Describe berry aneurysms.
Most common type of cerebral aneurysms
Have a round, saccular shape
Typically occur at the junctions of vessels in the circle of Willis (the most commonly involved junction is the between anterior communicating artery and anterior cerebral artery)
Account for approx. 80% of cases of nontraumatic subarachnoid hemorrhage
Risk factors 
History of congenital conditions: autosomal-dominant polycystic kidney disease, Ehlers-Danlos syndrome, Marfan syndrome, aortic coarctation
Excessive alcohol consumption
Family history of aneurysms
Describe the fusiform aneurysm.
Dilation of the entire circumference of the artery
Most frequently occur in the vertebrobasilar system
Associated with connective tissue diseases and atherosclerosis
Describe the mycotic aneurysm.
Mushroom-shaped dilations of infected vessel walls
Caused by septic emboli (mostly due to bacterial endocarditis)
Occur at small, peripheral segments of cerebral vessels and often involve the middle cerebral artery.
Describe the traumatic aneurysm.
Comprise < 1% of all intracranial aneurysms
Most commonly occur in the supraclinoid ICA and the anterior cerebral artery
Have a high risk of rupture
Describe the charcot-boucard microaneurysm.
Associated with hypertension and diabetes.
Affect small lenticulostriate vessels in the basal ganglia and thalamus.
Their rupture is the most common cause of intracerebral hemorrhage.
List clinical features.
The mass effect of the saccular aneurysms depends on the affected vessel.
Anterior communicating artery: bitemporal hemianopia; visual acuity defects (CN II compression at the optic chiasm)
Posterior communicating artery: mydriasis (CN III parasympathetic fibers compression); ptosis and ophthalmoplegia in severe compression
See clinical features of ruptured cerebral aneurysms in the “Clinical features” section in the article on “Subarachnoid hemorrhage.”
Describe the diagnosis.
Angiography: determines location, size, and morphology of aneurysm (with the exception of Charcot-Bouchard aneurysms, which cannot be detected on angiography)
See “Subarachnoid hemorrhage” for workup of suspected aneurysmal subarachnoid hemorrhage.
Describe the treatment.
Unruptured intracranial aneurysms
Conservative management includes maintaining normal blood pressure, cessation of smoking, and imaging follow-up.
Surgical clipping or endovascular coiling can be considered for patients with life expectancy of > 10 years in the following cases:
Large (> 5 mm) or increasing during follow-up aneurysm
Location in the posterior circulation or communicating arteries
History of subarachnoid hemorrhage
Ruptured aneurysms: See “Subarachnoid hemorrhage.”