Authors :
Presenting Author: Isha Snehal, MBBS – University of Nebraska Medical Center
Josh Matyi, PhD – Department of Neurological Sciences – University of Nebraska Medical Center; Matthew Garlinghouse, PhD – Assistant Professor, Department of Neurological Sciences, University of Nebraska Medical Center; Kevin Tyner, B.S. – Department of Neurosurgery – University of Nebraska Medical Center; Matthew McCumber, M.S. – Department of Neurosurgery – University of Nebraska Medical Center; Stephen Gliske, PhD – Associate Professor, Department of Neurosurgery, University of Nebraska Medical Center; Makayla Schissel, M.P.H – Department of Biostatistics – University of Nebraska Medical Center; Hesham Ghonim, MD – Assistant Professor, Department of Neurological Sciences, University of Nebraska Medical Center; Olga Taraschenko, MD, PhD – Associate Professor, Director, Comprehensive Epilepsy Program, Department of Neurological Sciences, University of Nebraska Medical Center
Rationale:
Research in patients with medically refractory epilepsy shows that extending the resection to include zone of seizure spread may result in better postoperative seizure control. However, the relationship between the speed of seizure propagation and post-operative seizure control has not been previously studied. Our study examines the relationship between speed of seizure spread and seizure control after resection, and the performance on presurgical IQ testsMethods:
Retrospectively, we reviewed electronic medical records (EMRs) and intracranial EEGs of patients with medically refractory epilepsy who underwent epilepsy surgery at University of Nebraska Medical Center in 2008-2016. Demographics, scores on Wechsler Adult Intelligence Scale (WAIS-IV) and Wechsler Abbreviated Score of Intelligence (WASI-II), including General Adult Intelligence Standard Score (GAI), Full-Scale Intelligence Quotient (FSIQ), Verbal Comprehension Index (VCI), and Perceptual Reasoning Index (PRI), were recorded and Engel scores at two year post-surgical visit extracted. Presurgical intracranial EEG (iEEG) tracings were reviewed by epileptologists to denote seizure onset and early vs. late seizure spread. Early spread was defined as propagation within two or more surrounding contacts on the grid within ten seconds from seizure onset. In addition, time-frequency analysis was performed, and frequency range of interest was identified. Power of all channels at +/- 1 Hz was identified. Channels within ten sec from seizure onset with power greater than mean + 2 SD of identified channel for two or more consecutive epochs (epochs =1 sec with 0.5-sec overlap) were noted.Results:
Among 45 patients, 71.1% were female. The mean age at surgery was 37.7 ± 12.8 yrs. On visual analysis, 20 (44.4%) had early, 16 (35.5%) had late, and 9 (20%) had absent spread. Engel scores of one, two, three, and four were found in 19 (55.9%), 4 (11.8%), 4 (11.8%), and 7 (20.6%) of patients, respectively. Mean (Standard Deviation) GAI/FSIQ, VCI and PRI scores in patients with early spread were 84.44 (12.61), 85.81 (11.71), and 87.06 (16.60). There were no statistically significant differences between early and late spread groups regarding performance on these tests (p=0.29, p=0.19, and p=0.73, respectively, t-tests). There was also no association between early/late spread and Engel score distribution (p=0.87, Fischer exact test). The signal processing algorithm was consistent with clinical categorization of early vs. late spread in 78.5% of seizures.
Conclusions:
This study suggests that early seizure spread in medically refractory epilepsy may not affect patients’ performance on IQ tests or determine rates of their postoperative seizure freedom. The signal processing algorithm analyzing seizure spread on iEEG can be applied to supplement visual analysis of seizures. This method will be applied to other cognitive domains, including memory and language, in the future.
Funding:
O.T. received salary & research support from the NIH P20GM130447 CONDA Award & Nebraska Stem Cell Grant