EROSION of the cranial bones from pressure of a leptomeningeal cyst is an uncommon, but not rare, condition. While the majority of such cysts develop after severe trauma to the skull, usually with fracture, there is evidence that congenital abnormalities in the dura and leptomeninges may contribute to their production. Haymaker and Foster1 reported a case in which a large collection of clear, colorless fluid resembling cerebrospinal fluid was found enclosed between the two layers of the dura in the posterior cranial fossa; a small defect was present beneath the tentorium, through which a lobule of the cerebellum was herniated. While their patient gave a history of a fracture of the skull in childhood, the separation of the dural layers and the small subtentorial defect may have been congenital abnormalities which favored development of a cyst in this location.
Leptomeningeal cysts have been noted more commonly in the parietal,
SOULE AB, WHITCOMB BB. EXTENSIVE EROSION OF THE BASE OF THE SKULL FROM A LEPTOMENINGEAL CYSTReport of a Case. Arch NeurPsych. 1946;55(4):382-387. doi:10.1001/archneurpsyc.1946.02300150086006