FDG-PET and SPECT studies suggest that hypometabolism and hypoperfusion in occipital lobe and posterior cingulate gyrus (PCG) are prominent features of dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), respectively. Cerebral blood flow and glucose metabolism are tightly linked to brain energy metabolism. 1H-MRS is a useful tool to directly detect energy metabolism. We aimed to use 1H-MRS to characterize metabolite concentrations in the occipital lobe and PCG in DLB and AD patients, and estimate their usefulness in the diagnosis of DLB. Nineteen DLB, 21 AD, and 18 normal control (NC) subjects underwent 1H-MRS with the voxels placed in bilateral occipital lobes and left PCG. The N-acetylaspartate (NAA) and glutamate (Glu) concentrations in occipital lobe in DLB were lower than those in AD and NC. Concentrations of these two metabolites in PCG in DLB were lower than those in NC, and were the same as those in AD. These results remained robust after correcting for relative gray matter volume in the region of interest. The NAA and Glu concentrations in occipital lobe in DLB were found correlated with global cognitive function. From the ROC curves with Glu concentrations in occipital lobe, the mean areas under the curve were 0.845 for the DLB/control (with sensitivity 83.3% and specificity 84.2%) and 0.773 for the DLB/AD (with sensitivity 66.7% and specificity 84.2%). Our study suggests that 1H-MRS investigation is valuable to detect the characteristic patterns of metabolite concentrations and is helpful in the diagnostic process and assessing dementia severity in DLB.
Keywords: Alzheimer's disease; Dementia with Lewy bodies; diagnosis; differential diagnosis; hydrogen proton magnetic resonance spectroscopy; occipital lobe; posterior cingulate gyrus.