[Correlative study of the brain CT and clinical features of patients with Down's syndrome in three clinical stages of Alzheimer type dementia].

Patients with Down's syndrome often develop Alzheimer type neuropathological changes as well as dementia of the Alzheimer type after the age of 40. We studied brain CT findings in relation to three clinical stages of Alzheimer type dementia in 11 patients with Down's syndrome aged from 17 to 55 years. In addition, 123I-IMP-SPECT was studied in 4 of these patients. Dementia of the Alzheimer type was present in 9 patients; 5 patients were in the early stage, 2 were in the progressive stage, and the other 2 were in the end stage. The earliest CT finding was enlargement of the suprasellar cistern, which indicated atrophy of the medial temporal lobe including the hippocampus and amygdala. This finding was not present in non-demented individuals with Down's syndrome. Moreover, CT scans showed that brain atrophy progressed to the temporal, frontal lobe, and then generalized cerebral cortices, which correlated clinically with the severity of dementia. Studies of 123I-IMP-SPECT in two patients with mild dementia revealed abnormally decreased isotope uptake in the temporal and posterior parietal regions. We suggest to measure the size of the suprasellar cistern in CT and SPECT scans for early detection and diagnosis of mild dementia of the Alzheimer type in patients with Down's syndrome.