NEURORADIOLOGICAL ASPECTS OF INTRACRANIAL EPIDERMOIDS

Intracranial epidermoids are primarily extracerebral congenital cysts. Intra- and extradural types are differentiated: intradural lesions or iginate in the intracranial CSF spaces, and extradural lesions in the bony skull. Epidermoids increase in size passively as the result of an increase in the cyst volume and not because of active growth. Clinica lly epidermoids behave like benign, slow-growing cerebral tumours. Dif ferential diagnosis includes other cysts and cystic tumours. Neuroradi ologically epidermoids present as polycystic lesions showing extensive growth in the extracerebral CSF spaces and secondary invagination of the brain. On CT and MR, despite the high cholesterol content, epiderm oids show the characteristics of liquor and not those of fat. It can b e shown that the typical CT and MR appearance of an epidermoid is due to the different proportions of CSF in the cyst content, which results from diffusion or dehiscence of the cyst capsule. The present study w as based on analysis of 6 cases selected from a total of 29 patients w ith CNS epidermoids.