title: Endoscopic minimally invasive neurosurgery: emerging techniques and expanding role through an extensive review of the literature and our own experience - part II: extraendoscopic neurosurgery.
abstract: OBJECTIVE
  The field of minimally invasive neurosurgery has grown dramatically especially in the last decades. This has been possible, in the most part, due to the advancements in technology especially in tools such as the endoscope. The contemporary classification scheme for endoscopic procedures needs to advance as well.
  
  
  METHODS
  The present classification scheme for neuroendoscopic procedures has become confusing because it mainly describes the use of the endoscope as an assisting device to the microscope. The authors propose an update to the current classification that reflects the independence of the endoscope as a tool in minimally invasive neurosurgery.
  
  
  RESULTS
  The proposed classification groups the procedures as 'intraendoscopic' neurosurgery or 'extraendoscopic' neurosurgery (XEN) in relation to the 'axis' of the endoscope. A review of the literature for the XEN group together with exemplary cases is presented.
  
  
  CONCLUSIONS
  We presented our proposed classification for the endoscope-only surgical procedures. The XEN group is expanded in this article.
authors.affiliation: Department of Neurosurgery, Cleveland Clinic, Cleveland, OH, USA.
authors.forename: Xiao
authors.initials: X
authors.lastname: Di
authors.forename: Alan
authors.initials: A
authors.lastname: Sui
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Hakim
authors.forename: Maode
authors.initials: M
authors.lastname: Wang
authors.forename: Jan Peter
authors.initials: JP
authors.lastname: Warnke
mesh_terms: D016080:Arachnoid Cysts / Q000601:surgery; D001706:Biopsy / Q000379:methods; D001921:Brain / Q000473:pathology / Q000601:surgery; D002543:Cerebral Hemorrhage / Q000601:surgery; D006801:Humans; D044583:Neuroendoscopy / Q000145:classification; D019635:Neurosurgical Procedures; D010902:Pituitary Gland / Q000601:surgery; D019291:Skull Base / Q000601:surgery; D013131:Spine / Q000601:surgery