Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Surgery

Supervisor

Sandrine de Ribaupierre

2nd Supervisor

Roy Eagleson

Co-Supervisor

Abstract

Functional MRI (fMRI) is the only clinically available tool for non-invasive language mapping in children with drug-resistant epilepsy (DRE). Cooperation during the study is low; motion and network immaturity reduce reliability. A combined method with fNIRS, a lower-complexity technique, may cope with some limitations. We developed a combined approach using fNIRS and resting-state fMRI to map children with DRE.

We explored the application and limitations of fMRI and fNIRS in 33 children with DRE. In a subgroup of 12 patients, we conducted a pilot feasibility study to test the fNIRS-guided SEED-based analysis. A higher incidence of atypical language lateralization was observed in all methods. Discrepancies in task-specific lateralization were observed in some participants.

The fNIRS-fMRI combined approach is a novel technique to localize language networks in this population. It may increase accessibility and reliability of children to non-invasive techniques. Larger cohorts and invasive confirmation is needed to further validate this method.

Summary for Lay Audience

Children with drug resistant epilepsy (DRE) may benefit from brain surgery, were the area causing epileptic seizures is removed. In order to find this area and see that areas of the brain with important function (such as language) don’t overlap, they have to undergo multiple tests where they have to remain still and even collaborate. This is challenging, since often, they cannot do it. They get scared, distracted or don’t understand the instructions. To overcome this problem, we propose using newer, less invasive technologies such as functional MRI (fMRI) and functional near-infrared spectroscopy (fNIRS). These technologies look at the activation of certain brain areas when they are functioning.

Both fMRI and fNIRS have been studied separately in the field of epilepsy and despite its great potential, conflicting results were found. More studies are required to fully allow these methods to be introduced to epilepsy surgery patients.

The objective of this study was to assess fMRI and fNIRS separately and then combined to see if they are useful to 1) localize where seizures are originating and 2) if critical brain areas overlap with it.

Children of ages 6 to 18 with DRE that are candidates for epilepsy surgery underwent fMRI & fNIRS sessions with specific tasks to activate language. For the first objective, we were able to corroborate many of the problems that usually appear when doing these sorts of studies, therefore confirming the need to continue with research in this field. For the second objective, we used the information from the fNIRS to guide a statistical analysis of the fMRI while the children were at rest. We were able to identify language areas in these children. Our results were partially concordant with the other studies. However, it is still unknown which study was the correct one to determine language.

We concluded that combining different non-invasive methods may be a new way to try to overcome some of the problems we currently have. Further testing and confirmation through invasive studies will eventually determine which of these methods is more accurate.

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Available for download on Sunday, September 01, 2024

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