Evaluation of routine skull films in intracranial meningiomas.

Abstract

The meningioma is a slow growing, benign tumor of the arachnoid, which occurs with relative frequency in the intracranial cavity. It represents about 12 to 15 per cent of all intracranial tumors (22, 24, 26). It is quite variable in size, and is usually single, though it may be multiple. It occurs for the most part in adults, but occasionally is found in children (16). It may be located extracranially, in such anatomical areas as the orbit and the spinal canal. Although benign, meningiomas may be malignant in their behavior, compressing and destroying adjacent tissues. The tumor is well encapsulated at its free margins, but at its meningeal attachment may invade the adjacent bone. Often it can be removed in its entirety; occasionally it recurs after incomplete removal. A few of these tumors develop without meningeal attachment, such as those found in the ventricles and those arising deep in the sylvian fissure. Pendergrass and Hope (21) reported one such example, having its origin in the outer table of the frontal bone, with no apparent intracranial source. The meningioma is quite variable in its location in the cranial vault; a classification as to origin was proposed by Cushing (3, 4), and was employed by Sosman and Putnam (26) in their discussion. The sites listed are: the cranial nerve foramina; the suprasellar area; the olfactory groove of the ethmoid; the sphenoid ridges; the sylvian cleft area; over the convexities of the brain; the parasaggital area; the falx; the transverse and sigmoid sinuses. Grossly, the tumor is of one of two forms. The first of these is the globular or spheroidal (rounded, ovoid, or lobulated), usually with a relatively small dural attachment. The second is the en plaque or flat type, which spreads along the dura; it is attached over a relatively broad area. The microscopic picture of the meningioma is variable; nine different types with variants were described by Cushing and Eisenhardt (4). The tumor was first thought to originate in the dura, but in the early days of neurosurgery the concept that it arose from the villi of the pia arachnoid was advanced, and this is the accepted theory today. The villi extend into the dura, so that grossly the tumor seems to arise from the latter. The term meningioma is of fairly recent origin, having been given to this tumor by Cushing. In an article written by him in 1922 (3), the following statement appears: “… and as the term employed, namely dural endothelioma, gives the wrong impression of the membrane from which the growth has originated, the designation meningiothelioma or meningioma is suggested as a compromise. This at least avoids the objection which the embryologist might raise, for strictly speaking the growths would seem to be properly called mesotheliomas of arachnoid origin.”