What are saccular aneurysms and their different types?

From the Guidelines

Saccular aneurysms are a type of aneurysm that forms on blood vessel walls, most commonly in cerebral arteries, and can be classified into different types based on their size and morphology, including small, medium, giant, simple, complex, and fusiform aneurysms, with berry aneurysms and blister aneurysms being common subtypes 1.

Classification of Saccular Aneurysms

The classification of saccular aneurysms is based on their size and morphology.

• Small aneurysms measure less than 10mm in diameter
• Medium aneurysms range from 10-25mm
• Giant aneurysms exceed 25mm

Morphological Classification

Morphologically, saccular aneurysms can be classified as:

• Simple (regular dome with smooth contours)
• Complex (irregular shape with lobulations)
• Fusiform (spindle-shaped dilations)

Subtypes of Saccular Aneurysms

There are several subtypes of saccular aneurysms, including:

• Berry aneurysms, which are a common subtype occurring at arterial bifurcations in the Circle of Willis
• Blister aneurysms, which are small, fragile lesions with thin walls that typically form on non-branching sites of arteries
• Microaneurysms, which are very small (less than 3mm) and often associated with hypertension

Risk Factors and Development

Saccular aneurysms develop due to hemodynamic stress and underlying vessel wall weakness, with risk factors including hypertension, smoking, genetic conditions like polycystic kidney disease, and family history, as reported in the guidelines for the management of aneurysmal subarachnoid hemorrhage 1.

Clinical Significance

These aneurysms require careful monitoring as they can rupture, causing potentially fatal subarachnoid hemorrhage, with a 30-day mortality rate of 45% and approximately half the survivors sustaining irreversible brain damage, as stated in the recommendations for the management of patients with unruptured intracranial aneurysms 1.

From the Research

Definition of Saccular Aneurysms

• Saccular aneurysms, also known as berry aneurysms, are a type of congenital aneurysm that can cause subarachnoidal hemorrhage (SAH) when ruptured 2.
• They are typically localized in the anterior part of the circle of Willis, with most fatal cases occurring in the bifurcations.

Types of Saccular Aneurysms

• Based on size, saccular aneurysms can be classified into:
  • Small: less than 5 mm in diameter (found in 46 cases in the study) 2.
  • Medium: 5 to 10 mm in diameter (found in 10 cases in the study) 2.
  • Large: larger than 10 mm in diameter (found in 7 cases in the study) 2.
• Based on shape, saccular aneurysms can be:
  • Unilocular: single-chambered aneurysms.
  • Multilocular: aneurysms with multiple chambers (found in 9 cases in the study) 2.
• Saccular aneurysms can also be associated with other conditions, such as:
  • Atherosclerotic lesions of the arteries of the circle of Willis (found in 34 cases in the study) 2.
  • Polycystic kidney disease (found in 9 cases in the study) 2.