title: Surgical Freedom Evaluation During Optic Nerve Decompression: Laboratory Investigation.
abstract: OBJECTIVE
  Various surgical routes have been used to decompress the intracanalicular optic nerve. Historically, a transcranial corridor was used, but more recently, ventral approaches (endonasal and/or transorbital) have been proposed, individually or in combination. The present study aims to detail and quantify the amount of bony optic canal removal that may be achieved via transcranial, transorbital, and endonasal pathways. In addition, the surgical freedom of each approach was analyzed.
  
  
  METHODS
  In 10 cadaveric specimens (20 canals), optic canals were decompressed via pterional, endoscopic endonasal, and endoscopic superior eyelid transorbital corridors. The surgical freedom and circumferential optic canal decompression afforded by each approach was quantitatively analyzed. Statistical comparison was carried using a nonpaired Student t test.
  
  
  RESULTS
  An open pterional transcranial approach allowed the greatest area of surgical freedom (transcranial, 109.4 ± 33.6 cm2; transorbital, 37.2 ± 4.9 cm2; endonasal homolateral, 10.9 ± 5.2 cm2; and endonasal contralateral, 11.1 ± 5.6 cm2) with widest optic canal decompression compared with the other 2 ventral routes (transcranial, 245.2; transorbital, 177.9; endonasal, 144.6). These differences reached, in many cases, statistical significance for the transcranial approach.
  
  
  CONCLUSIONS
  This anatomic contribution provides a comprehensive evaluation of surgical access to the optic canal via 3 distinct, but complementary, approaches: transcranial, transorbital, and endonasal. Our results show that, as expected, a transcranial approach achieved the widest degree of circumferential optic canal decompression and the greatest surgical freedom for manipulation of surgical instruments. Further surgical experience is necessary to determine the proper surgical indication for the transorbital approach to this disease.
authors.affiliation: Division of Neurosurgery, School of Medicine and Surgery, Universita degli Studi di Napoli Federico II, Naples, Italy. Electronic address: albertodisomma87@gmail.com.
authors.forename: Alberto
authors.initials: A
authors.lastname: Di Somma
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Comprehensive Stroke Center at UC Neuroscience Institute, Mayfield Clinic, Cincinnati, Ohio, USA.
authors.forename: Norberto
authors.initials: N
authors.lastname: Andaluz
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Comprehensive Stroke Center at UC Neuroscience Institute, Mayfield Clinic, Cincinnati, Ohio, USA.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Gogela
authors.affiliation: Division of Neurosurgery, School of Medicine and Surgery, Universita degli Studi di Napoli Federico II, Naples, Italy.
authors.forename: Luigi Maria
authors.initials: LM
authors.lastname: Cavallo
authors.affiliation: Department of Neurosurgery, University of Cincinnati College of Medicine, Comprehensive Stroke Center at UC Neuroscience Institute, Mayfield Clinic, Cincinnati, Ohio, USA.
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Keller
authors.affiliation: Laboratory of Surgical Neuroanatomy, Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Prats-Galino
authors.affiliation: Division of Neurosurgery, School of Medicine and Surgery, Universita degli Studi di Napoli Federico II, Naples, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Cappabianca
mesh_terms: D000328:Adult; D002102:Cadaver; D019299:Decompression, Surgical / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D044583:Neuroendoscopy / Q000379:methods*; D019635:Neurosurgical Procedures / Q000379:methods; D009900:Optic Nerve / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*
keywords: Endoscopic endonasal; Endoscopic transorbital; Optic nerve; Quantitative analysis; Surgical freedom; Transcranial optic nerve decompression