Growth rates of intracranial aneurysms: exploring constancy

Abstract

R esearch on the development of intracranial aneurysms has been performed in numerous fields such as hemodynamics, 18 biomechanics, 4 histology, 6 and computational fluid dynamics. 21 Although these studies have provided new information regarding factors involved in aneurysm development, the results cannot be directly related to the growth rates of aneurysms. Given that an aneurysm's size is a main determinant in its risk of rupture, 26 lesion growth rates are a key factor in the relation among aneurysm prevalence, the risk of aneurysm rupture, and the observed incidence of SAH. Although aneurysm growth has been suggested to be erratic, 12 existing models of aneurysm screening or treatment generally incorporate a constant time-independent growth rate and risk of rupture. Aneurysms that grow fast in a short period of time [14][15][16]30,31 are likely to have high risks of rupture for short periods of time.11 Variable growth rates with corresponding time-variable risks of rupture will change predictions of the SAH risk over different time intervals. Evidence regarding the actual growth process may support or challenge current assumptions and perhaps evoke new screening and/or treatment strategies for unruptured aneurysms. 24,33Limited empirical data exist on the change in, or the consistency of, aneurysm growth rates over time. Extensive data collection on growth rates is not feasible, because it would require frequent screening-for example, with MR angiography-of large groups of healthy individuals and persons with unruptured aneurysms. Thus, insight into aneurysm growth rates can be attained only by modeling the effects of different growth rates on aneurysms sizes and SAH incidence and comparing these results with the observed incidence of SAH in an actual population. We constructed a model suitable for the simulation of individual patient histories. Drawing from a parametric distribution, aneurysm growth rates were assigned to individuals. As aneurysm formation and Object. The annual rate of rupture of intracranial aneurysms is often assumed to be constant, but it is unknown whether this assumption is true. Recent case reports have suggested that aneurysms grow fast in a short period of time. The authors of the present report investigated the plausibility of a constant growth rate for intracranial aneurysms.Methods. Assuming a constant aneurysm growth rate within an individual and varying rates between individuals, a hypothetical cohort was simulated. Individuals with high growth rates will display aneurysm formation and rupture at a young age; such persons disappear early from the hypothetical cohort. As a result the mean lesion growth rate varies over time. In hypothetical cohorts with different initial mean growth rates, the authors calculated age-specific incidence rates (per 100,000 person-years) of subarachnoid hemorrhage and compared these rates with populationbased data on the incidence of subarachnoid hemorrhage (per 100,000 person-years).Results. A hypothetical cohort with a mean initial growth rate o...

Pediatric Intracranial Aneurysms: New and Enlarging Aneurysms after Index Aneurysm Treatment or Observation

“…Thus, it seems likely that pediatric patients develop new and enlarging aneurysms at a faster pace than their adult counterparts. The probable inconstancy of aneurysm growth rates, 9 as underscored by patient 1 (Fig 3), makes it challenging to develop a protocol for aneurysm imaging surveillance that would be applicable to all pediatric patients.…”

Unruptured intracranial aneurysms: initial and follow-up screening

“…We assumed a constant rate of development throughout life, although an irregular and discontinuous growth rate is more likely. 54 Also, we did not incorporate additional risk factors for aneurysm development and rupture such as smoking, hypertension, and excessive use of alcohol in our analysis. It is possible that more frequent screening is more cost-effective in persons with both a positive family history and exposure to these additional risk factors.…”

“…At the start of this thesis, very short-term follow-up (1-2 years) seemed inefficient in small aneurysms, as aneurysms grew during the first years of follow-up in only about 2% of the patients. [52][53][54] A considerable number of aneurysms do grow over the course of 10-20 years of follow-up (Table 1.1). 30,[52][53][54][55][56][57][58][59][60] Risk factors for aneurysm growth differ per study and confidence intervals are usually wide.…”

“…[52][53][54] A considerable number of aneurysms do grow over the course of 10-20 years of follow-up (Table 1.1). 30,[52][53][54][55][56][57][58][59][60] Risk factors for aneurysm growth differ per study and confidence intervals are usually wide. Current smoking, 30,30,56,56 aneurysm size, 55,57 multiple aneurysms, 55,57 positive family 1 1 history 55 and positive family history in combination with history of SAH 61 were all found as possible risk factors at the start of this thesis, but none of them consistently showed up in all studies, and multivariable analyses were not always possible due to small sample sizes.…”

Modeling and simulation of flow in cerebral aneurysms

“…A low wall shear stress may facilitate the growing phase and may trigger the rupture of a cerebral aneurysm by causing degenerative changes in the aneurysm wall. The situation is, however, more complex, as illustrated by the phenomenon of spontaneous stabilization of aneurysms after an initial phase of growth [44]. It is still very much an open issue what the precise correlation is between shear stress patterns and general circulation on the one hand, and developing medical risks such as aneurysm rupture, on the other hand.…”