[Meningioma of the lateral ventricle. 3 recent cases].

Three recent cases of intra-ventricular meningiomas are reported. The incidence of this tumor type is very low, since they account for only 0.2% of all intra-cranial neoplasms and 2% of all intra-cranial meningiomas in the adult. In our first 2 cases, the meningioma involved the right trigonal area. In our third patient, a 14 year-old girl, the tumor had involved the left occipital horn. It is usually assumed that their development is a result of meningothelial inclusion bodies normally present in the arachnoid of the tela choroidea. As mentioned in previous reports, their clinical presentation may be that of paroxysmal increased intra-cranial pressure and a mechanism of trapped ventricular horn has been advocated. However, under such circumstances, an intraventricular bleeding seems to be a more likely mechanism. Despite their rarety, intra-ventricular meningiomas are usually diagnosed on C.T. It typically shows a hyperdense mass, attached to the plexus and enhancing after contrast infusion. In one of our patients (obs. 2), the meningioma manifested on M.N.R. by a low signal intensity in T1 sequences and by a high signal in T2 sequences. In our third patient, the M.N.R. findings were indicative of a cystic lesion lying in the occipital horn, but not of a meningioma, the diagnosis of which was made on further microscopic examination. The angiographic evaluation remains useful to document preoperatively the arterial supply to the meningioma, which is mainly from the postero-lateral choroïdal arteries. At operation, anterior meningiomas lying near the foramen of Monro are easily exposed through a transfrontal approach and raise no technical problem.(ABSTRACT TRUNCATED AT 250 WORDS)