Longitudinal study of the cognitive development in children with Williams-Beuren syndrome.

Crisco [1990: Clin Res 38:536A] reported stability of IQs in a group of 14 children with Williams-Beuren syndrome (WBS) over a 5-year period and concluded that they display a development rate similar to normal children. The aim of our study was to examine the stability of the development of nonverbal reasoning abilities over a period of 2 years using two methods. We studied 18 children with WBS (9 girls, 9 boys) with a mean age of 6.6 years (range: 4.4-10.6 yr) at year one (T1), and approximately two years later (T2) at the average age of 8.6 years (range: 5.11-12.7 yr). The Columbia Mental Maturity Scale (CMM) and the Draw A Person Test were administered. The results show that the IQs resulting from the Draw A Person Test were stable over the 2-year period (T1: mean IQ = 63.5, T2: mean IQ = 65, t = 0.63), and display a significant correlation between the two methods (r = 0.547, P = 0.01). Furthermore, the correlation between the two tests (CMM and Draw A Person Test) at the second assessment is high and significant (r = 0.56, P = 0.01). The mean IQs at T2 can be classified as mild mental retardation. A notable result is the significant decrease of the IQs according to the CMM (T1: mean IQ = 77, T2: mean IQ = 68, t = 2.69, P = 0.01). These results suggest that the developmental outcome of children with WBS varies in specific areas of cognitive function over a 2-year period.