Nodular heterotopia and absence seizures: fMRI evidence that they may be connected

• Two patients were identified with absence seizures (AS).
• Subjects had co-existent and peri-ventricular nodular heterotopia (PNH).
• EEG fMRI was used to explore the potential association between PNH and AS.
• The PNH displayed connectivity to the typical absence network.
• This study demonstrates that fMRI may be used to understand complex networks.

SummaryIn this study we used EEG-fMRI to investigate whether peri-ventricular nodular heterotopia (PNH) are connected to the seizure generating network in individuals initially diagnosed with absence seizures (AS) who were later found to have co-existent PNH. We performed event related EEG-fMRI of the patients typical events as well as performing functional connectivity (FC) seeded from the PNH to answer this question. Both subjects demonstrated event related BOLD change in the “core” absence network. Subject 1 also displayed event related BOLD increase in the nodules while FC analysis demonstrated connectivity between the nodules and the thalami and striatum bilaterally. The second subject did not display event related BOLD in the PNH but FC analysis demonstrated strong connections between the PNH and the parietal cortex. This study demonstrates that the peri-ventricular nodules can show connectivity to the absence network in individuals with AS and may be involved in seizure generation.