Introduction

Primary diffuse leptomeningeal gliomatosis is a rare neoplasm defined by the infiltration of the subarachnoid spaces by glial neoplastic cells, without there being a detectable intra-axial glioma. Unlike the meningeal dissemination of glial tumour cells that might follow a previously diagnosed parenchymatous glioma, primary diffuse leptomeningeal gliomatosis probably originates from heterotopic leptomeningeal glial nests in the subarachnoid space. Its clinical symptoms usually result from intracranial hypertension and malignant invasion of cranial or spinal nerves. Cranial and spinal MRI imaging usually shows extensive leptomeningeal thickening with gadolinium enhancement. Cerebrospinal fluid (CSF) cytology generally fails to detect malignant cells and so a meningeal biopsy—guided by the MRI findings—is often needed to confirm the diagnosis.

Among about 80 reported cases of primary diffuse leptomeningeal gliomatosis, six involved the spinal cord1; in these, the presenting symptoms, such as limb weakness and back pain, suggested a likely spinal cord location. Here, we report a patient with encephalopathic symptoms who had no intracranial meningeal enhancement on her brain MRI, either at the start or during the disease course, despite having spinal cord meningeal enhancement. We confirmed the diagnosis of primary diffuse leptomeningeal gliomatosis by identifying glial malignant cells in the CSF after the third spinal tap.