title: Frameless stereotactic placement of foramen ovale electrodes in patients with drug-refractory temporal lobe epilepsy.
abstract: OBJECTIVE
  Semi-invasive foramen ovale electrodes (FOEs) are used as an alternative to invasive recording techniques in the presurgical evaluation of patients with temporal lobe epilepsy. To maximize patient safety and interventional success, frameless stereotactic FOE placement by use of a variation of an upper jaw fixation device with an external fiducial frame, in combination with an aiming device and standard navigation software, was evaluated by the Innsbruck Epilepsy Surgery Program.
  
  
  METHODS
  Patients were immobilized noninvasively with the Vogele-Bale-Hohner headholder (Medical Intelligence GmbH, Schwabmünchen, Germany) to plan computed tomography and surgery. Frameless stereotactic cannulation of the foramen and intracranial electrode placement were achieved with the help of an aiming device mounted to the base plate of the headholder. Ease of applicability, safety, and results obtained with foramen ovale recording were investigated.
  
  
  RESULTS
  Twenty-six FOEs were placed in 13 patients under general anesthesia. The foramen ovale was successfully cannulated in all patients. One patient reported transient painful mastication after the procedure as a complication attributable to use of the Vogele-Bale-Hohner mouthpiece. In one patient, a persistent slight buccal hypesthesia was present 3 months after the procedure. To pass the foramen, slight adjustments in the needle position had to be made in 10 sides (38.4%). To place the intracranial electrodes, adjustments were necessary six times (23.7%). An entirely new path had to be planned once (3.8%). Seizure recording provided conclusive information in all patients (100%). Outcome in operated patients was Engel Class Ia in six patients, Class IId in one patient, Class IIb in one patient, and Class IVa in one patient (minimum follow-up, 6 mo).
  
  
  CONCLUSIONS
  The Vogele-Bale-Hohner headholder combined with an external registration frame eliminates the need for invasive head clamp fixation. FOE placement can be planned "offline" and performed under general anesthesia later. This can be valuable in patients with distorted anatomy and/or small foramina or in patients not able to undergo the procedure under sedation. Results are satisfactory with regard to patient safety, patient comfort, predictability, and reproducibility. FOEs supported further treatment decisions in all patients.
authors.affiliation: Clinical Department of Neurosurgery, Innsbruck Medical University, Innsbruck, Austria. martin.ortler@i-med.ac.at
authors.forename: Martin
authors.initials: M
authors.lastname: Ortler
authors.forename: Gerlig
authors.initials: G
authors.lastname: Widmann
authors.forename: Eugen
authors.initials: E
authors.lastname: Trinka
authors.forename: Thomas
authors.initials: T
authors.lastname: Fiegele
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Eisner
authors.forename: Klaus
authors.initials: K
authors.lastname: Twerdy
authors.forename: Gerald
authors.initials: G
authors.lastname: Walser
authors.forename: Judith
authors.initials: J
authors.lastname: Dobesberger
authors.forename: Iris
authors.initials: I
authors.lastname: Unterberger
authors.forename: Reto
authors.initials: R
authors.lastname: Bale
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000627:therapeutic use; D046690:Deep Brain Stimulation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D004567:Electrodes, Implanted; D004827:Epilepsy / Q000517:prevention & control*; D005240:Feasibility Studies; D005260:Female; D054085:Foramen Ovale / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019919:Prosthesis Implantation / Q000009:adverse effects / Q000379:methods*; D013238:Stereotaxic Techniques; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D000927:Anticonvulsants