Abstract
Simultaneous EEG–fMRI offers the possibility of non-invasively studying the spatiotemporal dynamics of epileptic activity propagation from the focus towards an extended brain network, through the identification of the haemodynamic correlates of ictal electrical discharges. In epilepsy associated with hypothalamic hamartomas (HH), seizures are known to originate in the HH but different propagation pathways have been proposed. Here, Dynamic Causal Modelling (DCM) was employed to estimate the seizure propagation pathway from fMRI data recorded in a HH patient, by testing a set of clinically plausible network connectivity models of discharge propagation. The model consistent with early propagation from the HH to the temporal–occipital lobe followed by the frontal lobe was selected as the most likely model to explain the data. Our results demonstrate the applicability of DCM to investigate patient-specific effective connectivity in epileptic networks identified with EEG–fMRI. In this way, it is possible to study the propagation pathway of seizure activity, which has potentially great impact in the decision of the surgical approach for epilepsy treatment.
Highlights
Hypothalamic hamartomas (HH) are benign brain tumours located near the hypothalamus
The statistical parametric maps (SPMs) of seizure-related BOLD signal positive changes obtained with the conventional General Linear Model (GLM) analysis is first presented, followed by the results obtained by the Dynamic Causal Modelling (DCM) and Lagged GLM analyses
Significant BOLD increases were observed in the HH, precuneus, posterior division of cingulate gyrus, left hippocampus and contiguous left occipital lobe, and left frontal lobe
Summary
Epileptic patients with HHs often experience gelastic or dacrystic seizures, which typically involve sudden bursts of energy in the form of laughing or weeping, not accompanied by the usual emotional sense of amusement or sadness, respectively (Berkovic et al, 1988). The complete control of seizures and improvement on behavioural disturbances can be achieved by resecting the HH, which is a reasonable choice compared to the relatively severe evolution of medically-treated HH associated epilepsy (Berkovic et al, 1988; Tassinari et al, 1997). In an unsuccessful HH resection, the interruption of seizure propagation through disconnection of the underlying pathways is an alternative surgical approach (Fohlen et al, 2003). The exact pathway is not known in general and it must be investigated in each patient
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