The neuropsychology of preclinical Alzheimer's disease and mild cognitive impairment

Subjects in the preclinical stages of Alzheimer's disease (AD) typically record neuropsychological performance between that of healthy older individuals and demented patients. More specifically, deficits on measures of verbal episodic memory are commonly reported in these patients, while other cognitive functions (e.g. language, praxis and executive function) seem to be spared. A similar neuropsychological profile is observed in elderly subjects with mild cognitive impairment (MCI), a disorder that is attracting increasing research interest. Evidence from lesion and functional imaging studies, as well as volumetric imaging in probable AD and MCI patients, suggests that the cognitive deficits observed in these disorders may be related to medial temporal lobe dysfunction. An issue currently under investigation is whether MCI represents the preclinical stages of AD or a distinct and static cognitive aetiology. In an attempt to address this issue, present investigations are adopting a convergent approach to the detection of preclinical AD, where multiple risk factors are considered when making a diagnosis.     

Mild cognitive impairment: a cross-national comparison

OBJECTIVE: The main aim of this collaborative study was to assess the comparability of the most commonly used criteria for mild cognitive impairment (MCI) by comparing the cognitive performance of patients with MCI from the Mayo Clinic (USA) and the Karolinska Institutet (Sweden). METHODS: Standardised neuropsychological test scores were used to compare the two samples from the two institutions with regard to the number of cognitive domains in which performance was below 1.5 SD. Possible predictors for the conversion from MCI to Alzheimer's disease (AD) were assessed. RESULTS: When the two institutions were considered together in the Cox proportional hazard model, the number of affected cognitive domains below 1.5 SD was a significant predictor of time to AD diagnosis with age, education, and APOE epsilon4 genotype entered into the same model as covariates. The number of affected cognitive areas remained as a significant predictor when the institutions were considered separately. The logistic regression model of conversion to AD showed that only tests assessing learning and retention were predictors of developing AD. CONCLUSIONS: Differences in population as well as in methodology of case ascertainment as well as other aspects may account for the observed variability between samples of patients with MCI. The number of impaired cognitive factors at baseline can predict the progression from MCI to AD. Furthermore, tests assessing learning and retention are the best predictors for progression to AD.     

Hippocampal morphology and autobiographic memory in mild cognitive impairment and Alzheimer's disease

Autobiographical memory (AM) comprises memories of one's own past that are characterized by a sense of subjective time and autonoetic awareness. AM deficits are among the major complaints of patients with Alzheimer's disease (AD) even in early or preclinical stages. However, little is known on the association between cerebral alterations and AM in mild cognitive impairment (MCI) and AD. In the current study, patients with AD or MCI and healthy controls underwent high-resolution magnetic resonance imaging (MRI) and neuropsychological testing including semi-structured assessment of semantic and episodic AM of distinct lifetime periods. In MRI analysis, FSL-FIRST was used to automatically ascertain volume and shape of the hippocampal formation. Episodic, but not semantic AM loss was associated with morphological changes of the hippocampus, primarily involving the left hemisphere. According to shape analyses, these associations referred to regionally specific rather than global atrophy of the hippocampus. Our study demonstrates that loss of episodic AM early in the course of AD is associated with regionally confined hippocampal atrophy, thus supporting the multiple trace theory for the role of the hippocampus in episodic AM. Our findings are not only relevant for the understanding of memory function, but may also contribute to facilitating the early diagnosis of AD.     

Efficacy of cognitive rehabilitation in patients with mild cognitive impairment treated with cholinesterase inhibitors

BACKGROUND: Individuals who have Mild Cognitive Impairment (MCI) may be in a transitional stage between aging and Alzheimer's disease (AD). The high rate of conversion from MCI to AD makes early treatment an important clinical issue. Recent evidence suggests that cognitive training intervention may reduce the rate of progression to AD. OBJECTIVES: To evaluate the efficacy of a NeuroPsychological Training (TNP) in patients with MCI who are treated with cholinesterase inhibitors (ChEIs), compared with patients MCI treated only with ChEIs and patients not treated, in a longitudinal, one year follow-up study. METHODS: One year longitudinal and retrospective comparison study of neuropsychological performances in 59 subjects affected by Mild Cognitive Impairment (MCI) according to Petersen's criteria. Fifteen subjects were randomised to receive TNP plus cholinesterase inhibitors; 22 subjects cholinesterase inhibitors alone and 22 subjects no treatment. All the subjects referring memory complaints, corroborated by an informant, underwent a multidimensional assessment concerning neuropsychological, behavioural and functional characteristics, at baseline and after one year follow-up. RESULTS: Subjects without treatment maintained their cognitive, functional and behavioural status after one year; patients treated only with ChEIs improved in depressive symptoms whereas subjects treated with TNP and ChEIs showed significant improvements in different cognitive areas, such as memory, abstract reasoning and in behavioural disturbances, particularly depressive symptoms. CONCLUSIONS: A long-term TNP in ChEIs-treated MCI subjects induces additional cognitive and mood benefits.     

