Snapshot A 58-year-old woman presents to the emergency department with a severe headache of sudden onset. The headache occurred immediately while at rest, and she describes the headache as the most severe she has ever had. Her headache symptoms are also accompanied by photophobia. She has tried ibuprofen and sumatriptan, but it has not improved her symptoms. Medical history is significant for migraine headache, hypertension, cigarette smoking, and alcohol use disorder. Physical examination is notable for nuchal rigidity. A non-contrast head CT is shown. (Subarachnoid hemorrhage) Saccular Aneurysm Clinical definition a balloon-like outpouching of the vessel wall which is also referred to as berry aneurysms which are composed of a neck that is connected to the originating vessel and and dome that has the possibility to rupture Saccular (berry) aneurysm these aneurysms typically arise from branch points (bifurcations) of the circle of Willis are more prone to rupture than fusiform aneurysms aneurysm locations anterior communicating artery (most common) clinical correlate bitemporal hemianopsia secondary to aneurysm compression of the optic chiasm posterior communicating artery clinical correlate ipsilateral oculomotor nerve palsy secondary to aneurysm compression middle cerebral artery risk factors hypertension increasing age smoking autosomal dominant polycystic kidney disease (ADPKD) Ehlers-Danlos syndrome Moyamoya syndrome Charcot-Bouchard Aneurysm Clinical definition small vessel aneurysm (e.g., lenticulostriate arteries) that result from chronic hypertension can rupture, leading to an intraparenchymal hypertensive hemorrhage which commonly affects the basal ganglia thalamus cerebellum pons