100% of brains of Down's adults over age 40 will show Alzheimer-type neuropathologic changes in the frontal and temporal lobes. In an attempt to image these lesions, magnetic resonance imaging (MRI) was performed in seven patients with Down's syndrome, ranging in age from 17 to 45 years, using a resistive unit operating at 0.15 Tesla. All scans were within normal limits except for one 45 year-old patient with severe left temporal lobe atrophy. No areas of abnormal signal were seen in the frontal or temporal lobes and the white matter lesions commonly seen in elderly demented subjects were not visualized in this group. We conclude that these white matter lesions are likely coincidental and not causally related to Alzheimer's changes. The pathologic process leading to the formation and development of Alzheimer's changes in the brains of Down's adults may not be visible on magnetic resonance images.

Dementia of the Alzheimer type (DAT) has proven to be difficult to diagnose using computerized X-ray tomography (CT). To improve the identification of DAT with CT, several different quantitative approaches have been tried. Brain parenchymal density measurements and a variety of linear indices of ventricular size have failed to reliably separate DAT patients from age matched controls. Measures of ventricular volume improve discrimination, but overlap with controls persists. The inadequacy of a single CT study to diagnose DAT is clearly related to the overlap of brain atrophy in DAT and healthy aging, a finding which has also been noted in post-mortem studies. Estimating the rate of ventricular enlargement from quantitative measurements of ventricular size on successive CT scans may allow the physician to take advantage of the progressive nature of DAT, improving separation of DAT patients from healthy controls.