A female in her 70s with a history of hypertension and hyperlipidemia developed the sudden-onset of headache and slurred speech followed by unresponsiveness. Initial computed tomography (CT) imaging revealed a Fisher Grade 4 subarachnoid hemorrhage. There was prominent blood in the suprasellar, pre-pontine, and left perimesencephalic cisterns with an intraparenchymal component extending to the left thalamus, midbrain, and cerebellum. On transfer to our institution, her neurological examination was poor with evidence of a weak cough reflex and flexion of the lower extremities to painful stimulus. After the placement of an external ventricular drain for the treatment of acute hydrocephalus, she underwent a diagnostic cerebral angiogram which revealed a multilobular left P2 aneurysm measuring 8.0 mm in maximum dimension []. There was a fetal origin of the left PCA. During catheter angiography for endovascular coiling, left internal carotid artery (ICA) angiogram showed a PPTA supplying the distal half of the BA, including the SCAs bilaterally and the right PCA but not the left PCA, which had a fetal origin. The proximal half of the BA up to the AICA-posterior inferior cerebellar artery (PICA) complexes was isolated from the distal half by a mid-basilar atresia and was fed exclusively from the right vertebral artery (VA). The left VA was hypoplastic. Despite successful aneurysm coiling, the patient did not have significant clinical improvement. Given her persistent poor neurological examination over the next several days, the family decided to pursue comfort care measures. The patient ultimately expired on hospital day 2.