Arachnoid cysts in children: ultrastructural findings.

Light and electron microscopic features of four arachnoid cysts in children are presented. The wall of the cyst appeared composed of a dense collagen tissue in which dark and clear cells were intermingled without any specific arrangement. Abutting onto this membrane, at the luminal surface, these cells were arranged in layers. Tight junctions between arachnoid cells were absent. It is suggested that the arachnoid cysts derive from a developmental aberration of the meninges.