Frameless Stereotactic Placement of a Minimally Invasive Depth Electrode for EEG Investigation of Mesiotemporal Structures.
Abstract number :
3.203
Submission category :
Year :
2001
Submission ID :
302
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
C.R. Mascott, M.D., Tulane Epilepsy Insitiute, Tulane University, New Orleans, LA; T. Frederick, M.D., Tulane Epilepsy Institute, Tulane University, New Orleans, LA
RATIONALE: Intracranial electrodes are implanted in candidates for resective epilepsy surgery when localization of seizure onset patterns is difficult to determine by non-invasive means. Indications for these include non-localizing scalp EEG or incongruence between EEG and imaging or amobarbital testing. Electrodes can be stereotactically implanted or placed subdurally. There is evidence that stereotactically placed electrodes may be somewhat superior for the investigation of mesiotemporal structures. The most common strategies for stereotactic placement of depth electrodes include orthogonal placement of multiple electrodes per side or placement of a single electrode per side transfixing the hippocampus and amygdala. Risks include infection and hemorrhage.
METHODS: We describe a method of posterior placement of a single electrode covering amygdala and hippocampus. Contrary to the usual posterior approach, the electrode is placed in the temporal horn of the lateral ventricle, thus avoiding direct injury to mesiotemporal structures. For consistently accurate placement, we employed frameless stereotactic planning using image-fused CT and MRI models of the ventricles (ImMerge TM, StealthStation TM, Sofamor Danek, Memphis TN). So far a total of 12 ventricular electrodes in 6 patients have been placed. In addition, all patients had orthogonally placed electrodes in bilateral amygdalae and hippocampae as well as bilateral subtemporal strips (Ad-Tech, Racine, Wisconsin).
RESULTS: Accurate placement was obtained of all temporal horn electrodes as confirmed by post-implantation MRI. Mesiotemporal EEG seizure onsets in the ventricular electrode contacts were comparable to those recorded in orthogonally implanted depth electrodes and superior to recordings from subtemporal strips.
CONCLUSIONS: We have described a method for consistently accurate placement of temporal horn electrodes for investigation of epilepsy. Preliminary data indicate that these electrodes may have the EEG sensitivity of electrodes transfixing mesiotemporal structures with considerably less risk of bitemporal injury. For this reason we view these electrodes as minimally invasive.