Histopathological features with angiographic correlates of internal carotid artery pseudo-occlusion: impact of plaque compositions

Clinical article

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Object

This study describes clinicopathological characteristics of pseudo-occlusion of the internal carotid artery with regard to its possible mechanisms.

Methods

The authors retrospectively reviewed 17 patients with pseudo-occlusion and 23 with high-grade stenosis (North American Symptomatic Carotid Endarterectomy Trial criteria ≥ 90%, but no collapsed distal internal carotid artery) who underwent carotid endarterectomy. Atherosclerotic risk factors, clinical presentation, angiographic findings, and histological features of plaque obtained from the carotid endarterectomy were investigated and comparisons were made between groups.

Results

Plaques obtained in the pseudo-occlusion group were significantly more fibrous and less atheromatous than those in the high-grade stenosis group. Old, organized thrombi were more frequently found in pseudo-occlusion group plaques than in high-grade stenosis group plaques. Plaques acquired in the pseudo-occlusion group had 2 different histological features: the presence or absence of the original lumen. The pseudo-occlusion plaques with total occlusion and recanalization (8 patients) were composed of thrombotic total occlusion with lumen recanalization by large neovascular channels, whereas those with severe stenosis (9 patients) were fibrous or fibroatheromatous and had severe stenosis of the original lumen. In patients with pseudo-occlusion and total occlusion and recanalization, the authors observed a significantly higher incidence of transient ischemic attack and anterior communicating artery–posterior communicating artery collateral flow than those with high-grade stenosis and pseudo-occlusion with severe stenosis.

Conclusions

Plaques of the pseudo-occlusion group were more fibrous than those of the high-grade stenosis group and had 2 different histological features: pseudo-occlusion with total occlusion and recanalization or pseudoocclusion with severe stenosis. This difference in plaque histology may be related to the clinical features of pseudoocclusion, such as symptoms and collateral flow patterns.

Abbreviations used in this paper: ACoA = anterior communicating artery; CEA = carotid endarterectomy; ICA = internal carotid artery; NASCET = North American Symptomatic Carotid Endarterectomy Trial; PCoA = posterior communicating artery.

Article Information

Address correspondence to: Noriyuki Sakata, M.D., Department of Pathology, Faculty of Medicine, Fukuoka University, 45-1, 7-chome Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan. email: nysakata@fukuoka-u.ac.jp.

Please include this information when citing this paper: published online May 6, 2011; DOI: 10.3171/2011.3.JNS101434.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Angiographic pseudo-occlusion criteria of the ICA. A: Severe stenosis of the ICA with a collapsed distal ICA. B: Back filling of the ipsilateral carotid siphon via the ophthalmic artery in the early arterial phase. C: Delayed antegrade flow of the patent ICA in the late arterial phase.

  • View in gallery

    Representative quantitative analysis of the atheromatous core and fibrosis in atherosclerotic plaque. A: Light microscopic image of the culprit lesion examined. B–D: Quantitative analysis using a microanalyzer program, with areas of atherosclerotic plaque, atheromatous core, and fibrosis shown in B, C, and D, respectively. Massontrichrome staining. The percentage area of atheromatous core (% atheroma) and fibrosis (% fibrosis) is calculated by the following equation: % atheroma = (C/B) × 100 (%); % fibrosis = (D/B) × 100 (%).

  • View in gallery

    Representative photomicrographs of carotid artery atherosclerotic plaques showing 3 different histopathological features associated with clinical characteristics. A and B: A patient with high-grade stenosis without narrowing of the distal ICA has a soft plaque with massive atheromatous gruel (a) covered by a thin fibrous cap (Fc). C and D: A patient with pseudo-occlusion of the original lumen (o) has a hard plaque with severe stenosis consisting mainly of fibrous tissues (f) accompanied by hemorrhage into the atheromatous gruel (h). Asterisk indicates artificial disruption. E and F: A patient with pseudo-occlusion without the original lumen has thrombotic organized total occlusion of the ICA with recanalization by neovascular channels and fibrosis (f). A small atheroma (a) is also found in the intima plaque. H & E (A, C, and E) and Masson-trichrome (B, D, and F). Bar = 2 mm (A–F).

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