AbstractWilliams syndrome (WS) is a genetic disorder that results in a wide variety of impairments, involving most of the areas of development. Although significant variability has been found among children with Williams syndrome in terms of the phenotype, the idea of a typical WS profile is still predominant in the literature. However, the clinically observed widespread differences have caused clinicians to often speak about partial deletions, atypical deletions or inconclusive cases. In addition, some researchers have put forward the notion that the size of
the deleted area might have an influence in both quantitative and qualitative aspects of the phenotypical characteristics..
This thesis explores the differences in cognitive ability and attainment of developmental milestones in children with WS. Four experimental studies have been conducted involving a total number of 74 children between the ages of few months to the age of 18 years. Study 1 investigated the effect of deletion size in
the cognitive ability of WS children, as this was measured by 4 different IQ tests.
Study 2 examined the effect of deletion size in the attainment of developmental milestones, Study 3 examined the longitudinal course of IQ in children with WS and Study 4 examined a clinically observed de novo phenomenon of a strong leftward bias affecting attention and short term visuospatial memory.
Studies 1 and 2 demonstrated an effect of deletion size on the cognitive abilities of children with WS. The greater the deletion size in the 7qll.23 area, the lower the performance on measures of cognitive ability and the longer and more problematic the attainment of developmental milestones.
Study 3 indicated that there is a significant increase in the IQ scores of children with the typical deletion. The IQ scores remain however to the mild/moderate retardation - low average area of the IQ scale. Study 4 examined and tried to offer explanatory ideas in a de novo clinically observed phenomenon of a leftward bias affecting attention and visuospatial short term memory. Children with WS encountered great difficulty in detecting and remembering the position of items presented to the right side of a presentation matrix.
These findings suggest that deletion size has an influence on both performance on measures of cognitive ability and attainment of developmental milestones, the cognitive ability of children with WS significantly improves with advance of chronological age and that there is a leftwards bias affecting attention and short
term visuospatial memory.
|Date of Award
|Ian Stuart-Hamilton (Supervisor) & Peter Mayer (Supervisor)
- Williams syndrome