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----------------------------------------------------------------- PET Scan May Detect Presymptomatic Changes In Alzheimer's Disease ----------------------------------------------------------------- WESTPORT, Aug 01 (Reuters) - Positron emission tomography (PET) may be able to detect preclinical changes in brain glucose metabolism in persons at risk for Alzheimer's disease. Such an early diagnostic test could identify patients who might benefit most from treatments, once they become available, to prevent or delay the onset of dementia. Dr. Pietro P. Pietrini of the National Institute on Aging in Bethesda, Maryland, and colleagues examined regional cerebral glucose metabolism by PET in 16 adult nondemented patients with trisomy 21. The researchers point out that, because such subjects inevitably develop Alzheimer's neuropathology after the age of 40, they "...provide a unique human model to investigate the preclinical phases of Alzheimer's disease." Half the subjects were around 36 years of age and half were older, about 50. At rest, the younger and older patients demonstrated similar patterns of glucose metabolism in all cerebral regions. During audiovisual stimulation, however, the investigators found that "...older nondemented subjects with Down's syndrome have significantly lower rates of regional cerebral glucose metabolism...than do younger subjects with Down's syndrome." The parietal and temporal regions showed the greatest differences in glucose metabolism between the younger and older Down's syndrome patients. These same regions are "...most vulnerable to Alzheimer's disease neuropathology and the first to show abnormal brain metabolism in Alzheimer's disease," the authors explain. Moreover, this pattern suggests that the decline in glucose metabolism is not attributable to the normal aging process, because this occurs mainly in the frontal lobes. Overall, the researcher conclude, the findings suggest that "...abnormal brain metabolism in subjects at risk for developing dementia can be revealed before the appearance of nonmemory cognitive decline or clinical dementia." Am J Psychiatry 1997;154:000-000. Copyright 1997 Reuters Limited. <http://www.reutershealth.com/news/docs/199708/19970801clc.html> ----------------------------------------------------------------- [log in to unmask]