Foramen ovale electrodes can identify a focal seizure onset when surface EEG fails in mesial temporal lobe epilepsy.
OBJECTIVE
We analyze a series of patients with mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) submitted to presurgical investigation with scalp sphenoidal, followed by foramen ovale electrodes (FO), and, when necessary, with depth temporal electrodes. We sought to evaluate the clinical utility of FO in patients with MTLE-HS.


METHODS
We included patients who had phase I investigation with bitemporal independent seizures, nonlateralized ictal onsets, or ictal onset initiating in the side contralateral to the side of hippocampal sclerosis. Patients whose implanted FO failed to demonstrate an unambiguous unilateral ictal onset were later evaluated with depth hippocampal electrodes.


RESULTS
Between May 1994 and December 2004, 64 patients met our inclusion criteria: 33 female (51.5%) and 31 male subjects (48.5%). The mean age at enrollment was 37.66+/-10.6 years (range, 12-56 years). The groups with nonlateralized surface ictal EEG onsets and contralateral EEG onsets had a greater chance of lateralization with FO when compared with the group with bilateral independent seizures on surface EEG (p<0.01). Foramen ovale electrodes lateralized the seizures in 60% of patients. Seventy percent of patients became seizure free after temporal lobectomy. Five patients were implanted with depth temporal electrodes after FO video-EEG monitoring. The depth-electrode EEG onsets confirmed the results of FO video-EEG monitoring in all patients, and the surgery was refused.


CONCLUSIONS
In MTLE-HS, FO is a reliable method for lateralization of seizures that are not clearly recorded by surface EEGs.
Velasco
Tonicarlo R
TR
CIREP, Centro de Cirurgia de Epilepsia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil. tvelasco@rnp.fmrp.usp.br
Sakamoto
Américo C
AC
Alexandre
Veriano
V
Walz
Roger
R
Dalmagro
Charles L
CL
Bianchin
Marino M
MM
Araújo
David
D
Santos
Antônio C
AC
Leite
João P
JP
Assirati
João A
JA
Carlotti
Carlos
C
D000293:Adolescent; D000328:Adult; D038481:Anterior Temporal Lobectomy; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods* / Q000706:statistics & numerical data; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006346:Heart Septum; D006624:Hippocampus / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011300:Preoperative Care; D013702:Temporal Lobe / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome; D014743:Videotape Recording