Real-world evaluation of Armstrong's criteria in corticobasal degeneration: Phenotypic overlap and diagnostic challenges

Background: Corticobasal degeneration (CBD) is a four-repeat tauopathy with heterogeneous clinical manifestations. Armstrong's criteria involve a two-step diagnostic approach: first, classifying patients into five clinical phenotypes—probable/possible corticobasal syndrome (CBS), frontal behavioral-spatial syndrome (FBS), non-fluent/agrammatic variant primary progressive aphasia (naPPA), and progressive supranuclear palsy syndrome (PSPS); second, determining whether they meet the clinical research criteria for probable CBD (cr-CBD) or the clinical criteria for possible CBD (p-CBD), which are distinct from the initial CBS classifications.
Objective: To investigate how real-world patients with suspected CBD fulfill Armstrong's clinical phenotypes and diagnostic criteria, and to compare clinical and imaging features between the Alzheimer's disease (AD) group and the non-AD group defined by CSF amyloid biomarkers.
Methods: We retrospectively reviewed 137 patients undergoing differential diagnosis for CBS, frontotemporal dementia, primary progressive aphasia, or PSPS. Of these, 78 met the criteria for cr-CBD (n = 36) or p-CBD (n = 42). CSF was examined in 32 patients, and based on the CSF Aβ42/40 ratio, patients were classified into an AD-group (AD-CBS; n = 6) and a non-AD group (n = 26).
Results: Among patients classified as cr-CBD or p-CBD, 79% fulfilled two or more clinical phenotypes, with FBS and PSPS most commonly. Compared with the AD group, the non-AD group showed more parkinsonian features and frontal hypoperfusion on [123I]-IMP SPECT.
Conclusion: Armstrong's criteria captured a spectrum of overlapping clinical features. While helpful in clinical phenotyping, further validation with biomarkers is essential to distinguish CBD from AD and related disorders. Prospective studies with pathological confirmation are warranted.

© 2026 Published by Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/

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