title: Frameless stereotactic cannulation of the foramen ovale for ablative treatment of trigeminal neuralgia.
abstract: OBJECTIVE
  Ablative neurosurgical treatment of trigeminal neuralgia, including percutaneous radiofrequency thermocoagulation, requires cannulation of the foramen ovale. To maximize patient security and cannulation success, a frameless stereotactic system was evaluated in a phantom study, a cadaveric study, and a preliminary clinical trial.
  
  
  METHODS
  Frameless stereotaxy using an optical navigation system, an aiming device, and a noninvasive vacuum mouthpiece-based registration and patient fixation technique was used for the targeting of a test body based on 1-, 3-, and 5-mm axial computed tomographic slices and of the foramen ovale in three cadavers and 15 patients based on 3-mm axial computed tomographic slices.
  
  
  RESULTS
  The mean normal (x/y) localization accuracy/standard deviation (n = 360) was 1.31/0.67 mm (1-mm slices), 1.38/0.65 mm (3-mm slices), and 1.84/0.96 mm (5-mm slices). Significantly better results were achieved with 1- and 3-mm slices when compared with 5-mm slices (P < 0.001). The foramen ovale (3 x 6 mm) was successfully cannulated at the first attempt in all cadavers and patients, which indicates clinical localization accuracies better than 1.5 mm in the anteroposterior and 3 mm in the medial-lateral directions.
  
  
  CONCLUSIONS
  Based on the noninvasive Vogele-Bale-Hohner vacuum mouthpiece, there is no need for invasive head clamp fixation. Imaging, real laboratory simulation, and the actual surgical intervention can be separated in time and location. The presented data suggest that frameless stereotaxy is a predictable and reproducible procedure, which may enhance patient security and cannulation success independent of the surgeon's experience.
authors.affiliation: Department of Radiology, Medical University Innsbruck, Innsbruck, Austria. reto.bale@uibk.ac.at
authors.forename: Reto J
authors.initials: RJ
authors.lastname: Bale
authors.forename: Ilse
authors.initials: I
authors.lastname: Laimer
authors.forename: Arno
authors.initials: A
authors.lastname: Martin
authors.forename: Andreas
authors.initials: A
authors.lastname: Schlager
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayr
authors.forename: Michael
authors.initials: M
authors.lastname: Rieger
authors.forename: Benedikt V
authors.initials: BV
authors.lastname: Czermak
authors.forename: Peter
authors.initials: P
authors.lastname: Kovacs
authors.forename: Gerlig
authors.initials: G
authors.lastname: Widmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D017115:Catheter Ablation / Q000295:instrumentation / Q000379:methods*; D002404:Catheterization / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006346:Heart Septum / Q000473:pathology* / Q000601:surgery; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D013238:Stereotaxic Techniques; D025321:Surgery, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D016896:Treatment Outcome; D014277:Trigeminal Neuralgia / Q000473:pathology / Q000601:surgery*