important diagnostic tool. MRI shows vasogenic oedema in the white matter, mostly bilateral and typically in the posterior lobes of the brain (occipital). However, unilateral lesions or grey matter involvement may also be seen.
The differential diagnosis of PRES includes cerebral infarction, especially posterior circulation or end zone strokes, central nervous system (CNS) infections, demyelinating diseases, brain cancers, dural venous sinus thrombosis, CNS vasculitis, toxic encephalopathies and mitochondrial diseases. Some cerebrovascular dysregulation syndromes, especially reversible cerebral vasoconstriction syndrome with irregular segments of cerebral vasoconstriction, may overlap with PRES.
With prompt control of the triggering cause of PRES and supportive care, it is possible to achieve good results. Most case series show that PRES is usually benign. In many cases, PRES resolves completely within days to weeks after the triggering factor is removed and blood pressure is controlled. Radiological improvement lags clinical improvement. However, death and permanent severe neurological disability have also been reported. Death can occur from progressive brain oedema, intracerebral haemorrhage or as a complication of the underlying condition.
