Posterior Reversible Encephalopathy Syndrome
Posterior reversible encephalopathy syndrome (PRES) is a syndrome characterized by neurotoxicity in the setting of posterior cerebral edema visualized on neuroimaging in the setting of an inciting or predisposing incident. PRES is a relevant condition to the Ophthalmologist as the neurotoxicity is often manifest as visual disturbances such as loss of vision, blurry vision, scotoma, and visual hallucination. Other neurotoxic manifestations include headache, aphasia, facial numbness, seizure, and ataxia.
The neurotoxic manifestations are thought to result from cerebral edema. The edema is typically in the parieto-occipital lobes and occurs in a watershed pattern. Edema can also be present in the frontal lobes, brainstem, cerebellum, and spinal cord.
A variety of conditions can predispose to PRES. The most common conditions include toxemia of pregnancy (eclampsia and preeclampsia), posttransplantation after allogenic bone marrow transplant or solid organ transplant, immunosuppresion with cyclosporine or tacrolimus, systemic inflammatory response syndrome, mulitorgan dysfunction syndrome, and autoimmune conditions such as systemic lupus erythematosis, scleroderma, Wegener’s granulomatosis, and polyarteritis nodosa. PRES can also occur after chemotherapy, usually in high doses, with cytarabine, cisplatin, gemcitabine, tiazofurin, bevacizumab, and kinase inhibitor BAY 34-9006. Additionally, case reports exist of PRES occurring in the setting of hypomagnesemia, hypercalcemia, hypocholesterolemia, intravenous immunoglobulin treatment for Guillen-Barre syndrome, ephedra overdose, and tumor lysis syndrome.
Two theories exist for the pathogenesis of PRES. The first suggests hypertension causes a failure of cerebral autoregulation causing an injury to the capillary network and thus hyperperfusion causing a vasogenic cerebral edema. The other theory suggests endothelial dysfunction causing vasoconstriction and then hypoperfusion causing ischemia and then vasogenic cerebral edema. Both theories acknowledge a role in the breakdown of the blood-brain barrier causing vasogenic cerebral edema, which is evident on neuroimaging.
Neuroimaging such as CT and MRI are utilized to discern cerebral edema. Advanced neuroimaging such as catheter angiogram, MRA with 3D time of flight, Tc99m SPECT, and rCBV can be utilized. Clinical suspicion, with attention to predisposing factors, along with neuroimaging evidence of cerebral edema are sufficient for diagnosis.
A general examination, with attention to vital signs, and full neurologic examination should be performed. A full ophthalmic exam should be performed to evaluate for any potential other causes of visual complaints. Formal Goldmann visual field testing should be strongly considered to evaluate for any scotoma.
Visual symptoms can range from loss of vision as severe as NLP. Additional symptoms include scotoma, blurry vision, and visual hallucinations.
Laboratory tests can help as needed to identify any predisposing or inciting factors.
The management of PRES requires a multidisciplinary role. The ophthalmologist should continue to follow the patient to ensure resolution of visual manifestations. A neurologist is vital in both initial evaluation and management, especially with seizure prophylaxis. Additional specialists, such as obstetricians, rheumatologists, oncologists, are needed to assist with individualized management of the inciting factors. An internist is vital to management of blood pressure, as many patients will require intravenous medications for appropriate control. Definitive treatment and follow up is aimed at treatment of the inciting factors. Neuroradiology can assist in the monitoring of neuroimages with interpretation of advanced imaging as needed.
PRES itself carries a relatively good prognosis with partial to complete resolution of neuroimaging abnormalities and partial to complete resolution of visual manifestations. The overall prognosis of the patient is individualized and based upon the inciting factor.
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