Posterior Inferior Cerebellar Artery Thrombosed Aneurysm Associated with Persistent Primitive Hypoglossal Artery Successfully Treated with Condylar Fossa Approach

A 68-year-old woman presented with generalized seizure due to the left internal carotid artery (ICA) aneurysmal compression of the ipsilateral medial temporal lobe. Computed tomography angiography (CTA) revealed multiple aneurysms of the right persistent primitive hypoglossal artery (PPHA), the right ICA, and the right anterior cerebral artery (ACA). The right PPHA originated from the ICA at the level of the C1 and C2 vertebral bodies and passed through the hypoglossal canal (HC). The PPHA aneurysm was large and thrombosed, which was located at the bifurcation of the right PPHA and the right posterior inferior cerebellar artery (PICA), projecting medially to compress the medulla oblongata. Since this patient had no neurological deficits, sequential imaging studies were performed to follow this lesion, which showed gradual growth of the PPHA aneurysm with further compression of the brain stem. Although the patient remained neurologically intact, considering the growing tendency clipping of the aneurysm was performed. Drilling of the condylar fossa was necessary to expose the proximal portion of the PPHA inside the HC. The key of this surgery was the preoperative imaging studies to fully understand the anatomical structures. The PPHA was fully exposed from the dura to the corner its turning inferiorly without damaging the occipital condylar facet. Utilizing this technique, the neck ligation of the aneurysm was safely achieved without any surgical complications.