Unusual manifestation of vein of Galen aneurysm.

A 62-year-old man was seen with an exc ruciat ing headache of a few hours duration. Th e headache was predominantly occipital but extended to the frontal and temporal reg ions. He also complained of nausea, vomiting, and diplopia . His med ical history was unremarkable except for hypertension , which was controlled with medication . Physical examination revealed a blood pressure of 170/ 80 mm Hg . There was slight nuchal rigidity . Except for diplopia, no other cranial nerve dysfunction was evident . He was stuporous but easily arousable. The admitting diagnosis was cerebrovascular accident with possible pontine hemorrhage. Cranial computed tomography (CT) showed a midline high density in th e posterior third ventricular region or pineal gland. After intravenous infusion of 75 ml of Renografin 60 (diatrizoate meglumine, 22 g iodine), CT revealed enhancement of the mass by about 20 Hounsfield numbers (H) (figs . 1 A and 1 B). Hydrocephalus involving the lateral and third ventricles was present . Periventricu lar low density was present around the anterior horns. There was no evidence of blood in the subarachnoid spaces. Shortly after admission, the patient became comatose. Lumbar pu ncture was consistent wi th recent subarachnoid hemorrhage. Although the CT findings were those of a posterior third ventricular mass lesion, angiog raphy was performed because of th e c linical and cerebrospinal fluid findings that indicated subarachnoid hemorrhage. The right carotid angiogram was normal. Th e left carotid angiogram revealed prompt opac ificat ion (less than 1 sec after injec tion of contrast medium) of an aneurysm measuring 1 .5 cm in diameter in the reg ion of the vein of Galen. The predominant vascular supply to the aneurysm was from hypertroph ied tentorial branches of the meningohypophyseal artery (fig. 1 C). Vertebral angiography revealed early visualizat ion of th e straight sinus with relatively faint opacification of the aneurysm, presumably supplied by the choroidal branches of th e left posterior cerebral artery . Over th e next several hours, his neurologic status improved. He was treated with steroids. A ventriculoperitoneal shun ting proce-