Striatal dopamine metabolism correlated with frontotemporal glucose utilization in Alzheimer's disease: a double-tracer PET study.

We previously found that the rate of [l8F]6-fluoro-L-dopa (FDOPA) uptake into the striatum (the Ki value) in Alzheimer's disease (AD) correlated with cognitive function. Patients with wandering behavior had an increased level of D2 dopamine receptors. Decreased cerebral glucose utilization (CMRglc) in the parietal and temporo-parieto-occipital region is a well-known PET finding in AD. We investigated the relationship between the Ki value and regional CMRglc (rCMRglc) with reference to cognitive impairment and wandering behavior. We studied 10 AD patients with moderately severe dementia. Using PET and the FDOPA and [18F]-fluoro-deoxyglucose techniques, the Ki value and rCMRglc in 10 regions in each hemisphere were measured. The Ki value was found to correlate with mean cortical rCMRglc. The rCMRglc of the anterior frontal, inferior frontal, and temporal lobes correlated with the Ki value; the patients with wandering behavior had lower values. Multiple regression analysis showed that the Mini-Mental State Examination score was significantly explained by the Ki value, the rCMRglc of the temporal lobe, and the rCMRglc of the parietal lobe. There is probably a functional neural network between the striatum and the frontal and temporal lobes in AD. We consider this network important, not only in cognitive impairment but also in abnormal wandering behavior.