title: Bony tunnel formation in the middle meningeal groove: an anatomic study for safer pterional craniotomy.
abstract: OBJECTIVE
  When the bone flap is removed in a pterional craniotomy, the middle meningeal artery (MMA) should be gently dissected to minimize blood loss. However, when the MMA pierces a bony tunnel in the middle meningeal groove it is easily damaged upon bone flap elevation. We have performed an anatomic study of this tunnel to render pterional craniotomy safer.
  
  
  METHODS
  We examined 78 sides from 39 adult skulls for the presence and length of the tunnel, the distance between the lateral border of the superior orbital fissure and the proximal part of the tunnel, and examined the relationship between the MMA piercing the tunnel to a surface landmark, i.e., the junction of the sphenoparietal, sphenosquamosal, and squamosal sutures.
  
  
  RESULTS
  We found 59 tunnels on 78 sides (75.6%); 2 were at the branching of the MMA on one side. The tunnels were located on the temporal side of the lesser wing of the sphenoid bone. The length of the tunnel and the distance from the superior orbital fissure were 3-23 mm (mean: 12.2 mm) and 11-33 mm (mean: 18.9 mm), respectively. Most tunnels (86.4%) were bilateral; in 67.8% of the specimens the MMA piercing the tunnel was just beneath the surface landmark.
  
  
  CONCLUSIONS
  As we found a high incidence of bony tunnel formation in the middle meningeal groove, actual findings can be different from the accepted nomenclature. If a tunnel exists, the MMA is easily damaged upon cracking of the lesser wing during bone flap elevation. Recognition of this anatomy may render pterional craniotomy safer.
authors.affiliation: Department of Neurosurgery, Yokohama Stroke and Brain Center, Kanagawa, Japan. Satoru4756@aol.com
authors.forename: S
authors.initials: S
authors.lastname: Shimizu
authors.forename: H
authors.initials: H
authors.lastname: Hagiwara
authors.forename: S
authors.initials: S
authors.lastname: Utsuki
authors.forename: H
authors.initials: H
authors.lastname: Oka
authors.forename: K
authors.initials: K
authors.lastname: Nakayama
authors.forename: K
authors.initials: K
authors.lastname: Fujii
mesh_terms: D003399:Craniotomy / Q000379:methods*; D006801:Humans; D008576:Meningeal Arteries / Q000033:anatomy & histology*; D019060:Minimally Invasive Surgical Procedures / Q000379:methods; D019635:Neurosurgical Procedures / Q000379:methods; D010012:Osteogenesis; D012886:Skull / Q000033:anatomy & histology*