Brain Mapping of Epileptic Activity in a Case of Idiopathic Occipital Lobe Epilepsy (Panayiotopoulos Syndrome)

Abstract

Summary:The Panayiotopoulos type of occipital lobe epilepsy has generated great interest, but the particular brain areas involved in the peculiar seizure manifestations have not been established. We studied a patient with the syndrome, using highresolution EEG and simultaneous EEG and functional magnetic resonance imaging (fMRI). Resolution of the scalp EEG was improved using a realistic spline Laplacian algorithm, and produced a complex distribution of current sinks and sources over the occipital lobe. The spike-related blood oxygen level dependent (BOLD) effect was multifocal, with clusters in lateral and inferior occipital lobe and lateral and anterior temporal lobe. We also performed regional dipole seeding in BOLD clusters to determine their relative contribution to generation of scalp spikes. The integrated model of the neurophysiologic and vascular data strongly suggests that the epileptic activity originates in the lateral occipital area, spreading to the occipital pole and lateral temporal lobe. Key Words: Epilepsy-Occipital lobe-BOLD-Childhood.The most common syndrome of idiopathic occipital lobe epilepsy (IOLE) has been a source of puzzling questions since its description by Panayiotopoulos (Panayiotopoulos, 1989). The cardinal ictal manifestations of vomiting, eye deviation and long periods of interruption of consciousness, with rare visual symptoms, constitutes an unusual constellation of symptoms and up to now very little is known about the particular cortical structures involved in their generation. The consistent clinical picture in affected children suggests that a common epileptic network is at work and persists with little change throughout the evolution of the syndrome. The variability of the EEG (Panayiotopoulos, 2002) CASE REPORTA healthy 11-year-old boy, with no previous history of seizures, was found with the eyes turned to one side, not responding to verbal stimulation and a pale face, while resting in the beach. He recovered normal behavior after a few minutes. Hours later, while resting in a sofa, he repeated the symptoms, which also lasted for a few minutes. Medical evaluation at an emergency department half an hour later failed to find any abnormality and he was discharged with an EEG booked for the next day.The EEG revealed almost continuous spike activity over the left posterior areas, and he was admitted to the Intensive Care Unit for vigilance, despite the fact that he remained alert and with a normal neurological status. No evidence supporting persisting clinical seizures was found.An ambulatory device using the full 10-20 system was used to monitor continuously the EEG (24 h). The prominent left posterior spike activity with the eyes closed was confirmed, as well as its striking decrease while recording with the eyes open, which led to he diagnosis of IOLE. The patient was medicated with sodium valproate and remains seizure-free after 6 months. 1179

The value of EEG‐fMRI and EEG source analysis in the presurgical setup of children with refractory focal epilepsy

“…First, the localization of hemodynamic changes related to IED is not very specific, and thus leads to BOLD signals being classified as diffuse and discordant. In most of the EEG‐fMRI studies, significant IED correlated BOLD changes were not exclusively observed in the presumed epileptogenic zone but in several additional brain areas demonstrating an extended network underlying IED (Boor et al., 2003; Leal et al., 2006; Boor et al., 2007; De Tiege et al., 2007; Jacobs et al., 2007a; Leal et al, 2007; Lengler et al., 2007; Groening et al., 2009). This may result from setting the threshold too low, revealing activated brain areas that appear simply by chance (Lengler et al., 2007; Zijlmans et al., 2007).…”

Signal change in hippocampus and current source of spikes in Panayiotopoulos syndrome

“…In recent studies, using current source analysis of EEG, simultaneous EEG/functional MRI, and magnetoencephalography, it was found that the epileptic activity of PS originates in the lateral occipital cortex and rapidly spreads to the cortical areas of the temporal or parietal lobes10,11) or the temporocentrofrontal cortex12). In another study that reviewed ictal EEGs revealed that there was no specific focus related to the autonomic symptoms.…”

“…The temporal area may also be included in the network. The studies about interictal and ictal discharges of PS suggest that the temporal lobe may be one of the hyperexcitable or irritative areas and part of the epileptogenic area in PS patients 11-13).…”

SimultaneousEEGand fMRIrecordings (EEG‐fMRI) in children with epilepsy

“…In other idiopathic focal epilepsies (benign occipital lobe epilepsies of a Gastaut type and Panayiotopoulos type), Leal et al. (, ) found an activation pattern in different cortical occipital and parietal areas that corresponded well with the localization of IED. The authors suggested that EEG‐fMRI provides a more satisfactory mapping of the irritative zone than that obtained from EEG source analysis.…”