Abstracts

Rationale: Genetic generalized epilepsy (GGE) is a heterogeneous condition comprising approximately 20% of all epilepsy cases. One of the most common electroclinical syndromes of GGE is juvenile myoclonic epilepsy (JME). Advances in neuroimaging techniques, particularly fMRI, have provided insight into the epileptic networks of GGE and JME. Although MEG data regarding GGE is limited, advanced source modeling with MEG may provide further understanding of the complex networks involved in GGE and JME. This study evaluated 4 patients with a clinical diagnosis of GGE who underwent a resting-state MEG study. Methods: Four patients (3 female) with a clinical diagnosis of GGE and JME were evaluated using a 148 channel MEG: Magnetometers and simultaneous 32 channel EEG. Data were visually inspected for epileptiform activity in both the EEG and MEG. Source analysis was performed with equivalent current dipole (ECD) and coherence source imaging (CSI), which is a measure of the synchronicity of the oscillating neurons. CSI localizations were then used as a seed for diffusion tensor imaging (DTI). DTI fibers obtained from a standardized DTI atlas were used to link highly coherent areas in the brain. All analytical tools are available freeware at: www.megimagin.com. Results: The average age of the 4 patients was 21 years old (range 12-30 years old). The mean duration of epilepsy was 15.8 years (range of 9-22 years). Two patients experienced absence, myoclonic, and generalized tonic-clonic seizures, while the other 2 patients had myoclonic and generalized tonic-clonic seizures. Only 1 patient was seizure free, while 3 were on an average of 4 seizure medications. Photosensitivity was documented in only 1 patient. The MEG and EEG results are presented in Table 1. All 4 patients had generalized polyspike-and-wave discharges on EEG and MEG with ECD mapping of the MEG data to either the right or left frontal cortex. Although CSI was also localized to the frontal cortex, CSI with DTI revealed a diffuse network emanating from the frontal cortex with connections throughout the bilateral hemispheres. Areas of high coherence were linked between the frontal and occipital cortex in 3 patients. However, the patient with photosensitivity (patient 1) demonstrated the highest coherence between these 2 regions (Fig 1). Conclusions: The combination of MEG with advanced source modeling can provide information regarding epileptic networks in people with GGE and JME. These findings are consistent with previous MEG and fMRI studies in GGE and JME and are suggestive of a source within the frontal cortex. The different patterns of CSI and DTI may suggest different epileptic networks are involved in different syndromes of GGE and subsyndromes of JME. More patients with GGE and JME are necessary to further elucidate the epileptic networks involved in these conditions.