Unruptured Intracranial Aneurysms: Current Perspectives on the Origin and Natural Course, and Quest for Standards in the Management Strategy

Abstract

Unruptured intracranial aneurysms are relatively common, and can cause subarachnoid hemorrhage. Management of unruptured intracranial aneurysms requires knowledge of the natural course and management risks of individual aneurysms. Current knowledge on the natural course and management risks is summarized and our current management strategy presented. Extensive literature review was conducted to identify risk factors influencing the natural course and management outcome of unruptured intracranial aneurysms. Our consecutive surgical series from October 2006 through June 2009 were reviewed retrospectively. The risk factors for rupture were size and location, as well as history of subarachnoid hemorrhage in small aneurysms. Management morbidity was significantly influenced by the size, location, and patient's age. Since 2006, we have monitored motor evoked potentials in all surgeries of cerebral aneurysms and utilized endoscope control, and skull base and bypass techniques in selected cases. In 133 consecutive surgeries, two patients (1.5%) suffered severe neurological morbidity. Unruptured intracranial aneurysms have various clinical characteristics and we need to stratify management strategy according to the aneurysm features such as size, location, shape, and patient's clinical status. In Japan, with national efforts to elevate management standards, morbidity associated with the treatment of the unruptured intracranial aneurysms is relatively low. To improve future care further, we need to continue seeking better and less invasive management modalities and technique.

Cardiac Cycle-Related Volume Change in Unruptured Cerebral Aneurysms

“…Although the rupture rate of unruptured cerebral aneurysms is reported to be quite low, [1][2][3][4][5][6][7] rupture results in subarachnoid hemorrhage with potentially devastating consequences. In addition to etiologic surveys, 2,7-9,17 computational simulation of the flow at and around an aneurysm has generated extensive interest as a means to discovering the underlying hemodynamic mechanism(s) that cause physical stress to the aneurysmal wall, possibly resulting in aneurysmal rupture.…”

“…The rate of rupture of these aneurysms is reported to be 0.3% to 4.0% per year [1][2][3][4][5][6][7] and appropriate management is required. Risk assessment of future rupture leading to subarachnoid hemorrhage is important in the decision to intervene with these unruptured aneurysms.…”

Risk of Rupture of Small Anterior Communicating Artery Aneurysms Is Similar to Posterior Circulation Aneurysms

“…[9][10][11][12][13][14][15] We also included those additional factors identified by a systematic Cochrane literature review of reviews 16 as having significant RR associated with SAH in the general population, including positive family history (RR,4.0 [95% CI,), smoking (RR,2.4 [95% CI,), alcohol consumption of >150 g/wk (RR, 2.1 [95% CI, 1.5-2.8]), hypertension (RR,2 [95% CI,). …”

Magnetic resonance fluid dynamics for intracranial aneurysms—comparison with computed fluid dynamics

“…Recent neuroimaging examination can often detect incidental unruptured intracranial aneurysms, which are thought to be present in 2-6% of the total population [17,18]. Some studies reported a rupture rate of about 0.1-2% per year for unruptured aneurysms; however, the specific risk for rupture is still unknown [17].…”

“…To determine the management strategy for unruptured aneurysms, we need to estimate the natural history and management risk of individual aneurysms [17]. CFD has been studied to clarify the mechanism of rupture and development of aneurysms from the standpoint of flow dynamics and WSS.…”