[Subependymoma of the septum pellucidum. MRI features and its usefulness in planning surgery].

A 61-year-old female was referred because of headache and gait disturbance. A computed tomography (CT) scan revealed a midline isodense mass lesion. The limit of the tumor was equivocal even after administration of contrast medium. Magnetic resonance imaging (MRI) study, however, clearly showed the relationship between the tumor and the surrounding structures, such as the corpus callosum, the ventricular cavities. The tumor had originated from the region of the septum pellucidum and positioned just beneath the corpus callosum from the genu to the splenium with the roof of the third ventricle pushed downward. The tumor was totally extirpated via the interhemispheric paratranscallosal route. The tumor was typical subependymoma. The post-operative course was uneventful. Transient psychiatric disturbance and inability to retain recent memory were observed and the former subsided in several weeks. CT and MRI characteristics of subependymoma are summarized and the usefulness of MRI to locate tumors and to plan proper surgical approaches are emphasized.