Basilar bifurcation aneurysms associated with persistent primitive hypoglossal artery

We report two cases of ruptured basilar bifurcation aneurysm associated wit h a persistent primitive hypoglossal artery. Angiograms revealed low-positi oned aneurysms; in both cases bilateral vertebral arteries and posterior co mmunicating arteries were hypoplastic or aplastic. Both aneurysms were succ essfully clipped via subtemporal transtentorial approach through the cranio tomy ipsilateral to the side of the primitive hypoglossal artery. The ipsil ateral craniotomy and exposure of the cervical carotid artery were helpful for obtaining the proximal control of the basilar artery needed to perform the clipping procedure with safety.