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Recent advances in brain imaging have led to a breakthrough in pinpointing where seizures start in the brain. Our study combines two powerful techniques—EEG and fMRI—to improve how we locate the exact areas responsible for seizures in patients with epilepsy. By focusing on high-frequency brain waves, called high frequency oscillations (HFOs), and their interaction with other electrical disturbances on EEG, we aimed to enhance the accuracy of epilepsy surgery planning.

We studied 45 patients with epilepsy who had electrodes implanted in their brains to monitor electrical activity. While these patients were in an MRI scanner, we used EEG to detect HFOs, which are events that are thought to be precursor events to seizures. We also looked at how these HFOs related to other epileptic tissue marker events called interictal epileptiform discharges (IEDs). Using fMRI, we then mapped the brain's activity during these events to see which brain regions were active when they were occurring. 

We found that not only do HFOs cooccurring with IEDs produce unique activation maps, but the resulting fMRI maps show increased activity in areas much closer to the electrodes where HFOs are observed from compared to fMRI maps correlated with HFOs alone. Even more importantly, activation maps associated with HFOs and IEDs together were more discrete and had greater activation than activation maps associated with HFOs alone. Therefore, we show that considering cooccurring HFOs and IEDs can allow for the creation of clearer fMRI activation maps that can be used to better localize seizure generating tissue.