Abstract
BACKGROUND: Sphenopetroclival chondrosarcomas (SPCCs) typically present as paramidline lytic tumors. Bilateral disease or calcific degeneration is infrequent but associated with increased surgical morbidity and suboptimal removal when adhering to neurovascular structures. The endoscopic endonasal transclival approach (EETA) effectively accesses the retrocarotid space using angled instruments. The authors present the technical nuances of EETA for a large calcified SPCC with bilateral petrous apex involvement without utilizing a full transpterygoid approach or carotid mobilization. OBSERVATIONS: A 41-year-old male presented with chronic, nonspecific headaches. CT imaging revealed a large sclerotic-lytic mass in the upper-middle clival area involving both petrous apices. MRI showed anterior pontine compression, bilateral cavernous sinus involvement, and partial encasement of the left cavernous carotid artery (CCA). An EETA with bilateral anteromedial petrosectomy and transcavernous access was performed, and near-total resection was achieved. Histopathology confirmed a grade 1 conventional chondrosarcoma, and the patient subsequently underwent proton beam radiotherapy. Surveillance imaging showed stable residual attached to the left CCA and posterior clinoid process. LESSONS: EETA offers maximal safe resection of SPCC with bilateral anteromedial petrous apex involvement without the need for complex maneuvers that could jeopardize carotid arteries or vidian nerves. When judiciously planned, low recurrence rates are expected for low-grade tumors. https://thejns.org/doi/10.3171/CASE25119.