In vivo parahippocampal white matter pathology as a biomarker of disease progression to Alzheimer's disease

Noninvasive diagnostic tests for Alzheimer's disease (AD) are limited. Postmortem diagnosis is based on density and distribution of neurofibrillary tangles (NFTs) and amyloid‐rich neuritic plaques. In preclinical stages of AD, the cells of origin for the perforant pathway within the entorhinal cortex are among the first to display NFTs, indicating its compromise in early stages of AD. We used diffusion tensor imaging (DTI) to assess the integrity of the parahippocampal white matter in mild cognitive impairment (MCI) and AD, as a first step in developing a noninvasive tool for early diagnosis. Subjects with AD (N = 9), MCI (N = 8), or no cognitive impairment (NCI; N = 20) underwent DTI‐MRI. Fractional anisotropy (FA) and mean (MD) and radial (RD) diffusivity measured from the parahippocampal white matter in AD and NCI subjects differed greatly. Discriminant analysis in the MCI cases assigned statistical membership of 38% of MCI subjects to the AD group. Preliminary data 1 year later showed that all MCI cases assigned to the AD group either met the diagnostic criteria for probable AD or showed significant cognitive decline. Voxelwise analysis in the parahippocampal white matter revealed a progressive change in the DTI patterns in MCI and AD subjects: whereas converted MCI cases showed structural changes restricted to the anterior portions of this region, in AD the pathology was generalized along the entire anterior–posterior axis. The use of DTI for in vivo assessment of the parahippocampal white matter may be useful for identifying individuals with MCI at highest risk for conversion to AD and for assessing disease progression. J. Comp. Neurol. 521:4300–4317, 2013. © 2013 Wiley Periodicals, Inc.     

Strukturelle zerebrale Veränderungen bei Probanden mit leichter kognitiver Beeinträchtigung Eine MR-volumetrische Studie

The aim of the present study was to investigate the morphological changes in subjects with mild cognitive impairment (MCI) revealed by quantitative magnetic resonance imaging (MRI). Twenty-one subjects with cognitive impairment and 22 healthy controls were compared with 12 patients suffering from mild Alzheimer's disease (AD). The volumes of the following brain structures were assessed: total intracranial compartment, cerebrospinal fluid compartment, whole brain, and medial temporal substructures (hippocampus and parahippocampal gyrus). Subjects with mild cognitive impairment showed a significantly reduced volume of the right parahippocampal gyrus over healthy controls. Volumes of the other regions and structures did not differ between the MCI group and controls. The volumetric and neuropsychological findings of the present study support the hypothesis that mild cognitive impairment - at least in some of the affected individuals - can be seen as a preclinical stage of AD and that atrophy of the parahippocampal gyrus might be useful as an early marker of AD.     

The fornix and mammillary bodies in older adults with Alzheimer's disease, mild cognitive impairment, and cognitive complaints: a volumetric MRI study

The fornix and mammillary bodies are important limbic structures that have not been systematically investigated in the earliest stages of preclinical dementia. The present study examined volumetric changes in the fornix and mammillary bodies and improved previously established tracing guidelines to increase reliability and provide more comprehensive measurements. Volumetric measurements were made in euthymic older adults, including 16 patients with mild Alzheimer's disease (AD), 20 patients with amnestic mild cognitive impairment (MCI), 20 individuals with cognitive complaints (CC) but normal neuropsychological test performance, and 20 demographically matched healthy controls (HC). Structural magnetic resonance imaging included a T1-weighted 1.5-mm coronal volume, acquired on a GE 1.5T LX scanner. After adjustment for total intracranial volume (ICV), significant volume reductions were observed in the fornix and mammillary bodies in patients with AD as compared with HC, CC, and MCI participants. No volume differences were seen between the HC, CC, and MCI groups. Study findings are consistent with previous research showing volume decreases of the fornix and mammillary bodies in AD, and provide new data on the relative preservation of these structures in preclinical disease stages. Results suggest that atrophy of the fornix and mammillary bodies becomes apparent at the point of conversion from MCI to AD. Longitudinal assessments are needed to delineate the time course and extent of the observed volumetric changes.     

