EEG-fMRI Study Of The Ictal And Interictal Epileptic Activity In Patients With Epilepsy

Purposes: To investigate the map and pattern of Blood Oxygen Level Dependent (BOLD) signal changes correlated to epileptiform discharges with EEG-fMRI in patients with Juvenile Myoclonic Epilepsy or partial epilepsy and the characteristics of the BOLD signal change associated with ictal and interictal epileptiform discharges (IEDs) of JME and then to obtain a greater understanding of pathophysiological mechanisms and brain functional change of JME or partial epilepsy and improve the diagnosis and therapy of them.Methods: Through the method of EEG-fMRI, Forteen patients were studied, six patients with JME and eight patients with partial epilepsy. The BOLD signal changes correlated to epileptiform discharges was investigated in addition to the map and pattern of activation and deactivation in every EEG-fMRI session. The characteristics of BOLD signal changes linked to ictal and interictal epileptiform discharges under different states of consciousness were also explored in the six patients with JME. The relationship between the regions of BOLD signal changes linked to IEDs and the electroclinical localization of epileptogenic zone in patients with partial epilepsy were also studied. Results :1. Six patients with JME were recruited (3 males, 3 females, mean age 13.2, mean onset age 8, range 3-11). The clinical manifestations were: eyelid myoclonus accompanied with absence or not in 4( 3 with tonic clonic seizure), limb myoclonic seizures with absence in 1, limb myoclonic seizures without absence in 1. Interical and ictal EEG have rapid, generalized, often irregular 2-6 Hz spike-waves and polyspike-waves. Nine sessions qualified for the requirements were obtained in all and among them two sessions of BOLD change associated with ictal epileptiform discharges were achieved in two patients. The prominent feature of the regions of BOLD signal changes linked to IEDs was activation and deactivations' bilateral and symmetrical distribution over the cerebral hemispheres. The main regions of activation included thalamus, mesial frontal cortex, middle parietal lobe, temporal lobe, insula, central structures and cerebellum. Deactivation were mainly in the anterior frontal lobe, posterior parietal part and posterior cingulate gyrus where was close to the vicinity of cortex compared with the regions of activation. The distribution of activation associated with ictal epileptiform discharges was more wider and the distribution of deactivation associated with ictal epileptiform discharges was more closer to pericortex compared with that of the BOLD change linked with IEDs. 2. Eight patients with partial epilepsy were recruited (6 males, 2 females, mean age 18.5, mean onset age range 1/2-29) among them three with brain organic lesions. The electroclinical localization were mainly in some 1-2 unilateral brain lobes. Two of the 8 patients who underwent EEG-fMRI were excluded from further analysis: one due to no epileptic discharge, the other due to excessive head motion. Eight sessions of EEG-fMRI scanning in 6 patients were obtained: 6 with activation and deactivation; one with activation only and one deactivation only. 7 sessions showed activations in the brain regions corresponding to electroclinical localization among which 5 sessions showed maximal activations. 5 sessions manifested with weak activations in the opposite side corresponding to lesions in the brain.Conclusions: 1. The activation in thalamus may be associated with GSW of JME; deactivations occurring in anterior frontal areas, parietal regions and posterior cingulate gyrus were inconsistent with a "default" pattern of brain activity in the baseline brain state of activity; the combination of different patterns of activation with consistent deactivations("default" pattern) in patients with JME may prognosticate different types of states of consciousness in response to ictal and interictal epileptic discharges. 2. IED-linked BOLD changes in patients with partial epilepsy were seen in anatomical areas related to the discharges and also in distant brain areas. In most patients with focal epilepsy, positive BOLD response were mainly seen in epileptogenic zones and also in the corresponding Contralateral areas. Deactivations were less associated with IEDs and so it can not reflect the consequential or downstream effects of IEDs on brain activity specifically. 3. Activation areas were well concordant with epileptogenic areas localized by electroclinical findings, so EEG-fMRI is an useful tool to study brain function.