Posterior Reversible Leukoencephalopathy (PRES)
Basic Pathophysiology
- Autoregulation breaks down and excessive cerebral blood flow occurs.
- Autoregulation normally maintains constant cerebral blood flow over a wide range of systemic blood pressure.
- When the limits of cerebral autoregulation are exceeded at a rapid rate, hyperperfusion promotes extravasation of fluid into the brain parenchyma.
- There is an important overlap in the pathophysiology with reversible cerebral vasoconstriction syndrome (RVCS) ("Call-Fleming syndrome) to consider.
- The most worrisome (albeit rare) consequence is cerebral ischemia from reactive focal vasoconstriction or compression of microcirculation from the mass effect of vasogenic edema.
- Endothelial dysfunction is also implicated in the generation of vasogenic edema from blood-brain barrier disruption, especially in the setting of preeclampsia or cytotoxic therapies.
- The cerebral white matter is less dense than the cerebral cortex and thus is more susceptible to cerebral edema.
Clinical Presentation
- Confusion
- Seizures
- Headaches
- Visual field deficits (posterior predilection of the swelling)
Radiographic Findings
- Cerebral edema
- Intracerebral (intraparenchymal) hemorrhage.
Localization
- Commonly involves the cerebellum and brainstem and parietooccipital regions with sparing of the calcarine and paramedian occipital lobes.
- Distribution extends beyond a single vascular territory.
- Posterior circulation is particularly predisposed to impaired autoregulation, thus the disorder is referred to as "posterior reversible encephalopathy syndrome (PRES)".
Common causes of PRES
- Acute (rapid) hypertension
- Eclampsia
- Chemotherapies
- Cyclosporine
- Cisplatin
- Immunosuppressive agents
- Methotrexate
- Rituximab
- Renal failure
- Uremia and proteinuria
- Electrolyte abnormalities
- Hyponatremia
- Hypomagnesemia
- Eclampsia
- Vasculitis
- Systemic Lupus Erythematosis
- Blood transfusion
- Contrast Dye
Basic Management
- Reduction in blood pressure by 10-25% in the first 24 hours, followed by further reduction in the following days as clinically appropriate.
References