Ischemic Complications After Parent Artery Occlusion for Ruptured Posterior Cerebral Artery Aneurysm With a Fetal-Type Posterior Communicating Artery: A Case Report.

Posterior cerebral artery (PCA) aneurysms are uncommon, and many are considered to be dissecting aneurysms. In ruptured cases, parent artery occlusion (PAO) is often selected as a treatment strategy. However, the morphology of the posterior communicating artery (PCoA) may influence the risk of postoperative ischemic complications. We report the case of a 76-year-old man with a sudden-onset headache and impaired consciousness. He was diagnosed with subarachnoid hemorrhage (SAH) and Hunt and Kosnik grade V. Imaging revealed a ruptured aneurysm located in the distal P2 segment of the left PCA. The ipsilateral P1 segment was hypoplastic, and the PCA was mainly supplied via a fetal-type PCoA. To prevent rebleeding, PAO was performed via a PCoA approach. The aneurysm and the proximal PCA segment were embolized with coils. Although complete occlusion was achieved, postoperative magnetic resonance imaging (MRI) demonstrated infarctions in the lateral thalamus and the medial temporal and occipital lobes. These findings were consistent with ischemia in the territories of the thalamogeniculate artery and the temporal branches of the PCA. The patient developed right homonymous hemianopia and higher cortical dysfunction, including attention and memory impairment, and was transferred to a rehabilitation hospital with a modified Rankin Scale (mRS) score of 4. While PAO effectively prevented rebleeding in this case, this report suggests a possible association between fetal-type PCoA anatomy and ischemic complications after PAO. Careful treatment planning based on detailed preoperative vascular anatomical assessment is essential.