Cerebral Aneurysm

Excerpt

Cerebral aneurysms represent focal dilations that develop at weak points within the arterial circulation of the brain. Size varies widely, ranging from small lesions measuring less than 0.5 mm to giant aneurysms exceeding 25 mm. Most aneurysms demonstrate a saccular, or berry-shaped, morphology characterized by a thin or absent tunica media and an absent or severely fragmented internal elastic lamina. Fusiform, or circumferential, aneurysms and mycotic, or infectious, aneurysms account for a small percentage of cases, with mycotic forms considered extremely rare. Incidence in the United States approaches 13 per 100,000 population, while Japan and Finland report the highest incidence and prevalence.

Most cerebral aneurysms remain clinically silent and are discovered incidentally on neuroimaging. Approximately 85% occur within the anterior circulation, most commonly at arterial junctions or bifurcations along the circle of Willis (see Images. Anterior Communicating Artery Aneurysm and Ruptured Saccular Anterior Communicating Artery Aneurysm). Rupture frequently results in subarachnoid hemorrhage (SAH), a condition associated with substantial morbidity and mortality.