title: Foramen ovale electrodes can identify a focal seizure onset when surface EEG fails in mesial temporal lobe epilepsy.
abstract: 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.
authors.affiliation: CIREP, Centro de Cirurgia de Epilepsia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil. tvelasco@rnp.fmrp.usp.br
authors.forename: Tonicarlo R
authors.initials: TR
authors.lastname: Velasco
authors.forename: Américo C
authors.initials: AC
authors.lastname: Sakamoto
authors.forename: Veriano
authors.initials: V
authors.lastname: Alexandre
authors.forename: Roger
authors.initials: R
authors.lastname: Walz
authors.forename: Charles L
authors.initials: CL
authors.lastname: Dalmagro
authors.forename: Marino M
authors.initials: MM
authors.lastname: Bianchin
authors.forename: David
authors.initials: D
authors.lastname: Araújo
authors.forename: Antônio C
authors.initials: AC
authors.lastname: Santos
authors.forename: João P
authors.initials: JP
authors.lastname: Leite
authors.forename: João A
authors.initials: JA
authors.lastname: Assirati
authors.forename: Carlos
authors.initials: C
authors.lastname: Carlotti
mesh_terms: 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