Object: Arachnoid cysts are a frequent finding on intracranial imaging in children. The prevalence and natural history of these cysts are not well defined. The authors studied a large consecutive series of children undergoing MR imaging to better define both the MR imaging-demonstrated prevalence and behavior of these lesions over time.
Methods: The authors reviewed a consecutive series of 11,738 patients who were 18 years of age or younger and had undergone brain MR imaging at a single institution during an 11-year period. In the patients in whom intracranial arachnoid cysts were identified, clinical and demographic information was recorded and imaging characteristics, such as cyst size and location, were evaluated. Prevalence data were analyzed using univariate and multivariate logistic regression, linear regression, and ANOVA. All patients with sufficient data (repeat MR imaging studies as well as repeated clinical evaluation over at least 5 months) for a natural history analysis were identified. This group was assessed for any change in symptoms or imaging appearance during the follow-up interval.
Results: Three hundred nine arachnoid cysts (2.6% prevalence rate) were identified. There was an increased prevalence of arachnoid cysts in males (p < 0.000001). One hundred eleven patients met all criteria for inclusion in the natural history analysis. After a mean follow-up of 3.5 years, 11 arachnoid cysts increased in size, 13 decreased, and 87 remained stable. A younger age at presentation was significantly associated with cyst enlargement (p = 0.001) and the need for surgery (p = 0.05). No patient older than 4 years of age at the time of initial diagnosis had cyst enlargement, demonstrated new symptoms, or underwent surgical treatment.
Conclusions: Arachnoid cysts are a common incidental finding on intracranial imaging in pediatric patients. An older age at the time of presentation is associated with a lack of clinical or imaging changes over time.