Abstract
Williams syndrome (WS) is a rare genetic neurodevelopmental disorder characterized by increased non-social anxiety, sensitivity to sounds and hypersociability. Previous studies have reported contradictory findings with regard to regional brain variation in WS, relying on only one type of morphological measure (usually volume) in each study. The present study aims to contribute to this body of literature and perhaps elucidate some of these discrepancies by examining concurrent measures of cortical thickness, surface area and subcortical volume between WS subjects and typically-developing (TD) controls. High resolution MRI scans were obtained on 31 WS subjects and 50 typically developing control subjects. We derived quantitative regional estimates of cortical thickness, cortical surface area, and subcortical volume using FreeSurfer software. We evaluated between-group ROI differences while controlling for total intracranial volume. In post-hoc exploratory analyses within the WS group, we tested for correlations between regional brain variation and Beck Anxiety Inventory scores. Consistent with our hypothesis, we detected complex patterns of between-group cortical variation, which included lower surface area in combination with greater thickness in the following cortical regions: post central gyrus, cuneus, lateral orbitofrontal cortex and lingual gyrus. Additional cortical regions showed between-group differences in one (but not both) morphological measures. Subcortical volume was lower in the basal ganglia and the hippocampus in WS versus TD controls. Exploratory correlations revealed that anxiety scores were negatively correlated with gray matter surface area in insula, OFC, rostral middle frontal, superior temporal and lingual gyrus. Our results were consistent with previous reports showing structural alterations in regions supporting the socio-affective and visuospatial impairments in WS. However, we also were able to effectively capture novel and complex patterns of cortical differences using both surface area and thickness. In addition, correlation results implicate specific brain regions in levels of anxiety in WS, consistent with previous reports investigating general anxiety disorders in the general population.
Highlights
Williams syndrome (WS) is a rare genetic neurodevelopmental disorder caused by a microdeletion of approximately 25 genes on chromosome 7q11.23
Many WS subjects are literate, to allow for consistent administration, regardless of reading level, the Beck Anxiety Inventory was administered to each WS participant by reading the items out loud and asking for a verbal response, which was recorded by the trained interviewer
For all cortical regions showing significant group differences in morphology, we observed a consistent pattern of lower surface area (SA) and greater cortical thickness (CT), in some cases, only one measure reached significance for a given region of interests (ROIs)
Summary
Williams syndrome (WS) is a rare genetic neurodevelopmental disorder caused by a microdeletion of approximately 25 genes on chromosome 7q11.23. Previous magnetic resonance imaging (MRI) studies that employed automated methods, such as voxel-, tensor- or deformation-based morphometry, consistently showed reduced grey matter volume in the intraparietal sulcus, occipitoparietal sulcus, brain stem and occipital lobe regions in WS versus TD controls [12,13,14,15]. Other regional differences, such as in the orbitofrontal cortex (OFC), superior temporal gyrus, insula and the anterior cingulate cortex are often reported inconsistently across studies, with some studies reporting greater grey matter volume and others reporting less or no differences [9,10,12,13,14,15]. A surface-based analysis by Van Essen et al [17] reported reductions in sulcal depth in the cingulate, frontal operculum, and anterior and posterior intraparietal regions, along with increases in sulcal depth in the hippocampus, cuneus, angular gyrus, superior temporal gyrus, medial frontal gyri, and parietooccipital regions
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