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 2.4:1.
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.
J. Neurol. Sci. 1997; 24: 302-306