title: Optimal entry point and trajectory for endoscopic third ventriculostomy: evaluation of 53 patients with volumetric imaging guidance.
abstract: OBJECTIVE
  An optimal entry point for endoscopic third ventriculostomy (ETV) helps protect critical structures from undue manipulation. A commonly accepted ideal entry point is 3 cm from the midline and 1 cm anterior to the coronal suture. The authors of this study reexamine this ideal entry point.
  
  
  METHODS
  Trajectory views from MR images or CT scans used for cranial image guidance in 53 patients (age range 3-85 years) who had undergone ETV were retrospectively evaluated. The trajectory from the tuber cinereum back through the center of the foramen of Monro was projected to the surface of the head. The relation of the entry point to the midline and the coronal suture was established.
  
  
  RESULTS
  The mean perpendicular distance from the ideal entry point to the midline was 30.1 ± 7 mm (median 31.9 mm, range 12.5-42.2 mm). The mean perpendicular distance to the coronal suture was 8.9 ± 14.1 mm posterior (median 10.4 mm), ranging from 30.6 mm anterior to 35.8 mm posterior. The entry point tended to be located more posteriorly in women and adults: 5.8 ± 15.4 mm posterior in males versus 13.1 ± 13.2 mm posterior in females (p = 0.08) and 9.1 ± 14.8 mm posterior in adults versus 8.2 ± 11.7 mm posterior in children (p = 0.84).
  
  
  CONCLUSIONS
  While the entry point may need to be modified from the ideal trajectory for other anatomical reasons, such as a trajectory through the motor cortex, in general, the authors found that the optimal entry point for ETV was more posterior than previously published and highly variable. Using image guidance or a customized trajectory based on analysis of a patient's own imaging is highly preferable to using an empirical ideal trajectory.
authors.affiliation: Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.
authors.forename: Fangxiang
authors.initials: F
authors.lastname: Chen
authors.forename: Peter
authors.initials: P
authors.lastname: Nakaji
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D003393:Cranial Sutures / Q000033:anatomy & histology / Q000601:surgery; D003627:Data Interpretation, Statistical; D004724:Endoscopy / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods*; D012727:Sex Characteristics; D025321:Surgery, Computer-Assisted / Q000379:methods*; D020542:Third Ventricle / Q000033:anatomy & histology / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D014696:Ventriculostomy / Q000379:methods*; D055815:Young Adult