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Posterior Reversible Leukoencephalopathy (PRES)
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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
Covarrubias DJ, Luetmer PH, Campeau NG. Posterior reversible encephalopathy syndrome: prognostic utility of quantitative diffusion-weighted MR images. AJNR Am J Neuroradiol 2002; 23:1038.
Fugate JE, Rabinstein AA. Posterior reversible encephalopathy syndrome: clinical and radiological manifestations, pathophysiology, and outstanding questions. Lancet Neurol 2015;14(9):914–925.
Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med 1996; 334:494.
Paulson OB, Strandgaard S, Edvinsson L. Cerebral autoregulation. Cerebrovasc Brain Metab Rev 1990; 2:161.
Roth C, Ferbert A. Posterior reversible encephalopathy syndrome: long-term follow-up. J Neurol Neurosurg Psychiatry 2010; 81:773.
Schwartz RB, Mulkern RV, Gudbjartsson H, Jolesz F. Diffusion-weighted MR imaging in hypertensive encephalopathy: clues to pathogenesis. AJNR Am J Neuroradiol 1998; 19:859.

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