title: Image-guided lateral suboccipital approach: part 1-individualized landmarks for surgical planning.
abstract: OBJECTIVE
  Being situated close to the transverse and sigmoid sinus, the asterion has traditionally been viewed as a landmark for surgical approaches to the posterior fossa. Cadaveric studies, however, have shown its variability in relation to underlying anatomic structures. We have used an image-guidance technology to determine the precise anatomic relationship between the asterion and the underlying transverse-sigmoid sinus transition (TST) complex in patients scheduled for posterior fossa surgery. The applicability of three-dimensional (3-D) volumetric image-rendering for presurgical anatomic identification and individualization of a surgical landmark was evaluated.
  
  
  METHODS
  One-millimeter computed tomographic slices were combined with venous computed tomographic angiography in 100 patients, allowing for 3-D volumetric image-rendering of the cranial bone and the dural vasculature at the same time. The spatial relationship between the asterion and the TST was recorded bilaterally by using opacity modulation of the bony surface. The location of both the asterion and the TST could be confirmed during surgery in all of these patients.
  
  
  RESULTS
  It was possible to accurately visualize the asterion and the sinuses in a single volumetrically rendered 3-D image in more than 90% of the patients. The variability in the anatomic position of the asterion as shown in cadaveric studies was confirmed, providing an individualized landmark for the patients. In this series, the asterion was located from 2 mm medial to 7 mm lateral and from 10 mm inferior to 17 mm superior to the TST, respectively.
  
  
  CONCLUSIONS
  Volumetric image-rendering allows for precise in vivo measurements of anatomic distances in 3-D space. It is also a valuable tool for assessing the validity of traditional surgical landmarks and individualizing them for surgical planning.
authors.affiliation: Department of Neurosurgery, University Hospital Tübingen, Charlottenstr. 37/1, 72070 Tübingen, Germany. alireza.gharabaghi@uni-tuebingen.de
authors.forename: Alireza
authors.initials: A
authors.lastname: Gharabaghi
authors.forename: Steffen K
authors.initials: SK
authors.lastname: Rosahl
authors.forename: Günther C
authors.initials: GC
authors.lastname: Feigl
authors.forename: Thomas
authors.initials: T
authors.lastname: Liebig
authors.forename: Javad M
authors.initials: JM
authors.lastname: Mirzayan
authors.forename: Stefan
authors.initials: S
authors.lastname: Heckl
authors.forename: Ramin
authors.initials: R
authors.lastname: Shahidi
authors.forename: Marcos
authors.initials: M
authors.lastname: Tatagiba
authors.forename: Madjid
authors.initials: M
authors.lastname: Samii
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002533:Cerebral Angiography / Q000379:methods*; D002648:Child; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000000981:diagnostic imaging* / Q000601:surgery*; D011300:Preoperative Care / Q000379:methods; D013382:Subtraction Technique; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*