Role of hemodynamics forces in unruptured intracranial aneurysms: An overview of a complex scenario

Background: The understanding of unruptured intracranial aneurysms (IAs) natural history has always played a critical role in pre-surgical or endovascular planning, in order to avoid possible fatal events. Size, shape, morphology and location are known risk factors for aneurysm’s rupture, but morphologic parameters alone, may not be sufficient in order to perform a proper rupture risk stratification. Methods: We performed a systematic PUBMED search and focused on hemodynamics forces which may influence aneurysmal initiation, growth and rupture. Results: We included 223 studies describing several hemodynamic parameters related to aneurysm natural history. In these studies, different modalities of aneurysm models creation have been used in order to perform flow evaluation and to provide a comprehensive analysis of IAs evolution. To date, a great deal of controversies exist about the correlation between these parameters and initiation, growth, rupture risk or stabilization of the aneurysmal sac. Recent findings have also showed the importance of flow patterns in this process and the relationship between unruptured IAs geometry and hemodynamic parameters. Conclusions: Hemodynamic forces’ role in unruptured IAs natural history evaluation present an inherited complexity and are still not completely understood. In this complex scenario, although several attempts were described in literature, a proper risk rupture stratification and treatment strategy selection based on hemodynamic forces has not been yet created. Further efforts should be done in order to accomplish this important goal.