N170 asymmetry as an index of inferior occipital dysfunction in patients with symptomatic occipital lobe epilepsy.
OBJECTIVE
Localizing epileptic foci in posterior brain epilepsy remains a difficult exercise in surgery for epilepsy evaluation. Neither clinical manifestations, neurological, EEG nor neuropsychological evaluations provide strong information about the area of onset, and fast spread of paroxysms often produces mixed features of occipital, temporal and parietal symptoms. We investigated the usefulness of the N170 event-related potential to map epileptic activity in these patients.


METHODS
A group of seven patients with symptomatic posterior cortex epilepsy were submitted to a high-resolution EEG (78 electrodes), with recordings of interictal spikes and face-evoked N170. Generators of spikes and N170 were localized by source analysis. Range of normal N170 asymmetry was determined in 30 healthy volunteers.


RESULTS
In 3 out of 7 patients the N170 inter-hemispheric asymmetry was outside control values. Those were the patients whose spike sources were nearest (within 3cm) to the fusiform gyrus, while foci further away did not affect the N170 ratio.


CONCLUSIONS
N170 event-related potential provides useful information about focal cortical dysfunction produced by epileptic foci located in the close neighborhood of the fusiform gyrus, but are unaffected by foci further away.


CONCLUSIONS
The N170 evoked by faces can improve the epileptic foci localization in posterior brain epilepsy.
Lopes
Ricardo
R
Department of Pediatric Neurology, Hospital Center of Central Lisbon, Rua Jacinta Marto, 1169-045 Lisbon, Portugal. r.lopes@clix.pt
Cabral
Pedro
P
Canas
Nuno
N
Breia
Paula
P
Foreid
John P
JP
Calado
Eulália
E
Silva
Rita
R
Leal
Alberto
A
D000328:Adult; D058256:Brain Waves / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009778:Occipital Lobe / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011930:Reaction Time / Q000502:physiology; D013702:Temporal Lobe / Q000503:physiopathology; D055815:Young Adult