What are the four types of cerebral aneurysms?

• A. Saccular; fusiform; dissecting; mycotic
• B. Atherosclerotic; inflammatory; traumatic; congenital
• C. Berry; Charcot-Bouchard; saccular; fusiform
• D. Mycotic; scirrhous; mucinous; traumatic

Answer: (A)

Cerebral aneurysms are categorized by how the vessel wall dilates or is damaged. The four recognized forms are saccular (berry) aneurysms at branch points in the circle of Willis, fusiform aneurysms which involve a segment of the vessel dilating circumferentially, dissecting aneurysms where a tear in the vessel wall creates a false lumen, and mycotic aneurysms caused by infectious processes often from septic emboli. Saccular/berry aneurysms are the most common and classically rupture to cause subarachnoid hemorrhage. Fusiform aneurysms reflect diffuse vessel disease such as atherosclerosis and can lead to rupture or mass effect. Dissecting aneurysms arise from a breach in the intima with blood separating layers of the wall, presenting with acute hemorrhage or stroke-like symptoms. Mycotic aneurysms are infectious in origin and can enlarge rapidly due to inflammatory destruction of the vessel wall.

The other options mix etiologies or nonstandard labels (for example, microaneurysms of Charcot-Bouchard vessels are small penetrating-artery lesions associated with hypertensive hemorrhage rather than a major cerebral aneurysm type, and terms like scirrhous or mucinous do not define aneurysm categories).