Early-onset and late-onset Alzheimer's disease are associated with distinct patterns of memory impairment

Abstract

The goal of this study was to investigate the specific patterns of memory breakdown in patients suffering from early-onset Alzheimer's disease (EOAD) and late-onset Alzheimer's disease (LOAD). Twenty EOAD patients, twenty LOAD patients, twenty matched younger controls, and twenty matched older controls participated in this study.All participants underwent a detailed neuropsychological assessment, an MRI scan, an FDG-PET scan, and AD patients had biomarkers as supporting evidence of both amyloïdopathy and neuronal injury. Results of the neuropsychological assessment showed that both EOAD and LOAD groups were impaired in the domains of memory, executive functions, language, praxis, and visuoconstructional abilities, when compared to their respective control groups. EOAD and LOAD groups, however, showed distinct patterns of memory impairment. Even though both groups were similarly affected on measures of episodic, short term and working memory, in contrast semantic memory was significantly more impaired in LOAD than in EOAD patients. The EOAD group was not more affected than the LOAD group in any memory domain. EOAD patients, however, showed significantly poorer performance in other cognitive domains including executive functions and visuoconstructional abilities. A more detailed analysis of the pattern of semantic memory performance among patient groups revealed that the LOAD was more profoundly impaired, in tasks of both spontaneous recall and semantic recognition.Voxel-Based Morphometry (VBM) analyses showed that impaired semantic performance in patients was associated with reduced gray matter volume in the anterior temporal lobe region, while PET-FDG analyses revealed that poorer semantic performance was associated with greater hypometabolism in the left temporoparietal region, both areas reflecting key regions of the semantic network. Results of this study indicate that EOAD and LOAD patients present with distinct patterns of memory impairment, and that a genuine semantic impairment may represent one of the clinical hallmarks of LOAD.

Early-Onset Alzheimer Disease

“…EOAD, compared to LOAD, presents less commonly with memory deficits and more frequently as focal cortical or phenotypic variants (described below) 25 . Overall, EOAD patients, compared to comparably impaired LOAD patients, have better memory recognition scores and semantic memory 26 , but they tend to have worse attention, executive functions, ideomotor praxis, and visuospatial skills 25,26 . On magnetic resonance imaging (MRI), EOAD shows greater neocortical atrophy, particularly in parietal cortex, with less atrophy in the mesial temporal lobe (MTL) 27,28 .…”

Drawing Disorders in Alzheimer’s Disease and Other Forms of Dementia

“…Copying tasks are, therefore, substantially spared in degenerative diseases mainly involving the frontal (bvFTD) or temporal (SD) cortices and might be mildly impaired in the early stages of standard forms of AD, in which atrophy prevails in the medial temporal lobes, although neuroimaging studies repeatedly showed a pattern of reduced metabolism in the temporo-parietal areas [204,205]. A much more severe impairment in copying tasks is observed in early-onset AD patients and in PCA variant, in which severe constructive defects are usually associated with progressive visual-spatial disorders, including Balint syndrome and unilateral spatial neglect [100,101]. A very similar pattern of drawing impairment is found in LBD, in which visuospatial difficulties are often early and prominent and contribute to the disproportionate impairment in constructional tasks observed in these patients [151][152][153].…”

“…Some authors have, therefore, examined the relations between age at onset and drawing disorders in AD patients, and reported a high prevalence of visuoconstructional disabilities, assessed with the copy of the ROCF, in EOAD patients [101][102][103]. In some studies [102,103], but not in others [101], these drawing disorders were associated with visuospatial deficits. Furthermore, some studies [104] have shown that the presence and severity of drawing disorders certainly depends on the AD phenotype and not just on age.…”

“…The structural or functional neuroimaging abnormalities correlate with the clinical features in AD patients, because typical late-onset patients (LOAD) present with memory disorders and medial temporal lobe atrophy, whereas focal neocortical forms of AD prevail in early-onset patients (EOAD) and are associated with executive-behavioral disorders, logopenic aphasia, and (in posterior cortical atrophy) with progressive visual-spatial disorders [100,101]. Some authors have, therefore, examined the relations between age at onset and drawing disorders in AD patients, and reported a high prevalence of visuoconstructional disabilities, assessed with the copy of the ROCF, in EOAD patients [101][102][103].…”

Alzheimer’s disease with an early debut

“…У нашей пациентки симптоматика также прогрессирует достаточно быстро (за 2-3 года когнитивный дефицит достиг стадии умеренной деменции). При БАсРН, по сравнению с БА с поздним дебютом, реже встречается дефицит памяти, пациенты с БАсРН отличаются более выраженными нарушениями внимания, исполнительных функций, идеомоторного праксиса и визуально-пространственных функций [7,8]. У нашей пациентки имеющийся несомненный мнестический дефект отходит на второй план на фоне грубых нарушений праксиса, письма, счета и речи.…”