Objective: To clarify the pathological basis for Alzheimer’s disease (AD) with parkinsonism using striatal dopamine transporter (DAT) scan.

Background: Pathological basis for parkinsonism in AD is still unclear, although neuronal loss in substatia nigra has been reported in AD patients with parkinsonism.

Methods: We evaluated the function of presynaptic dopamine neuron by DAT scan in 3 cases of AD with parkinsonism.

Results: Case 1. A 73-year-old woman: Memory loss appeared 4 years before DAT scan. Only cognitive impairment was seen (revised Hasegawa dementia scale; HDS-R score was 20), when she visited our department the next year. Z score of the parahippocampal gyrus (PHG) by Voxel-Based Specific Regional Analysis System for AD (VSRAD) was 1.40. Parkinsonism, which was dominant in the left side, developed 3.5 year after the onset. DAT scan performed in the next year revealed a decreased uptake in the (predominant right) striatum. Cardiac MIBG scintigraphy was normal. REM sleep behavior disorder (RBD) and autonomic symptoms have not been seen. Case 2. A 78-year-old woman. Memory problem developed 4 years before DAT scan. The HDS-R score was 16 and the Z-score of PHG was 1.26 after two years later. She presented the right-side predominant parkinsonism 4 years later from the onset. There was no history of visual hallucinations and RBD. MIBG uptake was normal. Slightly reduced uptake was observed in the left striatum on the DAT scan. Case 3. An 86-year-old woman: She developed memory problem 7 years before DAT scan. The four years later after the onset, HDS-R score was 8 points and Z score of PHG was 3.59. Parkinsonism,which was predominant in the right side, as well as hallucinations and RBD appeared 7 years after the onset. Decreased striatum uptake was predominant in the right striatum on the DAT scan. MIBG uptake was reduced. In all patients, brain SPECT showed the reduced blood flow in the temporal lobe and the posterior cingulate gyrus.

Conclusions: Since the nerve cell loss of substantia nigra has been reported in AD patients with parkinsonism, the impairment of DAT function may be induced with the progress of AD pathology in case 1 and 2, and by concomitant Parkinson’s disease in case 3. We should consider that parkinsonism in AD patients is caused not only by the concomitant Parkinson’s disease, but also by the process of AD pathology itself.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/study-of-striatal-dopamine-transporter-function-in-alzheimers-disease-with-parkinsonism/