On the anatomical definition of arterial networks in blood flow simulations: comparison of detailed and simplified models.

The goal of this work is to assess the impact of vascular anatomy definition degree in the predictions of blood flow models of the arterial network. To this end, results obtained with an anatomically detailed network containing over 2000 vessels are systematically compared with those obtained with an anatomically simplified network containing the main 86 vessels, the latter being a truncated version of the former one. The comparison is performed quantitatively and qualitatively in terms of pressure and flow rate waveforms, wave intensity analysis and impedance analysis. Comparisons are performed under physiological conditions and for the case of common carotid artery occlusion. Mechanisms of blood flow delivery to the brain, as well as different blood flow steal phenomena, are unveiled in light of model predictions. Results show that detailed and simplified models are in reasonable agreement regarding the hemodynamics in larger vessels and in healthy scenarios. The anatomically detailed arterial network features improved predictive capabilities at peripheral vessels. Moreover, discrepancies between models are substantially accentuated in the case of anatomical variations or abnormal hemodynamic conditions. We conclude that physiologically meaningful agreement between models is obtained for normal hemodynamic conditions. This agreement rapidly deteriorates for abnormal blood flow conditions such as those caused by total arterial occlusion. Differences are even larger when modifications of the vascular anatomy are considered. This rational comparison allows us to gain insight into the need for anatomically detailed arterial networks when addressing complex hemodynamic interactions.

Morphological aspects of the distal medial striated artery (artery of Heubner)

The distal medial striated artery, one of the branches of the anterior complex of the circle of Willis, is important because it supplies the caudate nucleus and adjoining putamen, part of the septal nucleus and fibers of the anterior part of the internal capsule. This vessel situated in a region often dealt with in neurological surgeries and can be injured because of its anatomical relationship with important structures in this region. In this study, we examined the anatomical arrangement in 50 human brains fixed in 20 per cent formaldehyde solution. The origin of this vessel was assessed relative to the pre-, post- and communicating segments of the anterior cerebral artery. Of the 121 arteries found, 49.6 per cent arose from the post-communicating segment and were duplicated in 50.4 per cent of the cases, single in 49.6 per cent and symmetrical in 44.5 per cent. The distal medial striated artery was absent in only one specimen. In relation to the pre-communicating segment, the course of this artery was anterior in 77 per cent of the cases, superior in 20 per cent and posterior in 3 per cent. A division of the anterior perforated substance into anterior, lateral and medial regions served to locate the terminal branches of the artery. The terminal branches penetrated the anterior, lateral and medial regions in 48.8 per cent, 47 per cent and 4.3 per cent of the cases respectively.

Omental transplantation for Alzheimer's disease.

The acetylcholine, dopamine, serotonin and other neurotransmitters may be reduced in the subcommissural regions even in the early stages of Alzheimer's disease(AD), due to hypoperfusion of the anterior perforating and anterior choroidal arteries. This hypothesis was confirmed after the transplant of omental tissue on the optic chiasma, carotid crotch and anterior perforated space in a woman with moderate AD. Neurological improvement was better in the first week after the surgery than in the following months.