Longitudinal changes in brain CT scans and development of dementia in Down's syndrome.

To determine the relationship of the development of dementia to longitudinal changes in brain CT scans in patients with Down's syndrome (DS), we studied 14 Japanese DS patients at an interval of 10 years. The age at entry to the study was 35.7 +/- 9.9 (mean +/- SD) years in 1989 when we did the first CT scans. We performed the second CT scans in 1999 and quantitatively compared them with those taken in 1989. The 4 oldest of the patients (the demented group, 55.3 +/- 1.4 years of age in 1999) developed symptoms of cognitive decline before 1999. The younger 10 (the non-demented group, 41.9 +/- 9.0 years of age in 1999) remained stable in cognitive function until 1999. Despite the clear difference between the demented and the non-demented group in brain atrophy in 1999, CT measures of the demented group were similar to those of the non-demented group in 1989. These results indicate that age is a better predictor of dementia than imaging studies and that CT does not show a quantitative difference between the demented and the non-demented group before the onset of dementia.