Meningeal Tumours: a Review.

The tumours to be considered here are those arising primarily in the meninges, or gaining access to them as secondary growths. It will be necessary to consider not only the dura and leptomeninges that invest the brain and spinal cord, but also their extensions into the brain as the tela choroidea and stroma of the choroid plexuses, and the sheaths of the perforating blood-vessels that form the outer boundary of the Virchow-Robin spaces. In the vertebral canal the separation of the dura from the bone by the epidural adipose and areolar tissue, and the resolution of the arachnoid and pia into two distinct membranes, introduce additional factors that are of importance, especially in the direct spread of tumours and the dissemination of their cells by the cerebrospinal fluid. Although little has been heard of it lately, the old controversy as to whether the meninges are of mesodermal or of ectodermal origin cannot be regarded as satisfactorily resolved. In practice, however, it is undisputed that the primary meningeal tumours (meningiomas) display many features in common with mesodermal tumours in other parts of the body; the question of embryological origin is thus purely academic.