Abstracts

Rationale: The delineation of the epileptogenic zone in patients with non-lesional extratemporal lobe epilepsies (ETLE) it the major challenge in epileptology. The aim of the present study was to investigate the utility of ictal single photon emission computed tomography (SPECT) without subtraction and magnetic resonance imaging (MRI) co-registration in decision making for epilepsy surgery in patients with non-lesional ETLE.Methods: The patients with suspected non-lesional ETLE (non-localizing or discordant non-invasive data during the prolonged Video-EEG-Monitoring and negative MRI) were subjected to ictal SPECT studies for planning invasive monitoring or surgery strategy. Ictal SPECT was considered to be useful for decision-making if it obviated the need for invasive monitoring or influenced its planning ictal SPECT.Results: 36 patients with suspected non-lesional ETLE (mean age 32,68 9,6 years) underwent SPECT studies between January 2000 and May 2011. 9 patients were excluded from further analyses due to missing data or unsuccessful ictal SPECT. Thus the ictal SPECT of 25 patients were investigated. The time from clinical onset of seizure and injection was from 6 to 38 sec (mean 13,28 9,07 sec). The patients were divided into two groups: those where the non-invasive evaluation presumed a seizure onset zone in one region (localizable), and those where the seizure onset zone was not lateralizable or localizable (non-localizable). Ictal SPECT was decided to be successful if it provided any additional information for localization of epileptogenic zone. In 6 of 14 patients (43%) of localizable group ictal SPECT provided additional information, whereas only in 1 of 11 patients (9%) of non-localizable group ictal SPECT was helpfull in decision-making and planning the invasive recordings (p=0,07).Conclusions: : Ictal SPECT provided more localizing information and influenced the final decision-making only in patients were based on the non-invasive monitoring results the seizure onset zone could be localized to one region of the brain. Ictal SPECT is useful in a selected group of patients and unlikely to provide additional information in others. These findings need to be validated in a larger group of patients. The subtraction with interictal SPECT would also improve these results.