Abstract
The cingulate island sign (CIS) refers to the relative sparing of metabolism in the posterior cingulate cortex (PCC) and represents an important biomarker in distinguishing dementia with Lewy bodies (DLB) from Alzheimer disease (AD). The underlying basis of the CIS is unknown; therefore, our aim was to investigate which neurodegenerative changes underpin the formation of CIS. Using quantitative neuropathology, α-synuclein, phosphorylated Tau, and amyloid-β pathology was assessed in 12 DLB, 9 AD and 6 age-matched control patients in the anterior cingulate (ACC), midcingulate, PCC, precuneus/cuneus and parahippocampal gyrus. All participants had undergone 99mTc-hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography imaging during life to define the presence or absence of CIS. In the DLB group, no significant correlations were observed between CIS ratios and neurodegenerative pathology in PCC. In DLB, however, the ACC showed lower HMPAO uptake, as well as significantly higher α-synuclein and amyloid-β burden compared with PCC, possibly underlying the relative preservation of perfusion in PCC when compared with ACC. Our findings suggest that neurodegenerative pathology does not directly correlate with the CIS in DLB, and other metabolic or pathological changes are therefore more likely to be relevant for the development of the CIS.
Highlights
Dementia with Lewy bodies (DLB) is second only to Alzheimer disease (AD) in terms of prevalence, accounting for $15%–20% of all neuropathologically defined dementia patients [1]
Alpha-synuclein pathology was significantly higher in dementia with Lewy bodies (DLB) patients compared with controls and AD in anterior cingulate cortex (ACC), midcingulate cortex (MCC), posterior cingulate cortex (PCC), precuneus and cuneus (Pr/Cu), and parahippocampal gyrus (PHG) (p < 0.001; Fig. 2A)
In this study we observed significantly higher cingulate island sign (CIS) ratios in DLB compared with AD using 99mTc-hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT), in line with previous FDG-positron-emission tomography (PET) studies [9, 12]
Summary
Dementia with Lewy bodies (DLB) is second only to Alzheimer disease (AD) in terms of prevalence, accounting for $15%–20% of all neuropathologically defined dementia patients [1]. The cingulate island sign (CIS) is a supportive biomarker in discriminating DLB from AD according to diagnostic criteria [2, 8, 9], and refers to the relative preservation of posterior cingulate cortex (PCC) metabolism, in relation to precuneus and cuneus (Pr/Cu) metabolism, and is commonly observed in DLB patients [10, 11] This can be identified using 18F-fluorodeoxyglucose (FDG) positron-emission tomography (PET) imaging and using hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT) as a marker of perfusion to define the CIS [12]. Clinico-pathological correlation has VC 2019 American Association of Neuropathologists, Inc
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