Surgical Treatment of a Double Origin Posterior Inferior Cerebellar Artery Aneurysm and Insights From Embryology: Case Report and Literature Review. 
Aneurysms affecting double origin (DO) posterior inferior cerebellar artery (PICA) variants are rare.  Most reports describe endovascular occlusion of the affected branch to treat the aneurysm, but we describe a patient in which open surgical sacrifice of 1 branch resulted in insufficient perfusion.  We report the only case of open surgical treatment of an aneurysm affecting a leg of a DOPICA.  A 42-year-old woman presenting with the worst headache of her life was found to have a DOPICA aneurysm and initially treated by trapping the aneurysm.  Intraoperative indocyanine green imaging revealed insufficient perfusion through the caudal branch, which was remediated by end-to-end anastomosis to preserve flow through both origins.  The patient made a full recovery.  Treating a DOPICA aneurysm by sacrificing 1 of the origins is not possible for all patients.  This first report of open surgical treatment of a DOPICA leg aneurysm suggests that 1 or both branches may be required for sufficient perfusion, and the unique embryology of DOPICA development suggests a possible mechanism.