Intraparenchymal schwannomas: report of two new cases studied with MRI and review of the literature.

Intraparenchymal schwannomas are very rare tumours. We present two young adult patients operated for this type of lesion who show no signs of recurrence 2 years after surgery. These tumours have a bimodal peak of presentation: most occur in young patients under 25 years, and the rest present in the elderly. Characteristically they show both Antoni A and Antoni B areas, intense inmunoreactivity to S-100 and Vimentin protein, and none to EMA or CD34. Electron microscopy is diagnostic when basal membrane is found around the cytoplasmatic processes. MRI spectroscopy depicts increased myoinositol, choline and lipids, and perfusion MR demonstrates high rCBV with a characteristic curve due to the total absence of blood brain barrier. An origin in the Schwann cells of the perivascular nervous plexus in the subarachnoid space is the most accepted theory for the histogenesis of these tumours. We propose to perform the characterization of a series of markers such as SOX-10 in every new case in order to prove that theory.