Quantitative Comparison of Cell Loss and Thiopental‐Induced EEG Changes in Human Epileptic Hippocampus

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Abstract
Thiopental-induced EEG .beta. activity recorded from mesial and lateral temporal lobe sites was analyzed both visually and by computer in 30 patients with complex partial seizures. All patients later received anterior temporal lobectomy. Volumetric cell densites and percentage of principal cell loss relative to normal controls were determined in several different areas of each resected temporal lobe. The percentage of drug-induced .beta. activity was then compared with the percentage of cell loss by (a) making precise topographic correlations between induced .beta. and cell loss, (b) relating the overall degree of left/right .beta. asymmetry to cell loss averaged over wide regions, and (c) comparing the likelihood of left/right .beta. asymmetries in patients with and without extreme cell loss. The results obtained were consistently negative and were unaffected by whether EEG data were analyzed by computer or visual inspection. These results indicate that the well-known loss of drug-induced .beta. activity found in epileptogenic regions is not an indicator of the degree of cell loss of sclerosis. The underlying focal dysfunction measured by EEG .beta. activity remains unknown, and factors such as focal hypoperfusion, hypometabolism, and the microanatomic features of the cells remaining in the focus should be investigated.