Recently occluded intracranial and extracranial carotid arteries - Relevance of the unstable atherosclerotic plaque

Background and Purpose-It is now widely accepted that thrombotic coronary a rtery occlusion usually follows rupture of an unstable atherosclerotic plaq ue. The significance of such instability in arteries supplying the brain is less well appreciated. We therefore describe the clinical and pathological features of recent, symptomatic internal carotid artery occlusion to exami ne the pathogenetic role of plaque instability at both extracranial and int racranial sites, Methods-Cases were selected from a consecutive series of 188 adult neuropat hology autopsies. In 90 of these, the principal neuropathological abnormali ty was cerebral infarction, in 14 cases due to recent occlusion of 1 or mor e segments of the internal carotid artery. In each case, a full systemic, c ardiovascular, and neuropathological autopsy was performed. Plaque instabil ity was assessed by the presence or absence of a large, necrotic, lipid cor e; a thin, fibrous cap; and superficial inflammation. Results-Of the 14 cases, 3 showed extracranial (carotid sinus), 7 intracran ial, and 4 both extracranial and intracranial carotid artery occlusion. In 6 of the 7 occluded carotid sinuses, thrombus overlay an ulcerated, unstabl e, atherosclerotic plaque. In 1 extracranial and all II intracranial occlus ions there was either no atheroma or a mildly stenotic, stable, fibrous pla que, and in these cases, the cause of occlusion was embolism (8 cases), gia nt-cell arteritis (1 case), and unknown (3 cases). Conclusions-Coronary-type rupture of an unstable atherosclerotic plaque is the usual cause of fatal occlusion of the carotid sinus, but other causes u sually underlie intracranial carotid occlusion. The nature and consequences of intracranial atherosclerosis require further study.