First true initial ictal SPECT in partial epilepsy verified by electroencephalography

Jesús Pastor¹, Luis Domínguez-Gadea², Rafael G Sola³, Virgilio Hernando³, María Luisa Meilán⁴, Eva De Dios⁴, José Luis Martínez-Chacón⁴, Marcos Martínez⁵

¹Clinical Neurophysiology; ²Nuclear Medicine; ³Neurosurgery; ⁴Anaesthesiology and Reanimation; Hospital Universitario “La Princesa”, Madrid, Spain; ⁵Anaesthesiology and Reanimation, Cardiovascular Unit of Adults, Hospital Ramón y Cajal, Madrid, Spain

Abstract: Drug-resistant epilepsy can sometimes be treated by surgery. In these cases, an accurate identification of the epileptogenic area must be addressed before resection. Ictal SPECT is one of the presurgical evaluations that can be performed, but usually, the increase in the regional cerebral perfusion observed is produced by diffusion of ictal activity. Here we describe a patient studied with v-EEG and foramen ovale electrodes that suffered a seizure after intravenous infusion of etomidate. The sequence of etomidate administration, followed by radiotracer and seizure was good enough for us to suspect that a true initial ictal SPECT was observed. We have implemented a kinetic model with four compartments, previously described (Andersen 1989), in order to estimate the fraction of hydrophilic radiotracer in the brain during the pre-ictal and ictal periods. This model has shown that the fraction of hydrophilic radiotracer during the seizure into the brain would be between 18.9% and 42.3% of total infused. We show the first true initial ictal SPECT demonstrated by bioelectrical recordings of the brain activity, obtained by a correct succession of events and compatible with theoretical data obtained from the kinetic model.

Keywords: etomidate, foramen ovale electrodes, mathematical model, temporal lobe epilepsy