Intracranial Aneurysms

Fig.1: Unenhanced axial CT of the head of a patient without recent trauma shows diffuse, bilateral subarachnoid hemorrhage (arrowheads), left greater than right. There is blood in the cerebral sulci as well as in the CSF cisterns.
Fig.2: Axial CT with IV contrast (angiographic technique) shows a left supraclinoid internal carotid artery aneurysm (arrow), measuring 6-7 mm.

Intracranial Aneurysms

• Dilatation or ballooning of intracranial blood vessel, small <12>25mm
• Three types: fusiform, saccular and dissecting
• Berry aneurysm is of a saccular type
• Common at branch points of large arteries that form the circle of Willis
• Anterior circulation (85% - 95%) > posterior circulation

Symptoms

• Most aneurysms are small and asymptomatic. Large ones may cause mass effect to cranial nerves and brain.
  
• Rupture usually results in subarachnoid hemorrhage (SAH) with high mortality of up to 50%
  
• Overall rupture risk is 1.9% per year, higher in women, cigarette smokers, cocaine users, symptomatic aneurysms, >10mm, and located in posterior circulation

Reference:
Ontario Health Technology Advisory Committee. Coil Embolization for Intracranial Aneurysms. January 2006.