Usefulness of the dipole tracing method with a scalp-skull-brain head model: relationship between the epileptic focus and equivalent current dipole locations.
OBJECTIVE
We examined whether the dipole tracing (DT) method with a realistic three-shell head model and inhomogeneous electric conductivity is useful to estimate the epileptic focus from interictal spikes.


METHODS
This study included 17 temporal lobe epilepsy (TLE) cases, classified into three types as type A (unilateral), type B (intermediate) and type C (bilateral) and 5 extratemporal epilepsy (XTLE) cases. The epileptic areas were determined by noninvasive and/or invasive examinations. Selected interictal spikes were analyzed and the calculated equivalent current dipoles (ECDs) of dipolarity greater than 0.98 were superimposed over the realistic head model in each patient. We evaluated the ECD concentration within and around the epileptic area.


RESULTS
In TLE cases, types A showed better ECD concentration (87%) within the epileptic area than other types (type B: 68%; type C: 74%). XTLE exhibited variable ECD distribution within and around the epileptic area.


CONCLUSIONS
The DT method with a realistic head model and inhomogeneous electric conductivity can be useful to estimate the epileptic area from interictal spikes, especially in unilateral TLE cases.
Chitoku
S
S
Department of Neurosurgery, Nara Medical University, Japan. chitoku@nmu-gw.naramed-u.ac.jp
Hoshida
T
T
Hirabayashi
H
H
Sakaki
T
T
D000200:Action Potentials; D001931:Brain Mapping / Q000379:methods*; D004553:Electric Conductivity; D004827:Epilepsy / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology; D006801:Humans; D008954:Models, Biological; D013238:Stereotaxic Techniques