Structural and Functional Plasticity of Vision in Hydrocephaly
AdvisorCrognale, Michael A.
Electrical and Biomedical Engineering
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Ventriculomegaly and/or increased intracranial pressure with hydrocephalus can cause structural brain abnormalities, which often result in dysfunction. This study utilized diffusion-weighted magnetic resonance imaging (dMRI), anatomical magnetic resonance imaging (MRI), and functional MRI (fMRI) to examine whole-brain connectivity and visual pathways in an adult participant with a history of congenital hydrocephalus and early ventriculoperitoneal shunt placement. An interesting characteristic of this case is that ventricular enlargement was largely confined to one hemisphere, allowing for a degree of within-subject analyses. We first quantified gross changes in morphology by measuring cortical thickness and volumes of gray matter (GM), white matter, (WM) and the ventricles. The findings from regional volume and thickness analysis suggest that the left visual cortex is the most affected region. Our second aim was to characterize and detect abnormal neural connectivity. We used dMRI to trace WM tracts between different brain regions and to construct inter- and intra-hemispheric connectograms. Comparison of the connectometry of the study subject with that from a group of healthy subjects identified deviant pathways in the corpus callosum and occipital regions. The last goal sought to investigate structure and function of the visual pathway from the optic chiasm, via the LGN and through the occipital cortex by combining retinotopic fMRI mapping and dMRI-based tractography. Though visual function was shown to be largely intact, large anomalies in the optic radiation and retinotopy of the left hemisphere was revealed and is likely due to gross morphological distortion and early degeneration. These anomalies however did not equate to an absolute absence of fiber connections. Moreover, the left optic radiation adapted to fit along the ventricular boundary. With regards to our case reported here, we suggest that compensatory neuroplastic reorganization may occur after shunting surgery to support sparing of visual function for optimal neurological recovery.