Neuropsychological markers of progression from mild cognitive impairment to Alzheimer's disease

To find early clinical markers that may predict a likely progression to Alzheimer's disease (AD), the authors performed neuropsychological tests on 82 mild cognitive impairment (MCI) subjects. After 3 years, 38 patients developed AD while 44 retained the diagnosis of MCI. The cognitive differences between the groups were studied. Patients who developed AD showed significantly lower values than did MCI subjects in some neuropsychological scores (P = .02-.001), with sensitivities and specificities higher than 84% and 64%, respectively, for detecting early-onset AD, with a 7.9-fold increased risk of converting to AD (P < .001). Regarding the logistic regression model, the CAMCOG Memory and Perception cognitive screening items were the optimum independent tools to classify the patients who will progress to AD, showing a relative risk of progression of 10.5 (P = .002), 5.5 (P = .008), and 3.9 times (P = .05), respectively, with a sensibility of of 92.1% and a specificity 72.7%.     

A decade of pre-diagnostic assessment in a case of familial Alzheimer's disease: tracking progression from asymptomatic to MCI and dementia

Detailed study of the very earliest phases of Alzheimer's disease (AD) is seldom possible, especially those changes preceding the development of mild cognitive impairment (MCI), which may occur years before diagnosis. Knowledge of imaging and neuropsychological features of these early stages would add insight into this poorly understood phase of the disease. We present data from a subject who entered a longitudinal study of individuals at risk of familial Alzheimer's disease (FAD), as a healthy volunteer with no memory complaints, undergoing 12 assessments between 1992 and 2003. Longitudinal MRI, neuropsychological and clinical data are presented over the decade preceding this man's diagnosis, through the asymptomatic and prodromal preludes to his presentation with MCI and on to eventual conversion to AD.     

A decade of pre-diagnostic assessment in a case of familial Alzheimer’s disease: tracking progression from asymptomatic to MCI and dementia

Detailed study of the very earliest phases of Alzheimer’s disease (AD) is seldom possible, especially those changes preceding the development of mild cognitive impairment (MCI), which may occur years before diagnosis. Knowledge of imaging and neuropsychological features of these early stages would add insight into this poorly understood phase of the disease. We present data from a subject who entered a longitudinal study of individuals at risk of familial Alzheimer’s disease (FAD), as a healthy volunteer with no memory complaints, undergoing 12 assessments between 1992 and 2003. Longitudinal MRI, neuropsychological and clinical data are presented over the decade preceding this man’s diagnosis, through the asymptomatic and prodromal preludes to his presentation with MCI and on to eventual conversion to AD.     

Conversion from preclinical to dinical stage of Alzheimer's disease as shown by decline of cognitive function in carriers of the Swedish APP-mutation

The characterisation of the borderline syndrome between normal cognitive function and Alzheimer's disease (AD), often mentioned as Mild Cognitive Impairment (MCI) has been a goal for recent research. However, a variety of definitions of MCI-like syndromes and the uncertainty about the final diagnosis have hampered progress. To overcome these problems, the present study will describe cognitive function in two healthy mutation carriers and two matched non-carriers of the Swedish double mutation family, during the time period when carriers convert to a symptomatic stage, i.e., true preclinical AD, and finally into the stage when a clinical diagnosis of AD is first possible. The findings question the generality of common MCI concepts and the commonly held beliefs about cognitive features in late preclinical stage of AD.     

Disturbed sleep patterns in elders with mild cognitive impairment: the role of memory decline and ApoE ɛ4 genotype

Sleep disturbances are prevalent in patients with Alzheimer' disease (AD), being one of the most troubling symptoms during the progression of disease. However, little research has been made to determine if impaired sleep patterns appear years before AD diagnosis. This study tries to shed light on this issue by performing polysomnographic recordings in healthy elders and patients with mild cognitive impairment (MCI). We further investigated whether changes in sleep patterns parallel memory decline as well as its relationship with the Apolipoprotein E (ApoE) ?4 genotype. Results showed a significant shortening of rapid eye movement (REM) sleep together with increased fragmentations of slow-wave sleep in MCI patients relative to healthy elders. Interestingly, we further showed that reduction of REM sleep in MCI patients with ApoE ?4 was more noticeable than in ?4 non-carriers. Contrary to our initial hypothesis, changes in sleep patterns were not correlated with memory performance in MCI patients. Instead, increased REM sleep accompanied enhanced immediate recall in MCI ?4 non-carriers. Taken together, these results suggest that sleep disruptions are evident years before diagnosis of AD, which may have implications for early detection of dementia and/or therapeutic management of sleep complaints in MCI patients.     

