Early Increases in Hippocampal Synchrony Predict Chronic Epileptiform Burden in a Temporal Lobe Epilepsy Model
Temporal lobe epilepsy (TLE), the most common focal epilepsy, is often drug-resistant and arises predominantly in the hippocampus. Disease severity is conventionally assessed by seizure frequency and duration, yet epileptiform activity outside discrete seizures may also track disease progression. Whether this activity reflects hippocampal network reorganization as part of epileptogenesis, and…
A temporal lobe epilepsy model revealed that early increases in hippocampal synchrony can predict chronic epileptiform activity. Temporal lobe epilepsy, a drug-resistant condition originating in the hippocampus, is typically assessed by seizure frequency and duration. However, epileptiform activity outside of discrete seizures may also indicate disease progression.
While the relationship between this activity and epileptogenesis is unclear, a study combined two-photon calcium imaging of hippocampal CA1 neurons with repeated EEG recordings over 16 weeks in pilocarpine-treated mice. The imaging showed acutely rising CA1 firing and synchrony, which decreased during a latent period and then increased again chronically.
The synchronized firing formed brief waves that propagated in a consistent direction. Epileptiform burden followed a similar trajectory and increased with chronic seizures, leading to electrographic seizures. CA1 synchrony correlated with epileptiform burden and categorized mice into distinct groups with varying neuronal and electrographic outcomes.
Importantly, CA1 synchrony measured within three weeks of pilocarpine induction could predict chronic epileptiform burden, suggesting that early hippocampal synchrony could serve as a potential imaging biomarker. This discovery also implies an early window of opportunity for intervention in temporal lobe epilepsy.
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