Acute cortical blindness due to posterior reversible encephalopathy.

An acutely hypertensive 55 year-old male experienced seizures and cortical blindness post-operatively. CT scans demonstrated hypointensities in the occipital lobes bilaterally. MRI revealed symmetrical bilateral hyperintense signals in the same region, involving both grey and white matter. Thromboembolic screening investigations including vertebral artery doppler studies were normal and echocardiography demonstrated borderline left ventricular hypertrophy. A diagnosis of posterior reversible encephalopathy syndrome (PRES) was reached and there was complete resolution of blindness with antihypertensive therapy. This case supports the vasogenic theory of PRES which suggests that sustained high grade fluctuations in blood pressure lead to a reduction in cerebral vascular autoregulatory function. The resultant failure of compensatory vasoconstriction to prevent hyperperfusion causes fluid to extravasate into the occipital lobes, which in the present case resulted in cortical blindness.