[Rheological study on the development and growth of cerebral aneurysms using an experimental animal model].
To clarify the pathogenesis of saccular cerebral aneurysms, it is essential to study hemodynamic influences on the development and growth of these aneurysms. Up to now, a number of experimental flow studies have been done using a variety of glass models of cerebral arterial bifurcations with or without aneurysms. Blood flow at the bifurcation can be readily influenced even by subtle changes of the intraluminal geometry. But, it is quite difficult to obtain the accurate geometry of the lumen artificially. Using the bifurcation of animal model of the disease, this limitation can be overcome. In the present study, using cerebral arterial bifurcations in rats which were treated to induce experimental cerebral aneurysms, flow patterns were studied to elucidate the pathogenesis of cerebral aneurysms from the rheological point of view. (Experiment-1) Microscopic flow visualization at the bifurcation of major cerebral arteries in control rats was done. After perfusion and fixation, a right anterior cerebral and olfactory artery (ACA/OA) junction was extirpated from the base of the brain and served for laboratory preparation. A suspension of small latex particles in various sizes was subjected to constant flow rate through the preparation, recorded on videotapes and 16 mm cinefilms. The results of flow analysis were: 1) Small particles accumulated at the region just distal to the apical intimal pad on the side of daughter ACA, where the initial changes of aneurysm formation are known to occur. This finding indicates a flow stagnation. 2) The apical intimal pad, not the apex itself, acted as the flow divider. 3) Flow disturbances existed both in the daughter ACA and in the OA. (Experiment-2) Using ACA/OA bifurcations with shallow invaginations and small aneurysms, which were obtained from the rats treated to induce experimental aneurysms, flow patterns were obtained by the same methods as mentioned in (Experiment-1). Flow characteristics were: 1) Particles entering the dome from the proximal end of the aneurysmal orifice markedly decreased their flow velocity at that site. 2) Particles running along the luminal surface of the dome were in low flow velocity. This indicates a tendency of stagnation there. 3) The wall shear stress was highest at the distal end of the aneurysmal orifice, which may be responsible for the development of these lesions. (Experiment-3) A technique was developed to visualize the flow at the major cerebral arterial bifurcation in living rats which were prepared to induce experimental cerebral aneurysms.(ABSTRACT TRUNCATED AT 400 WORDS)
Nakatani
H
H
Department of Neurosurgery, Kyoto University Medical School and Hospital, Japan.
D000818:Animals; D002536:Cerebral Arteries / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D066298:In Vitro Techniques; D002532:Intracranial Aneurysm / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow; D012212:Rheology