Widespread grey matter changes and hemodynamic correlates to interictal epileptiform discharges in pharmacoresistant mesial temporal epilepsy

Abstract

Focal onset epilepsies most often occur in the temporal lobes. To improve diagnosis and therapy of patients suffering from pharmacoresistant temporal lobe epilepsy it is highly important to better understand the underlying functional and structural networks. In mesial temporal lobe epilepsy (MTLE) widespread functional networks are involved in seizure generation and propagation. In this study we have analyzed the spatial distribution of hemodynamic correlates (HC) to interictal epileptiform discharges on simultaneous EEG/fMRI recordings and relative grey matter volume (rGMV) reductions in 10 patients with MTLE. HC occurred beyond the seizure onset zone in the hippocampus, in the ipsilateral insular/operculum, temporo-polar and lateral neocortex, cerebellum, along the central sulcus and bilaterally in the cingulate gyrus. rGMV reductions were detected in the middle temporal gyrus, inferior temporal gyrus and uncus to the hippocampus, the insula, the posterior cingulate and the anterior lobe of the cerebellum. Overlaps between HC and decreased rGMV were detected along the mesolimbic network ipsilateral to the seizure onset zone. We conclude that interictal epileptic activity in MTLE induces widespread metabolic changes in functional networks involved in MTLE seizure activity. These functional networks are spatially overlapping with areas that show a reduction in relative grey matter volumes.

Molecular pathogenesis of polymerase gamma–related neurodegeneration

“…Moreover, although the role of the cerebellum in epileptogenesis remains controversial, studies suggest that it may be secondarily affected by epileptic activity elsewhere in the cortex. Studies of perfusion using single photon emission computed tomography and functional MRI show evidence of increased cerebellar activity during clinical seizures of cortical source and interictally . This suggests that clinical or subclinical cortical epileptic activity may lead to increased metabolic activity in the cerebellum, triggering acute focal lesions locally.…”

Spatial correlation of hemodynamic changes related to interictal epileptic discharges with electric and magnetic source imaging

“…Positive and negative BOLD responses (activations and deactivations) in EEG/fMRI reflect metabolic changes related to the epileptogenic network Laufs and Duncan, 2007]. BOLD responses usually occur in brain regions associated with the generation of IEDs [Benar et al, 2002;Donaire et al, 2013;Thornton et al, 2010], but they are also often seen outside the epileptogenic region [Fahoum et al, 2012;Kobayashi et al, 2006aKobayashi et al, , 2009Wiest et al, 2013]. Deactivation within the epileptic focus is less often observed than activations, and their significance remains not totally understood Kobayashi et al, 2006b;Pittau et al, 2013;van Houdt et al, 2013].…”

Alteration of Interictal Brain Activity in Patients with Temporal Lobe Epilepsy in the Left Dominant Hemisphere: A Resting-State MEG Study

“…Moreover, a recent study combining fMRI and tractography has visualized the propagation of epileptic activity from the temporal epileptogenic focus to the occipital lobe in mesial temporal lobe epilepsy [28]. The involved cortices lie along the occipitotemporal connections supplied by the inferior longitudinal fasciculus, suggesting a direct propagation pathway from the anterotemporal to the occipital lobe [29]. However, in line with previous brain imaging studies we take our data to suggest that the left side epileptic interictal discharges may influence the activity of the bilateral visual cortex in the patients with left temporal lobe epilepsy.…”