The role of event-related potentials in cognitive decline in Alzheimer’s disease

ObjectivesEarly diagnosis and monitoring of disease progression have become vital in clinical practice as disease modifying treatments for Alzheimer’s disease (AD) become available. This one-year prospective study aimed to clarify the usefulness of event-related potentials (ERPs) in cognitive decline and elucidate their cognitive significance in AD.MethodsUsing the Cognitive Abilities Screening Instrument (CASI) and ERPs, probable AD patients, mild cognitive impairment (MCI) patients, and normal controls were recruited.ResultsThe AD and MCI patients had significantly decreased cognitive function and manifested a delay of P300 latency. The P300 latencies demonstrated significantly more prolongation than their baseline values in probable AD and MCI patients, although their CASI scores showed no statistically significant decline. Whereas N100, P200, and N200 components did not reach statistical differences between groups either in the baseline or follow-up assessments and did not show significant change on follow-up.ConclusionThe combination of neuropsychological tests and P300 measurements proved useful in improving reliability and increasing sensitivity to early cognitive decline or disease progression in AD patients.SignificanceThe P300 latency may reflect cognitive decline more sensitively than neuropsychological tests in the longitudinal follow-up of AD patients.     

Early symptoms and signs of cognitive deficits might not always be detectable in persons who develop Alzheimer's disease

OBJECTIVE:Clinical syndromes such as amnestic mild cognitive impairment (MCI) are highly predictive of future development of Alzheimer's disease (AD), but it is not known how many of the individuals that develop the disease can be identified with these syndromes. This study aims to determine how many individuals with AD show detectable symptoms or clinical signs of cognitive deficits three years before diagnosis.METHODS: 152 incident AD cases were identified in a dementia-free cohort of 1417 persons aged 75-95, after three-year follow-up from a prospective population-based study, the Kungsholmen Project. Symptoms of cognitive impairment including the subjective report of memory problems, and cognitive deficits were objectively measured with an extensive neuropsychological test battery at baseline. Incident AD was clinically diagnosed according to DSM-IIIR criteria at three-year follow-up.RESULTS: Only half of future AD cases reported subjective memory problems three years before diagnosis. More than one-third of incident AD cases did not exhibit detectable deficits in any of the investigated specific cognitive domains. Only 38.3% had both subjective complaints and domain-specific cognitive deficits.CONCLUSIONS: Symptoms and signs currently used to define MCI are not always present in persons who develop AD. Increasing the number of potentially identifiable and treatable preclinical AD cases is unfeasible unless more sensitive subjective and objective markers are identified. Furthermore, as only half of future AD cases report subjective memory problems three years before diagnosis, the number of persons coming to the attention of medical care is limited.     

Assessing Visuoconstructional Performance in AD,MCI and Normal Elderly Using the Beery Visual-Motor Integration Test

This study evaluated the Beery Visual-Motor Integration Test (VMI) as a measure of construction ability in Alzheimer’s disease (AD) and mild cognitive impairment (MCI). Construction deficits are an early sign of Alzheimer’s disease. Commonly used tests of construction abilities are complex, often intimidating to impaired elders, and lack a range of items. The VMI has items ranging from very easy to difficult, allowing even impaired patients to enter task set, and elderly norms are available. It has not yet been validated for use in diagnosis of AD or MCI. Two patients groups (n =43 MCI and 40 AD) recruited from a memory clinic and a non-demented control group (n =43) recruited from the community were administered a battery of neuropsychological measures including the VMI. Results revealed that the VMI is useful for discriminating AD from MCI. Qualitative errors produced on the VMI provide additional information beyond the standard score about the patient’s cognitive status.     

Antioxidants for the treatment of mild cognitive impairment

The isolated deficit in recent memory frequently associated with decline to Alzheimer's disease (AD) is defined as mild cognitive impairment (MCI). The observed progression of MCI to AD suggests a common pathogenesis between these two clinical syndromes, and several neuroimaging, neuropsychological and biological methods are applied with the purpose of identifying subjects at risk of AD. Among these methods, the evaluation of a condition of oxidative stress is gaining increasing attention. Since oxidative stress seems to be involved in the earliest phases of AD, and MCI may be considered as a prodromal phase of dementia, it is an attractive issue to focus therapeutic interventions on the early phase of the disease.     

