Seizure Freedom After Epilepsy Surgery and Higher Baseline Cognition May Be Associated With a Negatively Correlated Epilepsy Network in Temporal Lobe Epilepsy.

Elliot G Neal,Mike R Schoenberg,Fernando L Vale,Yarema B Bezchlibnyk,Stephanie Maciver

doi:10.3389/fnins.2020.629667

Elliot G Neal, Mike R Schoenberg + Show 3 more

Open Access

https://doi.org/10.3389/fnins.2020.629667

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Abstract

Background: Brain regions positively correlated with the epileptogenic zone in patients with temporal lobe epilepsy vary in spread across the brain and in the degree of correlation to the temporal lobes, thalamus, and limbic structures, and these parameters have been associated with pre-operative cognitive impairment and seizure freedom after epilepsy surgery, but negatively correlated regions have not been as well studied. We hypothesize that connectivity within a negatively correlated epilepsy network may predict which patients with temporal lobe epilepsy will respond best to surgery.Methods: Scalp EEG and resting state functional MRI (rsfMRI) were collected from 19 patients with temporal lobe epilepsy and used to estimate the irritative zone. Using patients’ rsfMRI, the negatively correlated epilepsy network was mapped by determining all the brain voxels that were negatively correlated with the voxels in the epileptogenic zone and the spread and average connectivity within the network was determined.Results: Pre-operatively, connectivity within the negatively correlated network was inversely related to the spread (diffuseness) of that network and positively associated with higher baseline verbal and logical memory. Pre-operative connectivity within the negatively correlated network was also significantly higher in patients who would go on to be seizure free.Conclusion: Patients with higher connectivity within brain regions negatively correlated with the epilepsy network had higher baseline memory function, narrower network spread, and were more likely to be seizure free after surgery.

Highlights

Surgical Treatment of Temporal Lobe EpilepsyEpilepsy is a common primary neurological disorder that affects 0.5–1% of the global population, of which 20–30% are refractory to medical management (Kwan and Brodie, 2000; Sander, 2003)
If the epilepsy is focal and the epileptogenic zone can be localized to a temporal lobe using conventional techniques, which include electroencephalography (EEG), MRI, 18Fluoro-2-deoxyglucose positron emission tomography [(18F-FDG) PET], semiology, and neuropsychological testing, a surgery can be planned to resect or ablate the hypothesized focus and disconnect the epileptogenic network
We have previously described a positively correlated “epilepsy network,” defined as the network of regions with activation patterns that have a high degree of positive correlation with the epileptogenic zone in patients with temporal lobe epilepsy, and we hypothesized that the negatively correlated regions might be important in understanding the brain function of the patient with temporal lobe epilepsy

Summary

Introduction

Surgical Treatment of Temporal Lobe EpilepsyEpilepsy is a common primary neurological disorder that affects 0.5–1% of the global population, of which 20–30% are refractory to medical management (Kwan and Brodie, 2000; Sander, 2003). Resective surgeries in the temporal lobe have been shown to result in seizure freedom in approximately two-thirds of patients, and an improved quality of life when compared to medical management alone (Wiebe et al, 2001; Bell et al, 2009; Engel et al, 2012; Vale et al, 2012). This still leaves the one-third of patients who undergo surgery in their temporal lobe who continue to have debilitating seizures. We hypothesize that connectivity within a negatively correlated epilepsy network may predict which patients with temporal lobe epilepsy will respond best to surgery

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