Nasheha Baset

ORCID Identifier(s)

0000-0001-5693-8397

Graduation Semester and Year

2021

Language

English

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Bioengineering

First Advisor

George Alexandrakis

Second Advisor

Christos Papadelis

Abstract

Abstract Exploring Imaging Technology in the Diagnosis and Treatment of Pediatric Medically Refractory Epilepsy with Intracranial Electroencephalography and Post-Surgical Evaluations Nasheha Baset, MS The University of Texas at Arlington, May 2021 Supervising Professor: Dr. Christos Papadelis Epilepsy is a disorder that commonly causes seizures due to abnormal neurological activity, which can disrupt daily life. Of all patients with epilepsy, 60% suffer from focal epilepsy. Approximately 15% of these cases are considered to be drug resistant, or refractory, as the patient is not responsive to a combination of two or more anti-epileptic drugs (AED). Traditionally, approaches to treatment of medically refractory epilepsy include lobotomies, resections, or surgical severing of nerves in the cortex, in order to achieve seizure freedom. These risks include, but are not limited to, higher risk of infection due to its invasive nature, possible consequences of changes to their personality, and possible changes to their intellectual functions. For this reason, laser ablations are becoming more popular as they greatly reduce discomforts, recovery time, and morbidity being greatly reduced compared to traditional resections. Children are different than their adult counterparts in that seizure frequency typically tends to be higher in children than adults, and that the child’s brain is very neuroplastic and reorganizing as they grow. The Seizure Onset Zone (SOZ) is the area also in the cortex where the epileptiform discharges are generated when localized by a scalp or intracranial electroencephalogram (iEEG). The Resection Zone (RZ) is the region that resected or ablated during surgery to optimally reduce seizure occurrence. The Epileptogenic Zone (EZ) is the minimum area of the cortex that would need to be resected or ablated to allow for seizure freedom. IEEG, or intracranial electroencephalogram, measures the electric potential directly from the brain’s surface using electrocorticography (ECOG) electrodes and stereotactic EEG (SEEG). Functional connectivity (FC) is defined as the study of temporal connections between spatially distinct neurophysiological events. To evaluate the efficacy of the laser ablation procedure, we retrospectively analyzed the medical records from 36 children with medically refractory epilepsy who have undergone epilepsy surgery with laser ablation at Cook Children’s Health Care System. We examined the surgical outcome of the patients by their post-surgery Engel scores and the number of AEDs, and conducted t-tests to evaluate differences. To develop the interictal functional connectivity biomarker of the Epileptogenic Zone, we analyzed iEEG data from 19 patients with medically refractory epilepsy undergone resective surgery (13 with good surgical outcome and 6 with poor surgical outcome) from Boston Children’s Hospital. We filtered the iEEG data in the following frequency bands: 1-70 Hz for spikes, and 80-250 Hz for ripples, and both 1-70 Hz and 80-250 Hz for simultaneous spike and ripple events. Then, we estimated the following functional connectivity matrixes: AEC, PLV, and CORR. We compared these functional connectivity measures for electrodes inside the Seizure Onset Zone and the Resection Zone and performed statistical analysis between these measures using Wilcoxon signed-rank test. Due to the small cohort for the evaluation of AEDs before the laser ablation study, many tests did not meet the requirements to be run, and for the tests that did meet the requirements, significant results were not found in all, but one test (p-value = 0.000574, α = 0.05). For the functional connectivity study using iEEG data to identify the Epileptogenic Zone, significant results were not found in all, but two of the tests, first when comparing the inside and the outside regions of the Seizure Onset Zone in poor outcome patients using CORR (80-250Hz) (p-value = 0.03125, α = 0.05) and comparing the inside to the outside regions of the Resection Zone in good outcome patients using CORR (1-70 Hz) (p-value = 0.03979, α = 0.05). These results do not support the current literature, leading to the conclusion that expanding the cohort of the AED and ablation study, and reevaluating the methodology of the functional connectivity of the Epileptogenic Zone study will not only open more doors as to how we can improve the localization of epilepsy, but also provide a better understanding of the diagnoses and treatment of this disease as well. Although we rejected our initial hypothesis, we now know that there is great promise in modifying and continuing these studies long term.

Keywords

Epilepsy, Imaging, Neurology, Electroencephalography, Functional connectivity, Robot-assisted stereotactic laser ablation

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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