Presynaptic dopaminergic function in early-onset Alzheimer's disease: an FP-CIT image study

• Published in: Neurobiology of aging 2020-02, Vol.86, p.75-80
• Main Authors: Jang, Hyemin, Jang, Young Kyoung, Park, Seongbeom, Kim, Si Eun, Kim, Seung Joo, Cho, Soo Hyun, Youn, Jinyoung, Seo, Sang Won, Kim, Hee Jin, Na, Duk L.
• Format: Article
• Language: English
• Subjects: Alzheimer's disease; Amyloid PET; FP-CIT PET; Parkinson's disease/parkinsonism; PET
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2019.10.007

We aimed to investigate whether amyloid-β (Aβ) positive early-onset Alzheimer's disease (EOAD) patients have presynaptic dopaminergic deficits on in vivo 18F-FP-CIT PET imaging. We enrolled 34 EOAD patients and 9 cognitively normal controls (NC), all of whom underwent 18F-florbetaben and 18F-FP-CIT PET at Samsung Medical Center. We assessed motor symptoms using Unified Parkinson's Disease Rating Scale (UPDRS) and divided the EOAD patients into 2 groups using a UPDRS cutoff of 10. We compared regional florbetaben and FP-CIT uptake across the NC and the 2 EOAD groups with lower and higher UPDRS and investigated the associations between regional florbetaben or FP-CIT uptake and UPDRS in EOAD patients. Among the 30 EOAD patients who were Aβ positive on florbetaben PET, the higher UPDRS (>10) group (n = 9) had a longer disease duration (7.2 ± 3.3 vs. 4.1 ± 1.8, p = 0.002), and had a tendency to have lower Mini-Mental State Examination (9.6 ± 7.9 vs. 15.0 ± 6.0, p = 0.052) than the lower UPDRS (≤10) group (n = 21). Across the NC and the 2 EOAD groups, there were no significant differences in FP-CIT uptake in caudate (p = 0.122) and putamen (p = 0.685) or florbetaben uptake in midbrain (p = 0.890). Finally, regression analyses showed that UPDRS was not associated with FP-CIT uptake in caudate (p = 0.913) or putamen (p = 0.407), or with florbetaben PET uptake in caudate (p = 0.553), putamen (p = 0.617), midbrain (p = 0.843), or global cortex (p = 0.658). This study showed that parkinsonian signs in EOAD patients may be related with mechanisms other than presynaptic dopaminergic deficit. Our finding is clinically important because it suggests that L-dopa treatment in EOAD with parkinsonian signs may not improve motor symptoms. •Many of early-onset Alzheimer's disease (EOAD) patients have parkinsonism.•Aβ+ EOAD patients have normal presynaptic dopamine transporter (DAT) binding.•DAT or Aβ PET binding was not related with severity of parkinsonism in EOAD.•Parkinsonism in EOAD might not be attributed to presynaptic dopaminergic deficit.