Abstracts

Rationale:
For medically refractory epilepsy patients, resective surgery or implantation of neuromodulation devices may afford additional treatment options.  Pre-surgical evaluations including electrophysiology, imaging and neuropsychological (NP) tests assist in identifying epileptogenic foci and networks and limit risk of post-operative cognitive changes. The aim of this study is to determine neuropsychological predictors of surgical outcomes. Understanding the complex relationships between NP variables in dominant and non-dominant hemisphere resections will aid in clinical decision making and allow for individually tailored pre-surgical counseling.
Method:
This is a single center retrospective study of patients who had epilepsy surgery at a level IV epilepsy center. Patients >19 years of age who had resective surgery between 2012 and 2016 and were followed for a minimum of 2-years post-operatively were included. Patients were excluded if they had prior callosotomy or resective surgery, did not have a NP assessment, or had neuromodulation device or required repeat surgery within the 2-year follow-up period. Of the 82 patients who had epilepsy surgery, 47 met formal inclusion and exclusion criteria. A good outcome was defined as an Engel score I. A poor outcome was defined as an Engel score >/= II. Discordance of pre-surgical work-up was defined as any abnormality on EEG, MEG, MRI or intracranial studies that was bilateral or contralateral to the surgical resection. Non-lateralizing NP profiles were not considered to be discordant. Hemispheric dominance was defined by performance on pre-surgical NP assessments.
Results:
Overall, 57.4% (n=27) of study cohort had a good outcome and 42.6% (n=20) had a poor outcome. Pre-surgical work-up was concordant in 48.9% (n=23) and discordant in 51.1% (n=24) of patients. Where pre-surgical data was concordant, 65.2% of patients had a good outcome, compared to 50% of those who had discordant pre-surgical data (p=0.29). Dominant hemisphere resection was performed in 27.7% (n=13) while non-dominant hemisphere resection was performed in 38.3% (n=18) of patients. The remaining 34.0% (n=16) of patients had no hemispheric dominance on NP testing. 61.5% of dominant hemisphere resection patients had a poor outcome, compared to 33.3% of those with non-dominant hemisphere resection, however this difference was not significant (p=0.26). Limitations include small sample size and that post-surgical NP outcomes and quality of life indices were not included.
Conclusion:
In this cohort of medically refractory epilepsy patients who underwent epilepsy surgery, a larger proportion of patients had poorer outcome if their pre-surgical data showed discordance or if they underwent a resection in the dominant hemisphere. However, these results were not statistically significant. We will further explore which specific NP tests may predict post-surgical seizure freedom and NP outcomes.
Funding:
:None.