1. Department of Neurosurgery, Tokyo Rosai Hospital, 4-13-21 Omori-minami, Ota-city, Tokyo 143-0013, Japan;
2. Department of Neurosurgery, Blue-sky Matsui Hospital, 739 Muraguro-cho, Kanonji-shi, Kagawa-ken 768-0013, Japan;
3. Department of Neurosurgery, Narita Tomisato Tokusyukai Hospital, 1-1-1 Hiyoshidai, Tomisato-shi, Chiba-ken 286-0201, Japan;
4. Department of Neurosurgery, Koshigaya Neurosurgical Clinic, 5-7 Gamoukotobuki-cho, Koshigaya-shi, Saitama-ken 343-0836, Japan
Hemodynamic consideration of intracranial aneurysm
1. Department of Neurosurgery, Tokyo Rosai Hospital, 4-13-21 Omori-minami, Ota-city, Tokyo 143-0013, Japan;
2. Department of Neurosurgery, Blue-sky Matsui Hospital, 739 Muraguro-cho, Kanonji-shi, Kagawa-ken 768-0013, Japan;
3. Department of Neurosurgery, Narita Tomisato Tokusyukai Hospital, 1-1-1 Hiyoshidai, Tomisato-shi, Chiba-ken 286-0201, Japan;
4. Department of Neurosurgery, Koshigaya Neurosurgical Clinic, 5-7 Gamoukotobuki-cho, Koshigaya-shi, Saitama-ken 343-0836, Japan
摘要 We reviewed basic considerations in fluid dynamics of cerebral aneurysms and applied these in surgery on the three most common types: internal carotid-posterior communicating artery, middle cerebral artery, and anterior communicating artery. It was found that aneurysmal initiation and growth do not occur at symmetric bifurcations. As blood flow always obeys the law of inertia, jet flow into the aneurysm will disperse along the wall; assuming the aneurysmal wall strength is even, the shape of the aneurysm becomes round or oval. When neurosurgeons encounter an aneurysm that is not round or oval, the wall may be fragile and requires great care during surgical manipulation.
Abstract: We reviewed basic considerations in fluid dynamics of cerebral aneurysms and applied these in surgery on the three most common types: internal carotid-posterior communicating artery, middle cerebral artery, and anterior communicating artery. It was found that aneurysmal initiation and growth do not occur at symmetric bifurcations. As blood flow always obeys the law of inertia, jet flow into the aneurysm will disperse along the wall; assuming the aneurysmal wall strength is even, the shape of the aneurysm becomes round or oval. When neurosurgeons encounter an aneurysm that is not round or oval, the wall may be fragile and requires great care during surgical manipulation.
20180119184743 Figure 1 Schema of asymmetric bifurcation. Main blood flow impinges the bifurcation apex, creating a stagnation point; accelerating flow enters the smaller branch. Flow separation occurs at the lateral wall of the main vessel.
20180119184750 Figure 2 Two branch types. Left side: when one of the split-out branches is extremely small, the other is nearly a right angle. Right: When the vessel divides into nearly symmetric branches, the split-out branches make almost equal angles.
20180119184800 Figure 3 Blood flow creates a jet through the small inlet zone in the systolic phase, causing whirling flow along the aneurysmal wall, with decreased velocity; outflow occurs through the opposite side of the orifice during the diastolic phase.
20180119184807 Figure 4 Cerebral angiography showing a saccular aneurysm at the sphenoid wing and the aneurysmal dome buried in the temporal lobe.
20180119184816 Figure 5 Symmetric bifurcation (upper schema) creating symmetric parabolic blood flow, with little blood entering the aneurysm because of the small difference in flow velocity at the orifice. Asymmetric bifurcation induces an asymmetric flow profile (lower schema), creating a pressure difference at the aneurysmal orifice and causing flow into the aneurysm.
20180119184825 Figure 6 When a pressure difference between bilateral ICA systems is present, blood flow enters from the opposite ACA into the ACoA.
20180119184834 Figure 7 Photo of stream-line in an A1-A2 junctional aneurysm model. The A1-A2 junction, where the ACoA branches. Increased shear stress leads to an aneurysm-like bulge on the vessel wall. This bulge eventually becomes an aneurysm.
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2017, Vol. 3 
