Unruptured intracranial aneurysms: current perspectives on the origin and natural course, and quest for standards in the management strategy.

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.