Memory complaints, memory disorders and focus localization in patients with partial epilepsy

Our study aimed at analysing effects of epileptic foci on memory function in patients with partial epilepsy. Twenty-eight patients with spontaneous memory complaints and psychometrically established memory disorders were assessed by 21-channel electroencephalography recorded both during cognitive testing and during 99mTc-HMPAO single photon emission computed tomography (SPECT). Computed tomography (CT) was performed on the same day. None of the epilepsy-related factors (seizure type, seizure frequency, type of epilepsy, age at onset of the seizures, type of antiepileptic treatment) could be related directly to severity or type of memory impairment (classified into the categories 'global', 'verbal' and 'non-verbal'). Remarkably, this study found no significant relationship between EEG focus localization and severity of measured memory impairment. Most areas with hypoperfusion on the SPECT were found in the group with global (severe) amnesia, typically with a right frontal localization. Abnormalities on CT were predominantly found in the same group, however, with a right-sided parietal localization. An unanticipated finding was that the majority of temporal CT and SPECT lesions were found in the group with relatively better memory performance.