Primary intracranial leptomeningeal glioma with persistant hypoglycorrhachia.

Metastatic involvement of the leptomeninges by malignant gliomas, such as glioblastoma multiforme and medulloblastoma, is not unusual. However, gliomas grossly appearing to arise in the lepto-meninges are rare, and may assume one of two forms: (1) the meningeal tumour may be entirely extracerebral and have no demonstrable connexion with the underlying neuraxis, or (2) it may grow largely in the subarachnoid space, but with definite connexions to the superficial layers of the adjacent cortex. An example of the second type is offered in the present case, where a well-differentiated astro-cytoma was grossly identifiable only in the sub-arachnoid space of the right Sylvian fissure, but microscopically it extended into the cerebral peri-vascular spaces and invaded the cerebral cortex through breaks in the adventitia-glia membranes.