The effect of carotid occlusive disease on the distribution of brain lesions in patients with systemic conditions—an example of PRES

Severe hypertension is a major cause, among a long list of recognized causative factors of posterior reversible encephalopathy (PRES). We present an interesting case of a middle-aged patient with hypertension and asymmetric distribution of PRES due to tumor-related encasement and narrowing of the right internal carotid artery and relative sparing of the ipsilateral right cerebral hemisphere. White matter lesions from PRES were mostly seen in the contralateral left cerebral hemisphere and bilateral posterior fossa. It is theorized that organs or tissues distal to a chronically constricted vessel are protected from hypertensive changes (such as PRES) as the arterial stenosis reduces the transmission of hypertension-related effects, presumably due to a combination of hypoperfusion and alterations in compensatory changes in vessel autoregulation. While protected from the effects of hypertension, the patient is, however, at risk for border-zone infarction from hypoperfusion. We believe that this case report provides a better understanding of the mechanism underlying the etiology of PRES as primarily regulated by the important baroreceptors and autoregulation mechanism of the carotid artery.