title: Delineation of the safe zone in surgery of sylvian insular triangle:  morphometric analysis and magnetic resonance imaging study.
abstract: BACKGROUND
  Surgery within the insula carries significant risk of morbidity, particularly hemiparesis, because of the difficulty in detecting the internal capsule boundaries.
  
  
  OBJECTIVE
  We analyzed the anatomy of the insula and identified landmarks anticipated to facilitate surgery for intrinsic insular lesions.
  
  
  METHODS
  Insular region anatomy was studied in 11 cadaveric brains harvested within 72 hours postmortem. MRI of the specimens was acquired using 3.0 T with T2-weighting and 25 directions of diffusion tensor imaging. Landmarks easily recognizable during surgery were identified on the surface of the insula. The interrelationships between surface landmarks and critical structures were analyzed.
  
  
  RESULTS
  The posterior inferior insular point (PIIP) and the upper central insular point (UCIP) were newly established as landmarks on the insula. The PIIP corresponded to the obvious bend in the posterior long insular gyrus. The UCIP is the meeting point between the central insular sulcus and superior peri-insular sulcus. The corticospinal tract was identified as a high-intensity area in the posterior limb of the internal capsule on T2-weighted imaging and its course confirmed with diffusion tensor imaging tractography. The corticospinal tract took a course deep to the posterosuperior insula on T2-weighted imaging, 4.8 mm from the UCIP and 6.2 mm from the PIIP.
  
  
  CONCLUSIONS
  The posterosuperior part of the insula forms the region at greatest risk to corticospinal tract injury. The PIIP and UCIP are crucial to understanding the relationship of the insula with the posterior limb of the internal capsule including the corticospinal tract.
authors.affiliation: Department of Neurosurgery, West Virginia University, Morgantown, West Virginia, USA. nobuchaka32@hotmail.co.jp
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kaneko
authors.forename: Warren W
authors.initials: WW
authors.lastname: Boling
authors.forename: Takaharu
authors.initials: T
authors.lastname: Shonai
authors.forename: Kazumi
authors.initials: K
authors.lastname: Ohmori
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Shiokawa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kurita
authors.forename: Takanori
authors.initials: T
authors.lastname: Fukushima
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping / Q000009:adverse effects / Q000379:methods; D002102:Cadaver; D002540:Cerebral Cortex / Q000601:surgery*; D056324:Diffusion Tensor Imaging / Q000009:adverse effects / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000009:adverse effects / Q000379:methods*; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control / Q000601:surgery