Secondary histomorphological changes in cerebral arteries of normotensive and hypertensive rats following a carotid-jugular fistula induction.

Haemodynamic changes in cerebral circulation are associated with the natural ageing process and associated pathology, leading to the development of incapacitating neurological and neurovascular diseases. Due to inherent biological limitations, current literatures mostly aimed at studying the correlation descriptively or quantifying the relationship in vitro or using computational models. In this paper, a model of a carotid-jugular fistula in the rat was used to create a haemodynamic insult to the intracranial arterial circulation and subsequent venous drainage. An arterial-venous (AV) fistula was created in 12 rats, 6 of which are normotensive Wistar-Kyoto strain (WKY) and the rest spontaneously hypertensive strain (SHR) with an additional 6 in each strains designed as controls without previous surgery. After 4 weeks of convalescence, all 24 rats were euthanised and their cerebral circulation was examined histomorphologically. We confirmed an intrinsic morphological difference between normotensive WKY and hypertensive SHR and found a modest but significant arterial shrinkage in both strains induced with AV fistula. We also reported that alterations in blood flow are also associated with marked extracellular matrix changes. We concluded that the model was suitable for studying the relative contributions of altering haemodynamic patterns and venous drainage on cerebrovascular changes. We also found that hypertension modulated cerebral vascular changes in addition to disrupted blood flow

Morphological and haemodynamic characteristics of cerebral arteries in sham and AV fistula rats.

<p>ICA: internal carotid artery. MCA: middle cerebral artery. ACA: anterior cerebral artery.</p><p>*^#indicate significant different from WKY of the same group (sham or fistula).</p>†<p>indicates significant different from sham groups. <i>P<0.05.</i></p

Representative histological sections at respective arteries of sham SHR.

<p>Top panel: ICA, middle panel: MCA and bottom panel: ACA. Left pictures were taken at 10x magnification. Squares in the left panel indicate ROI magnified on the right magnified at 40x. All images follow the same scale bar of the image in their corresponding top panel.</p

Representative histological sections at respective arteries of fistula SHR.

<p>Top panel: ICA, middle panel: MCA and bottom panel: ACA. Left pictures were taken at 10x magnification. Squares in the left panel indicate ROI magnified on the right magnified at 40x. Unfilled triangle shows endothelium. Diamond filled triangle shows elastin lamellae. Brick filled triangle shows basement membrane. All images follow the same scale bar of the image in their corresponding top panel.</p

Shrinkage of cerebral vessels before and after AV fistula.

<p>Rats were sacrificed 4 weeks post operated and shrinkage was calculated from a percentage between fistula group and their respective controls. Top panel shows right arteries and bottom panel shows the left. Values are mean±SD. * indicates statistical significance. <i>P<0.05</i>.</p

Surgical training technology for cerebrovascular anastomosis

Cerebrovascular anastomosis (for example in the management of Moyamoya disease or complex aneurysms) is a rarely performed but essential procedure in neurosurgery. Because of the complexity of this technique and the infrequent clinical opportunities to maintain skills relevant to this surgery, laboratory training is important to develop a consistent and competent performance of cerebrovascular anastomosis. We reviewed the literature pertaining to the training practices surrounding cerebrovascular anastomosis in order to understand the ways in which trainees should best develop these skills. A wide variety of training methods have been described. These may be classified into five general categories, according to training materials used, being synthetic material, living animal, animal carcass, human cadaver, and computer simulation. Ideally, a novice begins training with non-biological material. After gaining sufficient dexterity, the trainee will be able to practice using biological materials followed by high fidelity models prior to actual surgery. Unfortunately, the effectiveness of each model has generally, to our knowledge, only been judged subjectively. Objective quantification methods are necessary to accelerate the acquisition of competence.5 page(s

Haemodynamic analysis of vessel remodelling in STA-MCA bypass for Moyamoya disease and its impact on bypass patency

The purpose of this study is to estimate the remodelling characteristics of STA-MCA bypass and its influence on patency via the use of computational fluid dynamic (CFD) technology. The reconstructed three-dimensional geometries from MRA were segmented to create computational domains for CFD simulations. Eleven patients, who underwent regular MRA both immediately following surgery and at the six months follow-up, were studied. The flow velocities at STA were measured via the use of quantitative MRA (QMRA) to validate simulation results. STA-MCA bypass patency was confirmed for each patient immediately following surgery. The simulation indicated that the remodelling of the arterial pedicle in nine patients was associated with a reduction in the resistance to flow through the bypass. For these cases, the modelling of a driving pressure of 10. mmHg through the bypass at 6 months post-surgery resulted in a 50% greater blood flow than those found immediately following surgery. However, two patients were found to exhibit contradictory patterns of remodelling, in which a highly curved bending at the bypass immediately post-surgery underwent progression, with increased resistance to flow through the bypass at 6 months follow-up, thereby resulting in a modelled flow rate reduction of 50% and 25%, respectively. This study revealed that STA-MCA bypass has a characteristic remodelling that usually reduces flow resistance. The initial morphology of the bypass may have had a significant effect on the outcome of vessel remodelling