Pathologic Findings and Clinical Course of Midline Paraventricular Gliomas Diagnosed Using a Neuroendoscope.

INTRODUCTION: Removal of midline paraventricular gliomas is difficult because of their deep localization and invasive character, requiring biopsy for pathologic diagnosis. This study aimed to assess the pathologic findings and clinical course of midline paraventricular gliomas diagnosed using a neuroendoscope.

METHODS: This study was performed as a retrospective investigation using a neuroendoscope of 26 patients whose tumors were diagnosed as midline paraventricular gliomas. The main loci of the lesions were the thalamus (11 patients), tectum (6 patients), and other areas (9 patients). Of these 26 patients, 21 (81%) had accompanying obstructive hydrocephalus. Surgery was performed via the lateral ventricle using a flexible scope. For patients with obstructive hydrocephalus, we added endoscopic third ventriculostomy, septostomy, and/or plasty of the foramen of Monro. Pathologic diagnosis was determined according to hematoxylin-eosin staining and immunohistochemistry using anti-GFAP, anti-Ki-67, anti-H3-K27M, and anti-IDH1-R132H antibodies.

RESULTS: The pathologic diagnoses were grade I (5 patients), grade II (3 patients), grade III (6 patients), and grade IV (4 patients) gliomas. Six patients were diagnosed as having high-grade glioma, which was difficult to distinguish between grade III and grade IV. Two patients were undiagnosable. H3-K27M was strongly positive in 8 of 15 patients with high-grade glioma. All patients with high-grade gliomas died or received best supportive care within 2 years after surgery.

CONCLUSIONS: Neuroendoscopic surgery is useful for midline paraventricular gliomas in terms of the treatment of obstructive hydrocephalus, as well as pathologic diagnosis and genetic analysis, which are required under the World Health Organization 2016 classification.