title: Endoscopic endonasal surgery for petrous apex lesions.
abstract: BACKGROUND
  Endoscopic endonasal approaches to the ventral skull base are categorized based on their orientation in coronal and sagittal planes. For all of these approaches, the sphenoid sinus is the starting point, and provides orientation to important vascular and neural structures. Surgical approaches to the petrous apex include 1) a medial approach, 2) a medial approach with internal carotid artery (ICA) lateralization, and 3) a transpterygoid infrapetrous approach (inferior to the petrous internal carotid artery). The choice of a surgical approach depends on the relationship of the lesion to the internal carotid artery (medial or inferior), degree of medial expansion, and pathology. The purpose of this paper is to discuss the anatomic and technical features of endoscopic surgical approaches to the petrous apex, provide a new classification for approaches that focuses on the relationship of the lesion to the petrous internal carotid artery, and provide outcomes data on our first 20 endoscopic petrous apex approaches.
  
  
  METHODS
  A retrospective clinical outcome study of endoscopic petrous apex surgeries was performed at the University of Pittsburgh Medical Center. The medical records from patients with endoscopic endonasal approaches to isolated petrous apex lesions were reviewed for demographics, diagnoses, presentation, endoscopic approach, and clinical outcomes. Patients with lesions that extended into the petrous apex but were not isolated to the petrous apex were excluded (e.g., clival chordoma with extension into the petrous apex).
  
  
  RESULTS
  Twenty patients were included in the analysis: 13 inflammatory cystic lesions (9 cholesterol granulomas and four petrous apicitis) and 7 solid lesions. Chondrosarcoma was the most common solid petrous apex lesion in our series. Twelve of 13 cystic lesions were drained endoscopically (one surgery was aborted early in the series). All drained patients had resolution of presenting symptoms. One patient had closure of the outflow tract without return of symptoms and one patient had revision endoscopic drainage due to scarring and neo-osteogenesis and return of unilateral headache. No carotid injuries and no new cranial neuropathies occurred perioperatively. The advantages and limitations of the medial transsphenoidal approaches (with and without carotid mobilization) and the transpterygoid infrapetrous approach are discussed.
  
  
  CONCLUSIONS
  The endoscopic endonasal approach to petrous apex lesions is safe and effective for appropriately selected patients in the hands of experienced endoscopic skull base surgeons. If offers advantages of removing the hearing and facial nerve risks from the transtemporal/transcranial approaches and allows for a larger and more natural drainage pathway into the sinuses.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, University of North Carolina Memorial Hospitals, Chapel Hill, North Carolina, USA.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Zanation
authors.forename: Carl H
authors.initials: CH
authors.lastname: Snyderman
authors.forename: Ricardo L
authors.initials: RL
authors.lastname: Carrau
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gardner
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Prevedello
authors.forename: Amin B
authors.initials: AB
authors.lastname: Kassam
mesh_terms: D004322:Drainage / Q000379:methods; D004724:Endoscopy; D006801:Humans; D010579:Petrous Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D012189:Retrospective Studies; D019291:Skull Base / Q000000981:diagnostic imaging / Q000601:surgery*; D019292:Skull Base Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D013101:Sphenoid Sinus / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome