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Nobuto SHIBATA1), Yosuke ICHIMIYA1), Heii ARAI3)3)Alzclinic Tokyo, Tokyo, Japan2)Department of Neuropsychiatry, St. Marianna University School of Medicine, Kanagawa, Japan1)Department of Psychiatry and Behavioral Science, Juntendo University Graduate School of Medicine, Tokyo, JapanMoto NISHIGUCHI1), Toshiki TAKAYAMA1), Koji KASANUKI2), Tsuneyoshi OTA1), Introduction: Early-onset dementia is fast-progressing compared with late-onset dementia, with major clinical characteristics including prominent focal cerebral symptoms. Given its economic and psychological implications, proper diagnosis and treatment at an early stage is essential. In the present study, the authors conducted a retrospective study to evaluate the usefulness of various numerical indices (including CIScore calculated by eZIS, cerebral blood flow SPECT analysis software) in the differential diagnosis of early-onset dementia.Materials and Methods: This study involved patients with early-onset and mild dementia who were receiving ambulatory care at our outpatient department specializing in Alzheimer’s disease (14 MCI patients, 16 AD patients, and 16 probable/possible DLB patients). ROC analysis was performed for each SVA numerical index calculated by eZIS to calculate AUC. For the AD and DLB groups, correlation between the CIScore and MMSE was assessed.Results: When SVA-A (severity) was used to differentiate AD from MCI and DLB from MCI, the respective AUC values were 0.960 and 0.911. When CIScore was used to differentiate AD from DLB (threshold value: 0.225), the obtained AUC value was 0.941, and the accuracy, sensitivity, and specificity were 90.6%, 87.5%, and 93.7%, respectively. No significant correlation was observed between the MMSE and CIScore scores in these disease groups.Conclusion: The results of this study have suggested that the SVA-A is a useful index for evaluating the conversion from MCI to either early-onset AD or DLB, and that the CIScore is useful for differentiating AD from DLB in both late-onset and early-onset dementia cases.Key words: early-onset dementia, early diagnosis, differential diagnosis, SPECTCorresponding author: Nobuto Shibata Department of Psychiatry and Behavioral Science, Juntendo University Graduate School of Medicine2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, JapanTEL: +81-3-5802-1071　FAX: +81-3-5802-1071　E-mail: nshibata@juntendo.ac.jp〔Received　Apr. 30, 2022〕〔Accepted　Jul. 8, 2022〕J-STAGE Advance published date: Sep. 9, 2022Copyright © 2022 The Juntendo Medical Society. This is an open access article distributed under the terms of Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original source is properly credited. doi: 10.14789/jmj.JMJ22-0018-OAJuntendo Medical Journal2022. 68(5), 505-512Original ArticlesThe Cingulate Island Sign is Useful for a Differential Diagnosis of Early-Onset Alzheimer's Disease and Dementia with Lewy Bodies: A 99mTc-ECD SPECT StudyIntroductionEarly-onset dementia is a term used to describe any form of dementia that develops in people aged 64 or below. Epidemiological research estimates that approximately 40 thousand people have this condi-tion in Japan. The most common cause is vascular dementia (VD), which is followed by Alzheimer’s disease (AD), head trauma, and dementia with Lewy bodies (DLB)1). Compared with late-onset dementia, early-onset dementia is fast-progressing and clinically characterized by prominent focal cerebral symptoms. Given its economic and psycho-logical implications, proper diagnosis and treatment at an early stage is essential.Neuropsychological tests, such as Mini-Mental State Examination (MMSE)2), are the primary means of diagnosing dementia. However, recent 505