Rationale:
Current approaches to recording epileptic activity often require multiple electrodes, depending on the location, number, and dynamics of seizure foci. This can be invasive and technically complex. White matter tracts, such as the corpus callosum (CC) and fimbria, which connect broad cortical and hippocampal regions, may offer a less invasive alternative for detecting widespread epileptic activity. This study investigates the feasibility of using a single electrode placed in the CC or fimbria to detect and monitor epileptic activity across both hemispheres and evaluates its potential for closed-loop epilepsy management.
Methods:
We employed both in vitro (4-aminopyridine bath and focal epilepsy models) and in vivo (4-AP focal epilepsy) models to induce epileptic activity. Recording electrodes were placed in the CC and cortex, or in the fimbria and CA1 region of the hippocampus. We analyzed the ability of white matter electrodes to detect epileptic discharges originating from either hemisphere. Additionally, we examined interhemispheric propagation of epileptic activity via white matter recordings. Root Mean Square (RMS) analysis of CC signals was used to quantify correlations with seizure progression.
Results:
A single electrode placed in the white matter (n = 5 in vivo; n = 10 in vitro) reliably detected epileptic activity originating from cortical or hippocampal regions in one or both hemispheres. White matter recordings clearly captured the propagation of epileptic discharges between hemispheres. RMS values from CC recordings increased in parallel with seizure intensity, supporting their use for quantitative seizure monitoring.
Conclusions:
White matter recordings via a single electrode provide a novel, efficient method for detecting and monitoring epileptic activity across large cortical and hippocampal territories. This approach reduces the need for multiple electrodes and precise localization of seizure foci. The correlation between RMS values and seizure severity further supports the utility of this method for real-time monitoring and closed-loop therapeutic interventions, particularly in conjunction with low-frequency white matter stimulation strategies.
Funding:
Research reported in this publication was supported by the National Institute of Neurological Disorders and Stroke of the National Institutes of Health under award number R01NS114120.