A novel method of identifying the internal acoustic canal in the middle fossa approach in a cadaveric study - The rule of 2s

Raghuram Sampath, Chad Glenn, Shashikant Patil, Prasad Vannemreddy, Lawrence Gardner, Anil Nanda, Bharat Guthikonda

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Objective: Multiple landmarks and anatomic relationships exist to identify internal acoustic canal (IAC) in middle fossa approach for removing intracanalicular schwannomas. We attempted to identify a reproducible, practical method to quickly identify the IAC that would be applicable when an expanded middle fossa approach is required. Design: Middle fossa approach was performed on 10 cadavers (21 dissections). In the first head, temporal and suboccipital craniotomies were performed to identify landmarks and formulate a hypothesis. Porous acusticus (PA) was identi fied and IAC was circumferentially skeletonized into middle fossa. Orientation of IAC in the middle fossa was evaluated in relation to foramen spinosum (FS), foramen ovale (FO), petrous ridge, and petrous apex. Consistency of this relationship was tested in the remaining heads. Results: The opening of PA (point A) was consistently found at a mean of 2.38 cm posterolateral to the petrous apex along the petrous ridge (range 2.1 to 2.8). A line was drawn from the FO to FS and extrapolated posteriorly. The IAC (point B) was found a mean distance of 2.39 cmfrom FS along the FS-FO line (range 2.1 to 2.8). The course of IAC was consistently found by connecting point A to point B. Conclusion: A novel, practical, and reproducible method is described to identify the IAC via the expanded middle fossa approach.

Original languageEnglish (US)
Pages (from-to)253-260
Number of pages8
JournalJournal of Neurological Surgery, Part B: Skull Base
Volume73
Issue number4
DOIs
StatePublished - Aug 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Clinical Neurology

Keywords

  • Foramen ovale
  • Foramen spinosum
  • Internal acoustic canal
  • Middle fossa
  • Petrous apex

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