general knowledge incidence: 0.2-7.9% in autopsy: 6-8/105/year for ruptured aneurysms. It is the third common CVDs and the incidence is increasing 1869 Most common in 40-60 years old Morphology: abnormal dilation of intracraniaarteries- 源自1869年的医疗仁道实践 saccular, fusiform and dissecting Often diagnosed when ruptured and cause subarachnoid hemorrhage(SAH) Mortality decreased with the improvement of diagnose and managementgeneral knowledge • incidence: 0.2-7.9% in autopsy; 6-8/105 /year for ruptured aneurysms. It is the third common CVDs and the incidence is increasing. • Most common in 40-60 years old • Morphology: abnormal dilation of intracraniaarteries- ---saccular, fusiform and dissecting • Often diagnosed when ruptured and cause subarachnoid hemorrhage(SAH). • Mortality decreased with the improvement of diagnose and management