en MIS MIS Case Report Case Report Introduction: Epidermoid tumors comprise 1% of intracranial tumors. Although reported,<br> intraosseous epidermoid tumors are even more rare. Cystic lesions of the petrous apex<br> are uncommon and surgically challenging; the most rare pathology is presumed to be<br> epidermoid.<br> Case Presentation: This is a case of a 61-year-old woman with a large skull-base tumor extending<br> inferiorly from the C1-C2 articulation and superiorly to the tuberculum sella.<br> The lesion replaced the left-sided petrous apex, and the lateral extension of the tumor<br> reached the styloid process. The tumor displayed intradural invasion medial to the internal<br> auditory meatus, producing an intra-axial mass at the level of the upper pons.<br> The patient presented with a 4-month history of headache and total unilateral deafness.<br> Under image guidance, an endoscopic endonasal approach was used to totally resect the<br> tumor. By following the tumor&rsquo;s dural defect, the intra-axial part of the tumor was safely<br> resected, and the dural defect was successfully repaired.<br> Conclusions: Image-guided endoscopic endonasal surgery is a versatile approach that<br> can safely and easily address a large epidermoid tumor in this challenging region, obviating<br> the need for demanding and sophisticated transcranial surgery. Epidermal Cyst Endoscopic Endonasal Skull Base Surgery, Computer-Assisted 0 0 http://annbsurg.iums.ac.ir/browse.php?a_code=A-10-31-237&slc_lang=en&sid=1 Maryam Jalessi 1003194753284600609 1003194753284600609 No 1 Endoscopic Skull Base Surgery Unit, ENT-Head and Neck Research Center and Department, Hazrat Rasoul Akram Hospital, Tehran University of Medical Sciences, Tehran, IR Iran Guive Sharifi 1003194753284600610 1003194753284600610 Yes 2 Neurosurgery Department, Loghman Hakim Hospital, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran Ali Ahmadvand 1003194753284600611 1003194753284600611 No 3 Neurosurgery Department, Imam Reza Hospital, Tabriz University of Medical Sciences, Tabriz, IR Iran Rozita Jafari 1003194753284600612 1003194753284600612 No 4 ENT, Head and Neck Department, Imam Reza Hospital, Tabriz University of Medical Sciences, Tabriz, IR Iran Sahar Zahedi 1003194753284600613 1003194753284600613 No 1 Endoscopic Skull Base Surgery Unit, ENT-Head and Neck Research Center and Department, Hazrat Rasoul Akram Hospital, Tehran University of Medical Mohammad Farhadi 1003194753284600614 1003194753284600614 No 1 Endoscopic Skull Base Surgery Unit, ENT-Head and Neck Research Center and Department, Hazrat Rasoul Akram Hospital, Tehran University of Medical