Spikes and High Frequency Oscillations in Lateral Neocortical Temporal Lobe Epilepsy: Can They Predict the Success Chance of Hippocampus-Sparing Resections?

Purpose: We investigated the distribution of spikes and HFOs recorded during intraoperative electrocorticography (ioECoG) and tried to elaborate a predictive model for postsurgical outcomes of patients with lateral neocortical temporal lobe epilepsy (TLE) whose mesiotemporal structures are left in situ.

Methods: We selected patients with temporal lateral neocortical epilepsy focus who underwent ioECoG-tailored resections without amygdalo-hippocampectomies. We visually marked spikes, ripples (80-250 Hz), and fast ripples (FRs; 250-500 Hz) on neocortical and mesiotemporal channels before and after resections. We looked for differences in event rates and resection ratios between good (Engel 1A) and poor outcome groups and performed logistic regression analysis to identify outcome predictors.

Results: Fourteen out of 24 included patients had a good outcome. The poor-outcome patients showed higher rates of ripples on neocortical channels distant from the resection in pre- and post-ioECoG than people with good outcomes ( p pre = 0.04, p post = 0.05). Post-ioECoG FRs were found only in poor-outcome patients ( N = 3). A prediction model based on regression analysis showed low rates of mesiotemporal post-ioECoG ripples (OR mesio = 0.13, p mesio = 0.04) and older age at epilepsy onset (OR = 1.76, p = 0.04) to be predictors of good seizure outcome.

Conclusion: HFOs in ioECoG may help to inform the neurosurgeon of the hippocampus-sparing resection success chance in patients with lateral neocortical TLE.