Origin of frontal lobe spikes in the early onset benign occipital lobe epilepsy (Panayiotopoulos syndrome)

Abstract

Objective: Early onset benign occipital lobe epilepsy (Panayiotopoulos syndrome [PS]) is a common and easily recognizable epilepsy. Interictal EEG spike activity is often multifocal but most frequently localized in the occipital lobes. The origin and clinical significance of the extra-occipital spikes remain poorly understood. Methods: Three patients with the PS and interictal EEG spikes with frontal lobe topography were studied using high-resolution EEG. Independent component analysis (ICA) was used to decompose the spikes in components with distinct temporal dynamics. The components were mapped in the scalp with a spline-laplacian algorithm. Results: The change in scalp potential topography from spike onset to peak, suggests the contribution of several intracranial generators, with different kinetics of activation and significant overlap. ICA was able to separate the major contributors to frontal spikes and consistently revealed an early activating group of components over the occipital areas in all the patients. The local origin of these early potentials was established by the spline-laplacian montage. Conclusions: Frontal spikes in PS are consistently associated with early and unilateral occipital lobe activation, suggesting a posteroanterior spike propagation. Significance: Frontal spikes in the PS represent a secondary activation triggered by occipital interictal discharges and do not represent an independent focus.

N170 asymmetry as an index of inferior occipital dysfunction in patients with symptomatic occipital lobe epilepsy

“…This fast spread dynamics makes it difficult to localize the epileptogenic cortex not only in the raw EEG traces (Leal et al, 2008), but also using source analysis methods (Van der Meij et al, 1997). Several issues may be responsible for the poor yield of the latte techniques but the reduced spatial sampling over the posterior and inferior scalp, usually used in clinical studies, seems to be a prominent one (Leal et al, 2008).…”

“…This fast spread dynamics makes it difficult to localize the epileptogenic cortex not only in the raw EEG traces (Leal et al, 2008), but also using source analysis methods (Van der Meij et al, 1997). Several issues may be responsible for the poor yield of the latte techniques but the reduced spatial sampling over the posterior and inferior scalp, usually used in clinical studies, seems to be a prominent one (Leal et al, 2008). Careful studies comparing the localization of sources obtained by solving the inverse problem and well-known occipital foci are lacking in the literature, but would represent a major contribution to establish the contribution of source analysis in this clinical setting.…”

“…Epileptic activity in occipital lobe epilepsies tends to propagate to nearby parietal, temporal and also to the distant frontal lobes (Leal et al, 2007(Leal et al, , 2008Williamson et al, 1992). Such phenomenon is responsible for the complex ictal manifestations involving diverse brain areas, making it difficult to obtain a clear picture of the overall dynamics and potentially leading to important errors when surgery for epilepsy is considered.…”

“…The visual analysis of the EEG in occipital lobe epilepsies is poorly localized (Williamson et al, 1992) and the complex dynamics of spike activity requires the use of sophisticated methods of data analysis (Leal et al, 2007(Leal et al, , 2008, which have not been used very often in the surgery for epilepsy setting.…”

Neuropsychological abnormalities in children with the Panayiotopoulos syndrome point to parietal lobe dysfunction

“…As in other benign childhood epilepsies, there is no significant cognitive impairment relevant to daily activities, and the neurological status is normal between seizure events. Because the EEG scalp paroxysms are complex and variable between patients [3], no consistent clues to the localization of the epileptogenic area are obtainable besides the general idea that the posterior cortex is mainly involved [4,5].…”