Do arachnoid cysts grow? A retrospective volumetric study

Area of Science:

• Neurology
• Radiology
• Neurosurgery

Background:

• Arachnoid cysts (ACs) are common incidental findings on cranial MRI.
• ACs are often presumed to cause symptoms due to growth and pressure on brain tissue.

Purpose of the Study:

• To investigate the growth patterns of arachnoid cysts over time.
• To determine if ACs increase in size and which types are prone to growth.

Main Methods:

• Retrospective analysis of a large database of cranial MRI scans.
• Inclusion of 166 arachnoid cysts from 50 individuals with a mean observation period of 2.5 years.

Main Results:

• The majority of arachnoid cysts remained stable in size or decreased.
• Only larger Galassi II arachnoid cysts at the temporal pole demonstrated statistically significant growth (0.3 ml/year).
• All studied cysts were clinically silent, with no associated symptoms.

Conclusions:

• Most arachnoid cysts do not grow and maintain their size or shrink.
• The assumption that AC growth causes symptoms may not apply to the majority of cases.
• This study provides Class III evidence supporting the stability of most ACs.