Benign cystic lesions in the central nervous system. Light and electron microscopic observations of cyst walls

A wide variety of benign cystic lesions is known to occur in both adults and children. Recent advances in diagnostic radiology have facilitated meaningful surgical intervention in most instances. It is convenient to classify these cysts into two groups. The first group includes those that arise from defects wholly within the central nervous system. Among these are certain static lesions such as cystic cavities arising from infarcts and other destructive lesions. Some of these are observed to communicate with the subarachnoid space or ventricle. The progressive lesions in this group include arachnoid cysts, ependymal cysts, cystic hemangioblastoma, cystic cerebellar astrocytoma, and certain infectious processes. The second group is constituted by cysts resulting from the intrusion of non-nervous tissue into the neuroaxis, usually in the midline. These are expanding congenital lesions, although some become symptomatic only in the adult. Among these are teratomas, dermoid cysts, epidermoid cysts, craniopharyngiomas, Rathke's cleft cysts, and other epithelial cysts apparently derived from the upper respiratory or the intestinal tract. Colloid cysts of the III ventricle are usually considered to be neuroectodermal in origin, but certain features suggest an endodermal origin.