Regional Cerebral Glucose Metabolism is Normal in Young Adults with down Syndrome

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Abstract
Regional CMRglc (rCMRglc) values were measured with [18F]2-fluoro-2-deoxy-d-glucose (18FDG) and positron emission tomography (PET), using a Scanditronix PC-1024-7B scanner, in 14 healthy, noninstitutionalized subjects with trisomy 21 (Down syndrome; DS) (mean age 30.0 years, range 25–38 years) and in 13 sex-matched, healthy volunteers (mean age 29.5 years, range 22–38 years). In the DS group, mean mental age on the Peabody Picture Vocabulary Test was 7.8 years and dementia was not present. Resting rCMRglc was determined with eyes covered and ears occluded in a quiet, darkened room. Global gray CMRglc equaled 8.76 ± 0.76 mg/100 g/min (mean ± SD) in the DS group as compared with 8.74 ± 1.19 mg/100 g/min in the control group (p > 0.05). Gray matter regional measurements also did not differ between groups. The ratio of rCMRglc to global CMRglc, calculated to reduce the variance associated with absolute rCMRglc, and right/left ratios did not show any consistent differences. These results show that healthy young DS adults do not have alterations in regional or global brain glucose metabolism, as measured with 18FDG and PET, prior to an age at which the neuropathological changes in Alzheimer disease are reported to occur.