title: The effects of anatomic variations on stereotactic laser amygdalohippocampectomy and a proposed protocol for trajectory planning.
abstract: BACKGROUND
  Stereotactic laser amygdalohippocampectomy (SLAH) is a promising minimally invasive alternative for mesial temporal lobe epilepsy. As seizure outcome has been associated with the extent of amygdalar and hippocampal ablation, it is important to select a safe trajectory optimizing involvement of both structures; however, variations in temporal anatomy significantly affect the overall complexity of planning.
  
  
  OBJECTIVE
  To quantify anatomic variables of SLAH and facilitate stereotactic planning by developing a protocol for optimally targeting the amygdalohippocampal complex (AHC).
  
  
  METHODS
  We performed a retrospective analysis of 19 SLAHs. Anatomic measurements from preoperative magnetic resonance imaging and laser trajectory measurements from coregistered postoperative magnetic resonance imaging were taken in 11 patients. Simple linear regression analysis was performed to identify significant predictor variables determining ablation extent. Based on these data, a protocol for optimal trajectory planning was developed and subsequently implemented in 8 patients.
  
  
  RESULTS
  The medial angle of the laser trajectory correlated with the medial angle of the AHC. The length of amygdalar cannulation was predictive of its ablation volume. All trajectories passed through a posteroinferior corridor formed by the lateral ventricle superiorly and collateral sulcus inferiorly. Our protocol facilitated planning and increased the volume of AHC ablation.
  
  
  CONCLUSIONS
  The medial AHC angle dictates the medial trajectory angle and a path from the posteroinferior corridor through the hippocampus and the center of the amygdala dictates the caudal angle. These observations led to a protocol for long-axis AHC cannulation that maintains an extraventricular trajectory to minimize hemorrhage risk and targets the center of the amygdala to optimize ablation volumes.
authors: Departments of *Neurosurgery and ‡Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania.
authors: Chengyuan
authors: C
authors: Wu
authors: David W
authors: DW
authors: Boorman
authors: Richard J
authors: RJ
authors: Gorniak
authors: Christopher J
authors: CJ
authors: Farrell
authors: James J
authors: JJ
authors: Evans
authors: Ashwini D
authors: AD
authors: Sharan
mesh_terms: D000328:Adult; D000368:Aged; D000679:Amygdala / Q000033:anatomy & histology / Q000601:surgery*; D063405:Anatomic Variation; D017115:Catheter Ablation / Q000379:methods*; D002648:Child; D004833:Epilepsy, Temporal Lobe / Q000601:surgery*; D005260:Female; D006624:Hippocampus / Q000033:anatomy & histology / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D053685:Laser Therapy / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009493:Neurosurgery; D012189:Retrospective Studies; D055815:Young Adult