CT
Non-contrast CT head
extensive bilateral subarachnoid hemorrhage - perimesencephalic; in all the basal cisterns; in the narrowed third ventricle, Sylvian aqueduct, and fourth ventricle; in the premedullary cistern; in the Sylvian cisterns and fissures; in the interhemispheric fissure; and bifrontal
the temporal horns of the lateral ventricles are dilated - early sign of hydrocephalus
the cerebral and cerebellar sulci are effaced - suggestive of brain edema
CT angiogram
pedunculated aneurysm with a "nipple" at the basilar tip measuring 3 mm in diameter and 5.5 mm in length, deviating to the left P1
the intracranial arteries appear slightly narrowed, perhaps due to cerebral edema
the neck arteries are patent