[Two cases of adult Down's syndrome presenting parietal low uptake in 123I-IMP-SPECT].

We performed 123I-IMP-SPECT to patients with Down's syndrome who were supposed to have neuropathological findings of dementia of the Alzheimer's type. In case 1, a 52-year-old man with dementia, bilateral posterior parietal low uptake and right temporal low uptake were noted. Uptake was markedly lower in the right hemisphere. Case 2, a 38-year-old man not exhibiting clinical features of dementia, presented slightly decreased uptake in bilateral posterior parietal areas. We conclude that the patterns of abnormally decreased uptake in these cases of Down's syndrome are similar to those in dementia of Alzheimer's type, and that there is a possibility to detect the predemented stage of Down's syndrome by 123I-IMP-SPECT.