Cholesterol crystal embolization in rat brain: a model for atheroembolic cerebral infarction

Acute and delayed effects of embolizing cerebral surface vessels with cholesterol crystals were studied by direct observation in anesthetized rats and rabbits, using an open-skull technique, and by histological examination of brains at intervals of one day and one week following embolization. The number and size spectrum of crystals, which were infused into the ipsilateral internal carotid artery, were believed to approximate those released by a rupturing large atheromatous plaque in man, but the other lipid materials contained in such plaques were intentionally excluded. It was found that cholesterol crystals had only limited ability to impede blood flow in the 20--80 mu diameter arteries in view. They were also inert within the lumen, causing no vessel wall reaction even after a week; nor was any evidence seen of a thrombogenic effect. Local caliber changes in the containing artery were reproducibly seen, with dilatation of the arterial segment proximal to the embolus and narrowing of the segment in front. These changes appeared to represent an active response of the vessel wall, rather than a passive response to alterations in intraluminal pressure. The difficulty in subsequently locating cholesterol emboli histologically was confirmed. Possible therapeutic implications for atheroembolic cerebral infarction in man were discussed.