title: Predicting the presigmoid retrolabyrinthine space using a sigmoid sinus tomography classification: A cadaveric study.
abstract: BACKGROUND
  The presigmoid retrolabyrinthine space is characterized by a widely variable size. The main structure involved in this large variability is the sigmoid sinus. Few studies have attempted to establish a reliable classification of sigmoid sinus to predict the presigmoid retrolabyrinthine space. We used tomographic mapping of human cadaver temporal bones to classify the position of sigmoid sinus and performed a cadaveric study to assess the validity of a novel classification in predicting the presigmoid retrolabyrinthine space.
  
  
  METHODS
  Ten human cadaver temporal bones were randomly selected and subjected to fine-cut computed tomography scanning to classify the position of sigmoid sinus using a reference line. The specimens were classified into medial and lateral groups and each specimen was then subjected to mastoidectomy. The groups were compared using quantitative and qualitative analysis.
  
  
  RESULTS
  The medial group showed a larger distance between the sigmoid sinus and the external auditory canal and a shallower lateral semicircular canal. In the lateral group, the mastoidectomy was more demanding, and the Trautmann's triangle was typically narrower and often "hidden" medially to the sigmoid sinus.
  
  
  CONCLUSIONS
  The tomographic classification proposed in this study predicts, in a cadaveric model, the presigmoid retrolabyrinthine space. It may help the surgeon select the best approach to reach the petroclival region and lead to safer neurological and otological surgeries.
authors.affiliation: Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: José Orlando
authors.initials: JO
authors.lastname: de Melo
authors.affiliation: Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: João
authors.initials: J
authors.lastname: Klescoski
authors.affiliation: Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: Cristian Ferrareze
authors.initials: CF
authors.lastname: Nunes
authors.affiliation: Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: Gustavo Augusto Porto Sereno
authors.initials: GA
authors.lastname: Cabral
authors.affiliation: Chairman of the Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: Mário Alberto
authors.initials: MA
authors.lastname: Lapenta
authors.affiliation: Professor and Chairman of the Department of Neurosurgery, Fluminense Federal University, Niterói, and Professor of the Department of Neurosurgery, Galeão Air Force Hospital, Rio de Janeiro, Brazil.
authors.forename: José Alberto
authors.initials: JA
authors.lastname: Landeiro
keywords: Presigmoid approach; posterior petrosal approach; retrolabyrinthine approach; sigmoid sinus; temporal bone; trautmann's triangle