Abstract
A significant portion of patients with early-onset Alzheimer's disease (age of onset <65 years) have non-amnestic presentations, such as logopenic primary progressive aphasia (lvPPA), posterior cortical atrophy (PCA), and the behavioral/executive variant. The NIA-AA criteria for probable AD recognize language, visuospatial, and executive variants but do not specify other presentations for AD. We reviewed 220 patients with clinically diagnosed early-onset AD by NIA-AA criteria from a subspecialty university clinic. All patients had biomarker-supported clinically probably AD either by fluorodeoxyglucose positron emission tomography (FDG-PET) or cerebrospinal fluid β-amyloid or tau biomarkers. The presenting symptoms and clinical and neuroimaging characteristics were reviewed. We identified 15 (6M/9F) right-handed patients with AD who presented with predominant non-aphasic, non-visuospatial symptoms referable to the left parietal lobe. All lacked family history for an autosomal dominant disorder. Their ages of presentation and onset were 57.82 (8.9) and 55.11 (5.51), respectively. Mini-Mental State at onset was 23.1 (3.67) with retrospective Clinical Dementia Rating Scores of 1.23 (0.53). The predominant presenting symptoms were decreased writing (lexical and transitional motor) (9) decreased manual dexterity (3), and acalculia (5). On examination, the agraphia was usually lexical plus transitional motor; 12 had limb apraxia (10 ideomotor and 6 limb-kinetic); the acalculia was an anarithmetia; and 3 had the full Gerstmann syndrome. Neuroimaging, including FDG-PET was consistent with prominent dysfunction of the left parietal lobe. Patients with early-onset AD may present with variants such as lvPPA and PCA, and it is now possible to diagnose them with clinical AD using NIA-AA criteria. However, other variant presentations of early-onset AD need to be considered, including the combination of symptoms referable to disproportionate involvement of the left parietal lobe.
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