title: Intended Near-Total Removal of Koos Grade IV Vestibular Schwannomas: Reconsidering the Treatment Paradigm.
abstract: The goals of treating Koos grade IV vestibular schwannomas are to relieve brainstem compression, preserve or restore neurological function, and achieve long-term tumor control while minimizing tumor- and treatment-related morbidity.
  
  
  
  To propose a treatment paradigm involving the intentional near-total removal of Koos grade IV vestibular schwannomas, in which a small amount of residual tumor is not dissected off the cisternal portion of the facial nerve. Patients are then followed by a wait-and-scan approach. Any subsequent volumetric progression of the residual tumor is treated with radiosurgery.
  
  
  
  This is a case series of 44 consecutive unselected patients who underwent intended near-total resection of a Koos grade IV vestibular schwannoma through a retrosigmoid approach from January 2009 to December 2015. Pre- and postoperative volumetric analyses were performed on routine magnetic resonance imaging sequences (constructive interference in steady state and gadolinium-enhanced T1-weighted sequence).
  
  
  
  The mean preoperative tumor volume was 10.9 cm3. The mean extent of resection was 89%. At the last clinical follow-up, facial nerve function was good [House and Brackmann (HB) I-II] in 89%, fair (HB III) in 9%, and poor (HB IV-VI) in 2% of the patients. At the last radiological follow-up, the residual tumor had become smaller or remained the same size in 84% of patients. Volumetric progression was negatively correlated with the original extent of resection and positively correlated with postoperative residual tumor volume (P = .01, P < .001, respectively).
  
  
  
  Intended near-total removal results in excellent preservation of facial nerve function and has a low recurrence rate. Any progressive residual tumor may be treated by radiosurgery.
authors.affiliation: Department of Neurosurgery, Basel University Hospital, Basel, Switzerland.|Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, Basel University Hospital, Basel, Switzerland.
authors.forename: Daniel Walter
authors.initials: DW
authors.lastname: Zumofen
authors.affiliation: Faculty of Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Guffi
authors.affiliation: Department of Biomedicine, Basel University Hospital, Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Epple
authors.affiliation: Department of Neurosurgery, Basel University Hospital, Basel, Switzerland.
authors.forename: Birgit
authors.initials: B
authors.lastname: Westermann
authors.affiliation: Department of Neurosurgery, Bern University Hospital, Bern, Switzerland.
authors.forename: Anna-Katharina
authors.initials: AK
authors.lastname: Krähenbühl
authors.affiliation: Department of Neurosurgery, Basel University Hospital, Basel, Switzerland.
authors.forename: Susanne
authors.initials: S
authors.lastname: Zabka
authors.affiliation: Department of Neurosurgery, Basel University Hospital, Basel, Switzerland.
authors.forename: Ethan
authors.initials: E
authors.lastname: Taub
authors.affiliation: Department of Otolaryngology, Basel University Hospital, Basel, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bodmer
authors.affiliation: Department of Neurosurgery, Basel University Hospital, Basel, Switzerland.
authors.forename: Luigi
authors.initials: L
authors.lastname: Mariani
mesh_terms: D000328:Adult; D000368:Aged; D020220:Facial Nerve Injuries / Q000517:prevention & control; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Facial nerve outcome; Facial nerve preservation surgery; Intended near-total resection; Koos grade IV; Vestibular schwannoma