Aqueductal (pencil) glioma presenting as neurogenic pulmonary edema: a case report. A case of neurogenic pulmonary edema due to hydrocephalus, without initial neurological deficit, is described. Computed tomography demonstrated a ring enhancing lesion in the tectum of the mesencephalon obstructing the aqueduct of Sylvius. The lesion, on autopsy, was a rare mesencephalic glioma described in the literature as a "pencil glioma" of the aqueduct. 