Incidence rates of cranial aneurysms are estimated at between 0.4% and 3.6%. Those without risk factors have expected prevalence of 2–3%. In adults, females are more likely to have aneurysms. They are most prevalent in people ages 35 – 60 but can occur in children as well. Aneurysms are rare in children with a reported prevalence of .5% to 4.6%. The most common incidence is among 50-year-olds, and there are typically no warning signs. Most aneurysms develop after the age of 40. Pediatric aneurysms Pediatric aneurysms have different incidences and features than adult aneurysms. Intracranial aneurysms are rare in childhood, with over 95% of all aneurysms occurring in adults. Risk factors Incidence rates are two to three times higher in males, while there are more large and giant aneurysms and fewer multiple aneurysms. Intracranial hemorrhages are 1.6 times more likely to be due to aneurysms than cerebral arteriovenous malformations in whites, but four times less in certain Asian populations. Most patients, particularly infants, present with subarachnoid hemorrhage and corresponding headaches or neurological deficits. The mortality rate for pediatric aneurysms is lower than in adults. Modeling Vortex formation inside an aneurysm. 1- Blood flow inlet. 2- Vortex formation inside aneurysm. Velocity at center is near zero. 3- Blood flow exit Modeling of aneurysms consists of creating a 3D model that mimics a particular aneurysm. Using patient data for the blood velocity, and blood pressure, along with the geometry of the aneurysm, researchers can apply computational fluid dynamics (CFD) to predict whether an aneurysm is benign or if it is at risk of complication. One risk is rupture. Analyzing the velocity and pressure profiles of the blood flow leads to obtaining the resulting wall shear stress on the vessel and aneurysm wall. The neck of the aneurysm is the most at risk due to the combination of a small wall thickness and high wall shear stress. When the wall shear stress reaches its limit, the aneurysm ruptures, leading to intracranial hemorrhage. Conversely, another risk of aneurysms is the creation of clots. Aneurysms create a pocket which diverts blood flow. This diverted blood flow creates a vortex inside of the aneurysm. This vortex can lead to areas inside of the aneurysm where the blood flow is stagnant, which promotes formations of clots. Blood clots can dislodge from the aneurysm, which can then lead to an embolism when the clot gets stuck and disrupts blood flow. Model analysis allows these risky aneurysms to be identified and treated. In the past, aneurysms were modeled as rigid spheres with linear inlets and outlets. As technology advances, the ability to detect and analyze aneurysms becomes easier. Researchers are able to CT scan a patient's body to create a 3D computer model that possesses the correct geometry. Aneurysms can now be modeled with their distinctive "balloon" shape. Nowadays researchers are optimizing the parameters required to accurately model a patient's aneurysm that will lead to a successful intervention. Current modeling is not able to take into account all variables though. For example, blood is considered to be a non-Newtonian fluid. Some researchers treat blood as a Newtonian fluid instead, as it sometimes has negligible effects to the analysis in large vessels. When analyzing small vessels though, such as those present in intracranial aneurysms. Similarly, sometimes it is difficult to model the varying wall thickness in small vessels, so researchers treat wall thickness as constant. Researchers make these assumptions to reduce computational time. Nonetheless, making erroneous assumptions could lead to a misdiagnosis that could put a patient's life at risk.
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