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

3-month follow-up MRI:

• MRA: filling defect between basilar tip and left PCA, representing the embolization coils in the aneurysm

• no evidence of new aneurysm

• SWI: blood degradation products on the tentorial leaflets and in the basal cisterns, as well as small amount mainly in the biparietal sulci and bifrontal sulci around the vertex

• two tiny foci of susceptibility artifact in the right cerebellar hemisphere and one in the left hemisphere

• above the tentorium: several nonspecific abnormal white matter foci on the right, single one on the left - probably representing microangiopathy

• no abnormal port-contrast enhancement