Intracranial atherosclerotic disease associated with moyamoya collateral formation: histopathological findings

Abstract

Atherosclerotic disease has been suspected as a cause of moyamoya disease in some patients but has not, to the authors' knowledge, been confirmed by pathological studies. The authors present the histopathological findings in a patient with moyamoya collateral formation associated with atherosclerotic occlusive disease of the distal internal carotid artery (ICA). Typical atheromatous changes were evident in the distal ICA and proximal middle cerebral artery. In addition, intimal thickening, fibrosis, and abnormal internal elastic lamina were present in these vessels. These findings are common in moyamoya but not in atherosclerotic disease. Proliferation and enlargement of the lenticulostriate arteries in the basal ganglia was also identified. Moyamoya phenomenon secondary to atherosclerotic disease has similar histopathological features to idiopathic moyamoya phenomenon, both in the affected large basal arteries and lenticulostriate collaterals. These findings support the hypothesis advanced by Peerless that moyamoya is a 2-step process involving an obliterative vasculopathy of the terminal ICA and a secondary proliferative response.

Figures

Fig. 1

Anterior projection cerebral angiogram obtained after left common carotid injection showing occlusion of distal ICA and extensive moyamoya collateral formation.

Fig. 2

Photographs of the circle of Willis at autopsy. Only a short, markedly attenuated A1 ACA segment was seen on the right (arrow), whereas the left A1 segment had 2 major branches (A). At closer inspection, the left MCA (B) shows increased branching beyond that of the usual trifurcation, whereas both the left and right MCAs (C) demonstrate extensive yellow-white atheromatous deposits proximally. Small vascular branches are seen coming off the main trunks in both MCAs as well as other large arteries. BA = basilar artery; VA = vertebral artery.

Fig. 3

Photomicrographs of sections from the left ACA revealing foci of luminal narrowing with complete occlusion focally (arrows, A and D). At higher magnification, cholesterol-rich atheromatous plaques (arrow, B) and partially recanalized thrombi (C) were seen. Foci of intimal fibrosis and distortion/reduplication of the IEL were highlighted on trichrome- (E) and Verhoeff-van Gieson– (F) stained sections, respectively. H & E (A–C), trichrome (D and E), and Verhoeff-van Gieson (F). Original magnification ×1 (A and D), ×100 (B and C), and ×200 (E and F).

Fig. 4

Photomicrographs of sections obtained at autopsy. Changes in the left MCA (A and B) and right PCA (C and D) showed similar features. These included marked atherosclerotic changes and intimal thickening at vascular branch points (A) and innumerable small-caliber collateral branches (B) adjacent to the main artery (left side of image in panel B), probably representing the histological correlate of the “puff of smoke” sign often encountered on angiography. Patchy foci of marked intimal thickening and luminal narrowing were also noted (C), along with cholesterol-rich atheromatous material (arrow, D). H & E (A and C), smooth-muscle actin immunostain (B), and trichrome (D). Original magnification ×100 (A and B), ×40 (C), and ×400 (D).

Fig. 5

Photomicrographs of sections from the basal ganglia and thalamus revealing acute eosinophilic neuronal necrosis (A), scattered arterioles with lipid-rich deposition (B), and arterioles giving rise to multiple small-caliber collateral vessels (C). H & E; original magnification ×200 (A) and ×400 (B and C).