Meningeal hemangiopericytomas make up approximately 0.4% of all primary CNS tumors. These types of tumors tend to appear at a younger age than meningiomas, and they occur more often in men than in women (Jääskeläinen et al. 1985).
In the series described in the literature, MR imaging findings and site manifestations were similar to those of meningiomas, but with slight differences (Ruscalleda et al. 1994; Akiyama et al. 2004).
Hemangiopericytomas had a more multilobular appearance with sometimes-irregular margins and strong enhancement, including the adjacent meningeal structures. Unlike meningiomas, they did not show hyperostosis or calcification. Their signal intensity has been described as various; in most cases the tumor was isointense to cortical gray matter on both T2 and unenhanced T1-weighted imaging.
A common finding in hemangiopericytoma is a homogeneous enhancing, well-demarcated tumor with low signal on T2-weighted and FLAIR imaging. On unenhanced T1-weighted imaging, the tumor was isointense to slightly hypointense compared with the gray matter.
The low signal is not related to calcification but probably to a high vascular density within the lesion. In patients with hemangiopericytomas, imaging of the complete neuroaxis is mandatory to rule out metastases.
- M.F. Reiser, W. Semmler, H. Hricak (Eds.) "Magnetic Resonance Tomography", Springer 2008