EEG Initial Ictal Discharge Frequency in Temporal Lobe Seizures Is Proportional to Degree of Hippocampal Pathology
Abstract number :
3.125
Submission category :
Year :
2000
Submission ID :
1741
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
David G Vossler, Diana L Abson Kraemer, Steven W Rostad, Bent O Kjos, Alan M Haltiner, John D Morgan, Lisa M Caylor, Robert C Knowlton, Allen R Wyler, Hisanori Hasegawa, Bradley J Davis, Swedish Neuroscience Institute, Seattle, WA; Univ of Alabama, Birmin
RATIONALE: We reported (Ann Neurol 1998;43:756-762) that the initial ictal discharge (IID) frequency in temporal lobe complex partial seizures was directly correlated with the severity of quantitative hippocampal atrophy on MRI (n=49) and the pathology grade of hippocampal sclerosis (n=22). This study was conducted in a larger group of patients to confirm the original observation, and also to determine whether the IID frequency correlates with the degree of gliosis within the lateral temporal neocortex. METHODS: Patients with EEG-video recorded complex partial seizures who underwent temporal lobectomy were prospectively included. Exclusion criteria were: EEG or clinical evidence of generalized or extratemporal epilepsy, MRI or pathology findings revealing temporal lesions other than gliosis or neuronal loss, extratemporal lesions, and previous neurosurgery. The IID frequency was measured in tenths of Hz, hippocampal volumes were calculated, and pathology was graded as we described previously. RESULTS: Between December 1992 and April 2000, 179 patients underwent temporal lobectomy. Of these, 93 met inclusion/exclusion criteria and had rhythmic waves as the IID. The median IID frequency (N=86) correlated inversely with the ipsilateral/contralateral hippocampal volume ratio (Pearson r=-.43, p<.001) and directly with the hipocampal asymmetry index (r=.39, p<.001). The median IID correlated directly with the grade of hippocampal sclerosis (n=59, r=.30, p<0.05), but not with the astrocyte count in the lateral temporal neocortex (n=60,r=.09, NS). Both MRI measures correlated with the grade of hippocampal sclerosis (n=58, r=-.56 & .47, p<0.001). The grade of hippocampal sclerosis was inversely correlated with the degree of intracortical gliosis (n=62; r=.43 p=.001). CONCLUSIONS: These findings support our original observation: faster frequency IIDs correlate with greater, and slower IIDs correlate with lesser, hippocampal pathology. Although the degree of gliosis within the lateral temporal neocortex was inversely correlated with the grade of hippocampal sclerosis, it was not correlated with the IID frequency.