title: Brain retraction and thickness of cerebral neocortex: an automated technique for detecting retraction-induced anatomic changes using magnetic resonance imaging.
abstract: BACKGROUND
  Treating deep-seated cerebral lesions often requires retracting the brain. Retraction, however, causes clinically significant postoperative neurological deficits in 3% to 9% of intracranial cases.
  
  
  OBJECTIVE
  This pilot study used automated analysis of postoperative magnetic resonance images (MRIs) to determine whether brain retraction caused local anatomic changes to the cerebral neocortex and whether such changes represented sensitive markers for detecting brain retraction injury.
  
  
  METHODS
  Pre- and postoperative maps of whole-brain cortical thickness were generated from 3-dimensional MRIs of 6 patients who underwent selective amygdalohippocampectomy for temporal lobe epilepsy (5 left hemispheres, 1 right hemisphere). Mean cortical thickness was determined in the inferior temporal gyrus (ITG test), where a retractor was placed during surgery, and in 2 control gyri-the posterior portion of the inferior temporal gyrus (ITG control) and motor cortex control. Regions of cortical thinning were also compared with signs of retraction injury on early postoperative MRIs.
  
  
  RESULTS
  Postoperative maps of cortical thickness showed thinning in the inferior temporal gyrus where the retractor was placed in 5 patients. Postoperatively, mean cortical thickness declined from 4.1 +/- 0.4 mm to 2.9 +/- 0.9 mm in ITG test (P = .03) and was unchanged in the control regions. Anatomically, the region of neocortical thinning correlated with postoperative edema on MRIs obtained within 48 hours of surgery.
  
  
  CONCLUSIONS
  Postoperative MRIs can be successfully interrogated for information on cortical thickness. Brain retraction is associated with chronic local thinning of the neocortex. This automated technique may be sensitive enough to detect regions at risk for functional impairment during craniotomy that cannot be easily detected on postoperative structural imaging.
authors.affiliation: Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Little
authors.forename: Seban
authors.initials: S
authors.lastname: Liu
authors.forename: Scott
authors.initials: S
authors.lastname: Beeman
authors.forename: Tejas
authors.initials: T
authors.lastname: Sankar
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
authors.forename: Leland S
authors.initials: LS
authors.lastname: Hu
authors.forename: Kris A
authors.initials: KA
authors.lastname: Smith
authors.forename: Leslie C
authors.initials: LC
authors.lastname: Baxter
mesh_terms: D000328:Adult; D000679:Amygdala / Q000601:surgery; D001931:Brain Mapping; D015331:Cohort Studies; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000601:surgery; D005260:Female; D007839:Functional Laterality; D006624:Hippocampus / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000473:pathology*; D019635:Neurosurgical Procedures; D010865:Pilot Projects; D011184:Postoperative Period; D012189:Retrospective Studies; D013997:Time Factors; D055815:Young Adult