Endoscopic transsphenoidal surgery for a somatotroph pituitary neuroendocrine tumor associated with an infraoptic course of the anterior cerebral artery: A case report

Background: Identifying cerebrovascular anomalies before neurosurgical procedures is essential to avoid intraoperative complications. An infraoptic course of the anterior cerebral artery (IOA) is a rare variant in which the anterior cerebral artery (ACA) arises near the ophthalmic artery and passes beneath the optic nerve. Despite numerous reports of cerebral aneurysms coexisting with IOA, reports of coexistence with brain tumors are extremely rare, and no studies have reported endoscopic transsphenoidal surgery (eTSS) performed for pituitary tumors. Failure to recognize this IOA anomaly preoperatively is critical owing to the risk of vascular injury. Case Description: A 47-year-old man presented with acromegaly caused by a somatotroph pituitary neuroendocrine tumor. Magnetic resonance imaging (MRI) revealed a sellar–suprasellar mass, and biochemical testing confirmed excess growth hormone production. After lanreotide-induced tumor shrinkage, surgical treatment was planned. Preoperative MRI, computed tomography angiography, and three-dimensional (3D) fusion imaging demonstrated bilateral IOA and duplication of the left A1 segment. These images enabled a detailed assessment of the tumor, pituitary gland, and vascular anatomy, suggesting that extracapsular resection via eTSS can be safely performed. Intraoperatively, the IOA adhered to the dura as predicted. Total tumor resection was achieved without vascular injury. Postoperative MRI confirmed complete removal, and hormone levels were normalized. Conclusion: IOA is an exceptionally rare vascular anomaly, and unrecognized cases may lead to severe intraoperative complications. This case highlights the importance of meticulous preoperative imaging, particularly 3D fusion techniques, for IOA identification and safe eTSS planning for functional pituitary tumors.