Lékařské publikace

Understanding the risk factors leading to intracranial aneurysm (IA) rupture have still not been fully clarified. They are vital for proper medical guidance of patients harboring unruptured IAs. Clarifying the hemodynamics associated with the point of rupture could help could provide useful information about some of the risk factors. Thus far, few studies have studied this issue with often diverging conclusions.

Incidental detection of unruptured intracranial aneurysms (UIA) has increased in the recent years. There is a need in the clinical community to identify those that are prone to rupture and would require preventive treatment. Hemodynamics in cerebral blood vessels plays a key role in the lifetime cycle of intracranial aneurysms (IA). Understanding their initiation, growth, and rupture or stabilization may
identify those hemodynamic features that lead to aneurysm instability and rupture. Modeling hemodynamics using computational fluid dynamics (CFD) could aid in understanding the processes in the development of IA. The neurosurgical approach during operation of IA allows direct visualization of the aneurysm sac and its sam-pling in many cases. Detailed analysis of the quality of the aneurysm wall under the microscope, together with histological assessment of the aneurysm wall and CFD modeling, can help in building complex knowledge on the relationship between the biology of the wall and hemodynamics. Detailed CFD analysis of the rupture point can further strengthen the association between hemodynamics and rupture. In this chapter we summarize current knowledge on CFD and intracranial aneurysms.

Anterior choroidal artery aneurysms (AChoAA) represent 2–5% of intracranial aneurysms. As with other aneurysms of the supraclinoid segment of internal carotid artery (ICA) they are considered rather easily accessible surgical goals. Nevertheless, the tight anatomical relations between ICA, its main branches and perforating branches make it a surgically demanding area. The problematic feature might be the position and number of the arteries themselves. Also, the relationship between the artery and the aneurysm is critical, as the vessel might be distorted or completely hidden by the sac.

V posledních letech se rozvinula metodika počítačového modelování toku tekutin v cerebrovaskulární problematice, především pak v oblasti intrakraniálních aneuryzmat. Cílem většiny studií je pochopit patofyziologii vzniku, růstu a ruptury mozkových výdutí a určit ty rizikové hemodynamické parametry, které k těmto procesům vedou. V naší práci shrnujeme současný stav počítačového modelování toku tekutin především z pohledu chirurgie mozkových aneuryzmat a zaměřujeme se na možný přínos pro klinickou praxi.

Hemodynamic parameters play a significant role in the development of cerebral aneurysms. Parameters such as wall shear stress (WSS) or velocity could change in time and may contribute to aneurysm growth and rupture. However, the hemodynamic changes at the rupture location remain unclear because it is difficult to obtain data prior to rupture. We analyzed a case of a ruptured middle cerebral artery (MCA) aneurysm for which we acquired imaging data at three time points, including at rupture. A patient with an observed MCA aneurysm was admitted to the emergency department with clinical symptoms of a subarachnoid hemorrhage. During three-dimensional (3D) digital subtraction angiogra-phy (DSA), the aneurysm ruptured again. Imaging data from two visits before rupture and this 3D DSA images at the moment of rupture were acquired, and computational fluid dynamic (CFD) simulations were performed. Results were used to describe the time-dependent changes of the hemodynamic variables associated with rupture.

Brain aneurysm is a focal disease of cerebral wall, characterized by focal weakness and dilation of the wall. The danger of brain aneurysms is in its rupture, which carries a risk of death of around 50% and a risk of permanent deficit over 60% in those who survive. The aneurysm can be either secured or followed. The prediction of aneurysm rupture is of key value for the decision-making process and also during discussion with the patient about possibilities of treating the aneurysm. Today, the information can be mostly based on large population studies, such as the International Study on Unruptured Intracranial Aneurysm – ISUIA. However, the information is inadequate and we need to base the information more on individual characteristics of the patient the prediction based on individual characteristics of the aneurysm.

Pterionální kraniotomie představuje v neurochirurgické operativě jeden ze základních operačních přístupů. Využívá se mimo jiné v chirurgii aneuryzmat předního povodí. Alternativou
k tomuto přístupu je laterální supraorbitální kraniotomie dle prof. Hernesniemiho. V porovnání s pterionální kraniotomií je rychlejší, méně invazivní vůči temporálnímu svalu, přičemž
neomezuje přístup k intrakraniálním patologiím. Představujeme naše zkušenosti s laterální
supraorbitální kraniotomií v chirurgii pacientů s aneuryzmatem předního povodí.

Computational fluid dynamics (CFD) has grown as a tool to help understand the initiation, growth, and rupture of cerebral aneurysms. Studies continue to be conducted to correlate hemodynamic properties to what causes cerebral aneurysm initiation and rupture, but few deal specifically with aneurysm growth and most of these studies only use one time instance within the aneurysm growth history. This current study looks at four aneurysms with different sizes and locations, once at the initial detection of aneurysm and then once more at follow-up after several years of growth, in order to analyze hemodynamic and morphological changes. Results showed that although each aneurysm has its own growth story, major geometry bulk growth occurred in areas of low WSS, higher pressure, and in areas adjacent to flow deflected after impinging the wall. Wall shape remodeling near neck impingement regions occurred in areas of high total pressure, WSS, and OSI and high gradients of these variables. Geometries varied in volume growth per year from 61% to 170% with an average decrease in wall shear stress (WSS) of 9% and increase in kinetic energy (KE) of 114%. Aneurysm growth results were similar to published results with growth occurring in low WSS areas and neck impingement remodeling occurring near high WSS and high WSS gradients areas.

Computational fluid dynamics (CFD) has been studied as a tool for the stratification of aneurysm rupture risk. We performed CFD analysis in a patient operated on for a ruptured anterior communicating artery aneurysm. The point of rupture was identified during surgery. The aneurysm and blood vessels were segmented from computed tomography angiography to prepare a model for simulations. We found that the streamlines showed a concentrated inflow jet directed straight at the rupture point, and high wall shear stress was found at the point of rupture in the aneurysm sac. Thus specific local hemodynamics may be indicative of the aneurysm rupture site.

This study presents a rare case of subarachnoid hemorrhage (SAH) caused by an aneurysm formation on the posterior communicating artery (P Com), adjacent to the junction with the P1 branch in a patient with a long-lasting, bilateral occlusion of the internal carotid arteries (ICA). Furthermore, we discuss the incidence of aneurysm formation in idiopathic occlusion of the ICA.