Optical coherence tomography in people with epilepsy : symmetry and clinical correlations

• Main Author: Bartmann, Ana Paula
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2019
• Subjects: Asymmetry; Epilepsy; Hypotheses; Tomography

Optical Coherence Tomography (OCT) provides detailed images by assessing the scattering properties of a tissue (1)⁠. OCT is precise and easily repeatable. It is quick to obtain and does not cause any significant discomfort to patients. For these reasons, it is a useful clinical tool to diagnose and monitor many conditions. Peripapillary retinal nerve fibre layer (pRNFL) thickness measured by OCT was recently confirmed as a biomarker of white matter (WM) integrity in various neurological conditions (2)⁠. In epilepsy, retinal thinning is found in people exposed to vigabatrin (3)⁠ but also in people not exposed to this antiepileptic drug (AED), particularly in cases where drug-resistance or intellectual disability are present (4)⁠. I have reviewed and expanded these analyses. I tested the hypothesis that OCT is useful in identifying changes associated with different epilepsy syndromes by identifying changes in specific retinal segments related to retrograde trans-synaptic degeneration of areas in the brain. Though thinning was present, it did not reach statistical significance when I analysed the different cerebral lobes of onset. The rate of pRNFL thinning in people with epilepsy is yet unknown. I have identified a strong effect of age in this cohort and hypothesise that this might be related to disease progression. Longitudinal studies starting at the time of diagnosis are necessary to confirm this hypothesis. I assessed if pRNFL thickness asymmetry could correlate to seizure focus and widespread neuronal damage. This complex analysis seems to show that people with epilepsy present with asymmetry in inferior segments of the optic nerve head (ONH). It is possible that this finding could become useful to help phenotype epilepsy syndromes. I analysed the correlation between brain volume and retinal thickness and identified a statistically significant association with thalamic volume. This result needs to be further explored. I also analysed the effect of AED exposure to assess whether, as seen with vigabatrin, this correlates with changes in retinal thickness. The analysis failed to identify any relation between drug exposure and pRNFL thickness, but the insufficient number of people exposed to certain AEDs limited the analysis.