title: Tentorial incision in a lateral-medial direction with minimal retraction of the temporal lobe in the subtemporal transtentorial approach to the middle tentorial incisural space.
abstract: OBJECTIVE
  The subtemporal transtentorial approach provides excellent exposure of the middle incisural space. A modification of the subtemporal transtentorial approach with use of a partial mastoidectomy is presented to avoid damage to the temporal lobe as a result of retraction as well as damage to venous structures.
  
  
  METHODS
  Four patients, one with a superior cerebellar artery aneurysm, one with a metastatic tumor in the midbrain, one with a tentorial meningioma, and one with a tentorial schwannoma were treated with the present approach. After subtemporal craniotomy, all of the cortical bone overlying the mastoid was removed. The mastoid air cells were drilled down, and the upper part of Trautman's triangle was exposed above the level of the lateral semicircular canal. The presigmoid dura and the temporal dura were opened and connected by incising the superior petrosal sinus. The cerebellar tentorium was incised in a lateral-medial direction along the angle of the tentorium.
  
  
  RESULTS
  In each case, the tentorium was incised with minimal retraction of the temporal lobe without any damage to the temporal lobe, or venous structures. The present approach yielded excellent visualization of the lesion and adjacent neurovascular structures. In 3 of 4 cases, the lesions were successfully treated. In the patient with a tentorial schwannoma extending from the middle to posterior incisural space, the extreme lateral supracerebellar-infratentorial approach was combined with the present approach.
  
  
  CONCLUSIONS
  Although additional partial mastoidectomy is time-consuming, it reduces the risk of damage to the temporal lobe as a result of retraction as well as damage to venous structures.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Toyama, Toyama, Japan. nakamasa@iwa.att.ne.jp
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: M
authors.initials: M
authors.lastname: Kurimoto
authors.forename: S
authors.initials: S
authors.lastname: Nagai
authors.forename: H
authors.initials: H
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Hori
authors.forename: S
authors.initials: S
authors.lastname: Endo
mesh_terms: D000328:Adult; D000368:Aged; D020295:Brain Stem Neoplasms / Q000601:surgery; D003399:Craniotomy / Q000379:methods*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000601:surgery; D008297:Male; D008416:Mastoid / Q000601:surgery; D008577:Meningeal Neoplasms / Q000601:surgery; D008579:Meningioma / Q000601:surgery; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D009442:Neurilemmoma / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D013702:Temporal Lobe / Q000601:surgery*