Voxel-based analysis of cerebral glucose metabolism in mono- and dizygotic twins discordant for Alzheimer disease.

BACKGROUND: Sporadic Alzheimer disease (AD) is a multifactorial disease to which both genetic and environmental factors contribute. Therefore, twin pairs are useful in studying its pathogenesis and aetiology. Cerebral glucose metabolism has been found to be reduced in AD patients. METHODS: Cerebral glucose metabolism was studied in seven monozygotic (MZ) and nine same-sexed dizygotic (DZ) twin pairs discordant for AD using positron emission tomography. To obtain objective and explorative results concerning differences in glucose metabolism, the analysis was performed utilising modern voxel-based analysis methodology statistical parametric mapping and automated region-of-interest analysis. RESULTS: In the demented MZ and DZ co-twins, cerebral glucose metabolism was extensively reduced compared with controls. The non-demented MZ co-twins showed reduced metabolism in inferior frontal, lateral temporal, parietal and medial temporal cortices as well as in the thalamus, putamen and right amygdala. In contrast, no reductions were found in the non-demented DZ co-twins. The reduction found in the non-demented MZ co-twins may be an indicator of genetic susceptibility to AD.