A saccular aneurysm is a type of aneurysm that forms an outward, sac-like (saccule) bulge on only one side of an artery wall. The term “saccular” comes from the Latin “sacculus” (small sac) and describes how the aneurysm balloons asymmetrically, like a localized bubble, involving only a discrete point of the vessel rather than its entire circumference. It typically consists of a rounded or oval dome connected to the vessel by a narrow neck. Its most classic example is the “berry aneurysm” seen at the branching points of the brain’s blood vessels.
Difference From a Fusiform Aneurysm
Aneurysms are fundamentally classified into two types by shape. A saccular aneurysm is a localized, sac-shaped bulge on one side of the wall, whereas a fusiform aneurysm is a symmetrical, spindle-shaped dilation involving the entire circumference of the vessel. This distinction is not merely an imaging description; the narrow neck of the saccular form provides an important technical advantage in endovascular treatment (for example, coil embolization or clipping), while such approaches are more difficult with the fusiform form.
Where It Occurs and Why It Matters
Saccular aneurysms most commonly arise in the brain (cerebral/intracranial) circulation, particularly at the arterial branching points around the circle of Willis, where hemodynamic stress and structural weakness in the wall combine. They are clinically very important because their rupture leads to subarachnoid hemorrhage. However, saccular morphology can also occur in the aorta and other arteries. Features such as an irregular shape, a lobulated structure, or a “bleb” (daughter sac) on the dome are regarded as signs that increase the rupture risk in this type of aneurysm.
Clinical Approach
Management of saccular aneurysms is determined by their size, shape, location, and rupture status. Small unruptured aneurysms are generally monitored with serial imaging, while endovascular (coiling, flow-diverting stent) or surgical (clipping) treatment is considered for aneurysms that exceed a certain size threshold, have an irregular appearance, or are in high-risk locations. The classic narrow-necked saccular form is, in most cases, suitable for endovascular techniques.
This content is for general informational purposes and is not a substitute for medical advice. For a known or suspected aneurysm, diagnostic and treatment decisions should be made in consultation with a physician.