Early Contralateral Neocortical Activation Might Explain False or Non-Localizatory Surface Video-EEG Findings.
Abstract number :
2.175
Submission category :
Year :
2000
Submission ID :
2770
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
Elcio Machado, Jose A Buratini, Meire Argentoni, Viviane B Ferreira, Arthur Cukiert, Cassio Forster, Leila Frayman, Alcione Sousa, Joaquim Vieira, Hosp Brigadeiro, Sao Paulo Sp, Brazil; Hosp Brigadeiro, Sao Paulo Sp, Brazil.
RATIONALE: This paper discusses the results obtained in patients with refractory bitemporal epilepsy (BiTE) submitted to invasive recordings in whom the surface and depth neurophysiological findings were discordant. METHODS: Three adult patients with refractory BiTE who were submitted to bilateral subdural implantation were studied. Patients were implanted with a 32-contacts grid over each temporal lobe. RESULTS: Patient I had simple (SPS)autonomic and complex partial seizures (CPS). He had interictal bilateral independent temporal lobe spiking (BITLS) (left=right). Ictal recordings were not localizatory. MRI showed bilateral mesial temporal sclerosis (MTS). During invasive monitoring (IM), seizure onset occurred at the RIGHT parahippocampal contacts. Afterwards, spreading to the LEFT parahippocampal gyrus and neocortex was noted, while no ictal activity was being recorded from the RIGHT temporal neocortex. He was submitted to a right cortico-amigdalo-hippocampectomy (CAH). Patient II had SPS and CPS. Interictal surface EEG showed BITLS with a clear RIGHT side predominance (>90%). Ictal video-EEG suggested a left temporal lobe onset. MRI showed a right temporo-polar arachnoid cyst. During IM, all seizures arised from the LEFT side. Interictal activity continue to prevail (>90%)at the right temporal lobe. He was submitted to a left CAH. Patient III had CPS. Interictal EEG showed BITLS (left=right). MRI was normal. Ictal recordings were non-localizatory. During IM seizures started with desynchronization of the background activity over the LEFT temporal lobe and a recruiting pattern over the left superior temporal gyrus. Ictal activity spread to the RIGHT temporal lobe while no ictal activity was being recorded from the left temporal lobe. Ictal semiology suggested a left ictal onset even when no ictal activity was being recorded over the left temporal lobe. He was submitted to a left CAH. CONCLUSIONS: These 3 patients represent samples of how surface EEG results could be misleading. Patients with bitemporal epilepsy and normal MRI or imaging findings of bilateral MTS or lesions should be investigated with IM preoperatively.