Introduction
Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare condition where tumors grow in the subarachnoid space without an obvious connection to the brain or spinal cord parenchyma. PDLG is associated with rapid disease progression and mortality. The majority of these neoplasms are astrocytic, often high grade, and the diagnosis is usually made postmortem [1, 2]. Dissemination of oligodendrogliomas in the subarachnoid space (leptomeningeal oligodendrogliomatosis) is usually secondary to invasion of the leptomeninges or ventricular system by a primary intraparenchymal oligodendroglioma [3, 4]. In contrast to the well-documented primary leptomeningeal astrocytomas, primary leptomeningeal oligodendrogliomas (PLO) are rare with only three previously reported cases without parenchymal involvement [5–7]. We report a fourth case of PLO in this paper.