Localizing value of scalp EEG spikes: a simultaneous scalp and intracranial study.
OBJECTIVE
To determine the relationship between cortical origins of interictal and ictal EEG discharges in patients with temporal lobe epilepsy.


METHODS
Simultaneous cortical and scalp EEG recordings were obtained from six patients with temporal lobe epilepsy. Subdural electrode contacts active at seizure onset and when scalp ictal rhythms became evident were identified. Similarly, cortical substrates of scalp EEG spikes were identified at spike peak and at the initial rising phase of the potential.


RESULTS
Intracranial seizure onsets were commonly focal and involved only a few electrode contacts, as opposed to scalp ictal rhythms, which required synchronous activation of multiple electrode contacts. At the peak of scalp spikes, multiple electrode contacts were similarly active. However, at spike onset, cortical substrates were more discrete and commonly involved electrodes similar to that of seizure onsets.


CONCLUSIONS
Scalp EEG ictal rhythms and the peak of a scalp spike may poorly localize the epileptogenic focus because of propagation. Cortical source area at scalp spike onset is more discrete, however, and the seizure onset zone often lies within this area.


CONCLUSIONS
Analysis of scalp spikes, such as source modeling, at their initial rising phase might provide useful localizing information about seizure origins in the same patient.
Ray
Amit
A
Department of Neurology, Section of Epilepsy, Cleveland Clinic Foundation, Cleveland, OH, USA. rayamit@gmail.com
Tao
James X
JX
Hawes-Ebersole
Susan M
SM
Ebersole
John S
JS
D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D004566:Electrodes; D004569:Electroencephalography; D006801:Humans; D012535:Scalp / Q000503:physiopathology*; D012640:Seizures / Q000503:physiopathology*