Subependymal seeding of low-grade oligodendroglial neoplasms: a case series.

The CSF dissemination of low-grade glial tumors is a known albeit rare entity. Few cases have been reported in the literature. We describe a unique series of six patients with supratentorial low-grade gliomas who presented to our institution at ages 20-41 years, and developed signal abnormality along the margin of the fourth ventricle without enhancement at variable times during their disease course (0 to 95 months). MR spectroscopy and perfusion-weighted imaging through the region of abnormality in two of these patients were consistent with a low-grade glial tumor. We hypothesize that this finding represents dissemination of the supratentorial low-grade glioma along the ventricular ependyma or through the ventricular CSF. Although the small size of our series does not allow us to draw statistically significant conclusions, this abnormality correlates with progression of the supratentorial disease with or without features of a higher grade malignancy. Additional variables that were present in all six patients include the presence of an oligodendroglial component within the supratentorial tumor, mutated IDH1, and the supratentorial tumor contacting the ventricular margin. All six patients were males.