Hormones, radiosurgery and virtual reality: new aspects of meningioma management.

The understanding and management of meningiomas is changing significantly today. One of the most striking features of their pathophysiology is their predominance in women. In a series of 517 patients with meningiomas seen by the Brain Tumor Group at Brigham and Women's Hospital, the female:male ratio was 24:1. The progesterone receptor appears to be the major candidate to explain this difference. Although meningioma cells variably express receptors for estrogen, androgen, platelet-derived growth factor, epidermal growth factor, and somatostatin, these molecules do not explain the differences because they are not differentially expressed or are not activated. Progesterone receptor can be shown to be expressed in 81% of women and 40% of men with meningiomas; it can also be shown to be activated by transfecting a construct with the progesterone responsive element and a reporter in it and using the cell's own receptors to activate this construct. Surgery remains the mainstay of meningioma management. At the Brigham and Women's Hospital three-dimensional reconstruction techniques have markedly improved the ability to visualize the tumor as well as its relation to vascular structures. With MRI reconstruction, it is possible to know the tumor's relation to the sagittal and other sinuses, to identify feeders and proximity to major arteries, and to establish its location and relation to cortex by frameless stereotaxis. These techniques can be used in a virtual reality format are some of the most powerful in neurosurgery both for teaching and for the surgical procedure itself. External beam radiation has been shown by others to be an effective adjunctive treatment to prevent meningioma recurrence. Recently, linear accelerator radiosurgery and stereotactic radiotherapy have changed the pattern of radiation at our institution. In a series of 56 skull base meningiomas, for example, 95% were controlled (i.e., showed no growth) over a four year period. Fractionated focal radiation potentially offers the same control rate with fewer complications. With increasing understanding and treatment possibilities, meningiomas remain one of the most intriguing and challenging tumors in the nervous system.