title: A 3-dimensional computed tomographic procedure for planning retrosigmoid craniotomy.
abstract: OBJECTIVE
  The planning of retrosigmoid craniotomies often relies on anatomic landmarks on the posterolateral surface of the cranium, such as the asterion. However, the location of the asterion is not fixed with respect to the underlying transverse-sigmoid sinus complex. We introduce a simple procedure that uses 3-dimensional (3D) computed tomographic imaging to project the transverse-sigmoid sinus complex onto the external surface of the cranium.
  
  
  METHODS
  We enrolled 8 patients scheduled for retrosigmoid craniotomy (Group 1) and 30 patients without posterior fossa lesions (Group 2). The procedure consists of 3 steps: 1) marking the sinus on the internal surface on 3D images of the cranium, 2) transferring the marks to the external surface on axial images, and 3) checking the transferred marks on the external surface of the cranium on 3D images.
  
  
  RESULTS
  In Group 1, the craniotomies planned with the aid of our procedure coincided with findings made at surgery, indicating the accuracy of our procedure. When we applied it in morphometric studies in Group 2, we found that the relative location of the transverse-sigmoid sinus junction to the asterion, the superior nuchal line, and the posterior edge of the mastoid process exhibited a high degree of individual variation.
  
  
  CONCLUSIONS
  Retrosigmoid craniotomy standardized according to anatomic landmarks raises the risk for sinus injury because of variations in their location. We offer our 3D computed tomographic imaging-based procedure as a useful device for the planning of safer retrosigmoid craniotomies.
authors.affiliation: Department of Neurosurgery, Kumamoto University Medical School, Kumamoto, Japan. thamasaki- nsu@umin.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hamasaki
authors.forename: Motohiro
authors.initials: M
authors.lastname: Morioka
authors.forename: Hideo
authors.initials: H
authors.lastname: Nakamura
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Yano
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hirai
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Kuratsu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D003392:Cranial Sinuses / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D003399:Craniotomy / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D007431:Intraoperative Complications / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods*; D009777:Occipital Bone / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery; D011446:Prospective Studies; D019292:Skull Base Neoplasms / Q000601:surgery; D012984:Software; D013701:Temporal Bone / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014277:Trigeminal Neuralgia / Q000601:surgery; D055815:Young Adult
chemical_list: D015415:Biomarkers