Brainstem and cortical Lewy bodies in patients presenting clinically with Alzheimer's disease

Alzheimer disease pathology in subjects without dementia in 2 studies of aging: the Nun Study and the Adult Changes in Thought Study

Individuals with antemortem preservation of cognition who show autopsy evidence of at least moderate Alzheimer disease (AD) pathology suggest the possibility of brain reserve, that is, functional resistance to structural brain damage. This reserve would, however, only be relevant if the pathologic markers correlate well with dementia. Using data from the Nun Study (n = 498) and the Adult Changes in Thought (ACT) Study (n = 323), we show that Braak staging correlates strongly with dementia status. Moreover, participants with severe(Braak stage V-VI) AD pathology who remained not demented represent only 12% (Nun Study) and 8% (ACT study) of nondemented subjects. Comparison of these subjects to those who were demented revealed that the former group was often significantly memory-impaired despite not being classified as demented. Most of these nondemented participants showed only stage V neurofibrillary pathology and frontal tangle counts that were slightly lower than a comparable (Braak stage V) dementia group. In summary, these data indicate that, in individuals with AD-type pathology who do not meet criteria for dementia, neocortical neurofibrillary tangles are somewhat reduced and incipient cognitive decline is present. Our data provide a foundation for helping to define additional factors that may impair, or be protective of, cognition in older adults.

Differences in olfactory and visual memory in patients with pathologically confirmed Alzheimer's disease and the Lewy body variant of Alzheimer's disease

Recognition and remote memory for odors, faces, and symbols were assessed in patients with pathologically confirmed Lewy body variant of Alzheimer's disease (LBV), patients with pathologically confirmed Alzheimer's disease (AD), and healthy elderly controls. On recognition memory tasks, LBV and AD patients showed significantly lower discriminability (d') than controls, particularly for olfactory stimuli. However no significant differences were found in the bias measure (c). When participants rated familiarity (a proposed measure of remote memory) of olfactory stimuli LBV and AD patients reported significantly lower familiarity than controls. Familiarity ratings were significantly lower in LBV patients than in AD patients for olfactory, but not for visual stimuli. Consistent with prior reports, the LBV patients showed significantly poorer odor thresholds than AD patients. The results suggest that recognition memory for olfactory stimuli is impaired in LBV and AD. However, patients with LBV are more impaired than patients with AD on tasks requiring remote memory for olfactory but not visual stimuli. The findings suggest that odor memory tasks may be useful in the assessment of LBV and AD.

Metabolic impairment of brain metabolism in patients with Lewy body dementia

A reliable assessment of dementia is essential for a differentiated treatment. Recent studies have demonstrated a poor accuracy of clinical criteria for diagnosis of Lewy body dementia. Diffuse Lewy body disease (LBD) is the second most common cause of senile degenerative dementia and is characterized histologically by the occurrence of Lewy bodies in allocortical, neocortical and subcortical structures. Seven male patients (mean age 81 years) with clinically suspected diffuse LBD were investigated with 18F-fluorodeoxyglucose (FDG)-PET using a Siemens ECAT-ART PET-scanner. The 18F-FDG-PET showed a diffuse glucose hypometabolism in the entire cerebral cortex with relative sparing of the primary sensory-motor cortex in all patients. This diffuse metabolic impairment in the entire cortex with relative sparing of central region seems to be a typical pattern for LBD, distinct from Alzheimer's disease.

Brain banking for neurodegenerative diseases

PURPOSE OF REVIEW

Brain banking remains a necessity for the study of neurodegenerative diseases. While the characterization of pathology observed at autopsy confirms clinical diagnosis, the structure and contents of pathological hallmarks are the starting point from which disease pathogenesis may be elucidated. Traditional neuropathology has served to define, characterize, and diagnose neurodegenerative diseases, accompanied by clinical presentation. The pathological substrates are then studied for their role in how they cause dysfunction in disease, or how their accumulation is presumably damaging.

RECENT FINDINGS

New genetic findings have revolutionized these studies and have prompted a reexamination of traditional pathological definitions of disease. Many familial genetic mutations have been found, encoding proteins such as synuclein, parkin, tau, and others, creating genetic ways to define neurodegenerative diseases. Many of these proteins are components of aggregates, thus the ability to label these proteins has revealed new pathological characteristics that must be standardized. More complicating is that many proteins genetically linked to clinically distinct diseases are involved in overlapping neuropathology of what now appears to be a spectrum of diseases: 'synucleinopathies', 'tauopathies', and so on. Moreover, as genetic discoveries fuel molecular experiments on brain tissue, banking methods must now accommodate these techniques. Lastly, DNA screening involves ethical issues beyond those which were previously considered with postmortem tissue banking.

SUMMARY

As more proteins are linked to disease, more is revealed about the underlying causative mechanisms, exposing points for interventions. To achieve this end, characterization for neurodegenerative disease in the post genomic era must include genotype, phenotype and clinical characterization, and postmortem brain banking data which includes these.