Expansion of arachnoid cysts in children: report of two cases and review of the literature.

Arachnoid cysts are intracranial, space-occupying lesions that typically remain stable in size on serial imaging. The authors describe two cases of rapidly enlarging arachnoid cysts, including one located in the anterior fossa. In the first case a 7-month-old boy presented with increasing head circumference and a rapidly enlarging arachnoid cyst in the left middle fossa, which had been documented by serial imaging over the preceding 6 months. In the second case a 4-year-old girl presented with an arachnoid cyst compressing the right frontal lobe. The cyst had not been present on imaging studies performed during the perinatal period. In both cases, a craniotomy for open fenestration of the cyst was performed with successful resolution of the mass effect. Rare cases of expansion of arachnoid cysts have been reported in the literature. In this article the authors report the dramatic enlargement of two arachnoid cysts, including the first description of enlargement of an arachnoid cyst located in the anterior fossa.