title: Optic radiation tractography and vision in anterior temporal lobe resection.
abstract: OBJECTIVE
  Anterior temporal lobe resection (ATLR) is an effective treatment for refractory temporal lobe epilepsy but may result in a contralateral superior visual field deficit (VFD) that precludes driving in the seizure-free patient. Diffusion tensor imaging (DTI) tractography can delineate the optic radiation preoperatively and stratify risk. It would be advantageous to incorporate display of tracts into interventional magnetic resonance imaging (MRI) to guide surgery.
  
  
  METHODS
  We studied 20 patients undergoing ATLR. Structural MRI scans, DTI, and visual fields were acquired before and 3 to 12 months following surgery. Tractography of the optic radiation was performed on preoperative images and propagated onto postoperative images. The anteroposterior extent of the damage to Meyer's loop was determined, and visual loss was quantified using Goldmann perimetry.
  
  
  RESULTS
  Twelve patients (60%) suffered a VFD (10-92% of upper quadrant; median, 39%). Image registration took <3 minutes and predicted that Meyer's loop was 4.4 to 18.7mm anterior to the resection margin in these patients, but 0.0 to 17.6mm behind the resection margin in the 8 patients without VFD. The extent of damage to Meyer's loop significantly correlated with the degree of VFD and explained 65% of the variance in this measure.
  
  
  CONCLUSIONS
  The optic radiation can be accurately delineated by tractography and propagated onto postoperative images. The technique is fast enough to propagate accurate preoperative tractography onto intraoperative scans acquired during neurosurgery, with the potential to reduce the risk of VFD.
authors.affiliation: Epilepsy Society Magnetic Resonance Imaging Unit, Department of Clinical and Experimental Epilepsy, University College London Institute of Neurology, and Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London, United Kingdom. g.winston@ucl.ac.uk
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Winston
authors.forename: Pankaj
authors.initials: P
authors.lastname: Daga
authors.forename: Jason
authors.initials: J
authors.lastname: Stretton
authors.forename: Marc
authors.initials: M
authors.lastname: Modat
authors.forename: Mark R
authors.initials: MR
authors.lastname: Symms
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McEvoy
authors.forename: Sebastien
authors.initials: S
authors.lastname: Ourselin
authors.forename: John S
authors.initials: JS
authors.lastname: Duncan
mesh_terms: D000293:Adolescent; D000328:Adult; D056324:Diffusion Tensor Imaging / Q000379:methods*; D004833:Epilepsy, Temporal Lobe / Q000378:metabolism / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D011300:Preoperative Care / Q000379:methods*; D013702:Temporal Lobe / Q000378:metabolism / Q000601:surgery*; D014786:Vision Disorders / Q000209:etiology / Q000517:prevention & control; D014785:Vision, Ocular / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*; D014795:Visual Pathways / Q000378:metabolism; D055815:Young Adult