Endoscopic Endonasal Removal of a Large Petrous-Apex Epidermoid Tumor With Clival Involvement and Intradural Invasion

Introduction: Epidermoid tumors comprise 1% of intracranial tumors. Although reported, intraosseous epidermoid tumors are even more rare. Cystic lesions of the petrous apex are uncommon and surgically challenging; the most rare pathology is presumed to be epidermoid.\r\nCase Presentation: This is a case of a 61-year-old woman with a large skull-base tumor extending inferiorly from the C1-C2 articulation and superiorly to the tuberculum sella. The lesion replaced the left-sided petrous apex, and the lateral extension of the tumor reached the styloid process. The tumor displayed intradural invasion medial to the internal auditory meatus, producing an intra-axial mass at the level of the upper pons. The patient presented with a 4-month history of headache and total unilateral deafness. Under image guidance, an endoscopic endonasal approach was used to totally resect the tumor. By following the tumor’s dural defect, the intra-axial part of the tumor was safely resected, and the dural defect was successfully repaired. \r\nConclusions: Image-guided endoscopic endonasal surgery is a versatile approach that can safely and easily address a large epidermoid tumor in this challenging region, obviating the need for demanding and sophisticated transcranial surgery.