Intracranial aneurysm - description of size and neck + calculator

Apart from giving the dimensions of an intracranial aneurysm, its size should be cathegorized according to this table.

Description Size
Small ≤5mm
Medium <15mm
Large <25mm
Giant ≥25mm

The diameter of the neck of the aneurysm is cathegorized as well.

Description Size
Small neck ≤4mm
Wide neck >4mm

In general, there are three basic types of aneurysm shapes, but reportedly, such cathegorisation has little value.

Description Size
Saccular aneurysm saccular round outpouching from the artery
Berry aneurysm a type of saccular aneurysm with a neck (and therefore resembling a berry)
Fusiform aneurysm aneurysm without a stem, widening of a segment of an artery

The volume of an aneurysm, whether spheroid, ellipsoid, or cylindrical, can be estimated by the following formula (extrapolation to ellipsoid):
Volume=1/6 x Pi x length x width x height

Parameter Value  
Height* mm
Width* mm
Length (if only 2D imaging then use the same value as Width)* mm

* Required




1. Meyers PM, Schumacher HC, Higashida RT, Derdeyn CP, Nesbit GM, Sacks D, et al. Reporting Standards for Endovascular Repair of Saccular Intracranial Cerebral Aneurysms. Stroke. 2009 May 1;40(5):e366–e379.
2. Hacein-Bey L, Provenzale JM. Current Imaging Assessment and Treatment of Intracranial Aneurysms. American Journal of Roentgenology. 2011 Jan;196(1):32–44