Assessing visuoconstructional performance in AD, MCI and normal elderly using the Beery Visual-Motor Integration Test

This study evaluated the Beery Visual-Motor Integration Test (VMI) as a measure of construction ability in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Construction deficits are an early sign of Alzheimer's disease. Commonly used tests of construction abilities are complex, often intimidating to impaired elders, and lack a range of items. The VMI has items ranging from very easy to difficult, allowing even impaired patients to enter task set, and elderly norms are available. It has not yet been validated for use in diagnosis of AD or MCI. Two patients groups (n = 43 MCI and 40 AD) recruited from a memory clinic and a non-demented control group (n = 43) recruited from the community were administered a battery of neuropsychological measures including the VMI. Results revealed that the VMI is useful for discriminating AD from MCI. Qualitative errors produced on the VMI provide additional information beyond the standard score about the patient's cognitive status.     

Plasma level of chitinase 3-like 1 protein increases in patients with early Alzheimer’s disease

Previously, chitinase 3-like 1 (CHI3L1) protein level was increased in various inflammatory conditions and cancers. This study was aimed to evaluate the plasma CHI3L1 level as a potential prognostic biomarker for Alzheimer’s disease (AD). Forty-nine patients with mild cognitive impairment (MCI), 61 patients with mild to severe AD, and 35 healthy elderly controls were recruited for this study. They were given a comprehensive neuropsychological test battery including a mini-mental status examination (MMSE), clinical dementia rating (CDR), and neuropsychiatric inventory (NPI). The CHI3L1 levels were measured using a specific enzyme-linked immunosorbent assay in the plasma and cerebrospinal fluid (CSF). A significant increase in the mean plasma level of CHI3L1 was found in early AD patients compared to control subjects and MCI patients. No significant difference was found between MCI patients and controls. There was a significant positive correlation between CHI3L1 levels and neuropsychological test scores such as CDR and NPI in MCI and early AD patients. Our results demonstrate that CHI3L1 plasma levels are elevated in early AD compared to control or MCI patients. Thus, CHI3L1 plasma levels may be useful as a biomarker, reflecting disease severity in AD patients.     

Using artificial neural networks in clinical neuropsychology: high performance in mild cognitive impairment and Alzheimer's disease

Mild cognitive impairment (MCI) is a transitional state between normal aging and Alzheimer disease (AD). Artificial neural networks (ANNs) are computational tools that can provide valuable support to clinical decision making, classification, and prediction of cognitive functioning. The aims of this study were to develop, train, and explore and develop the ability of ANNs to differentiate MCI and AD, and to study the relevant variables in MCI and AD diagnosis. The sample consisted of 346 controls and 79 MCI and 97 AD patients. A linear discriminant analysis (LDA) and ANNs with 12 input neurons (10 subtests of a neuropsychological test, the abbreviated Barcelona Test; age; and education), 4 hidden neurons, and output neuron (diagnosis) were used to classify the patients. The ANNs were superior to LDA in its ability to classify correctly patients (100-98.33% vs. 96.4-80%, respectively) and showed better predictive performance. Semantic fluency, working and episodic memory and education showed up as the most significant and sensitive variables for classification. Our results indicate that ANNs have an excellent capacity to discriminate MCI and AD patients from healthy controls. These findings provide evidence that ANNs can be a useful tool for the analysis of neuropsychological profiles related to clinical syndromes.     

The new 2011 recommendations of the National Institute on Aging and the Alzheimer's Association on diagnostic guidelines for Alzheimer's disease: Preclinal stages, mild cognitive impairment, and dementia

BackgroundCriteria for the clinical diagnosis of Alzheimer's disease (AD) were established in 1984, and they needed to be updated and revised, in vue of the scientific knowledge acquired over the last decades.MethodsThe National Institute on Aging (NIA) and the Alzheimer's Association (AA) sponsored a series of advisory round table meetings to establish a revision of diagnostic and research criteria for AD. The workgroups reviewed the biomarker, epidemiological, and neuropsychological evidence, and proposed conceptual frameworks as well as operational research criteria based on the prevailing scientific evidence to date.ResultsThree preclinical stages of AD were proposed: asymptomatic amyloidosis, asymptomatic amyloidosis + neurodegeneration, amyloidosis + neurodegeneration + subtle cognitive decline. The preclinical workgroup developed recommendations to determine the factors, which best predict the risk of progression from normal cognition to mild cognitive impairment (MCI) and AD dementia. It is necessary to refine these models with longitudinal clinical research studies. The workgroups on MCI and AD dementia sought to ensure that the revised criteria would be flexible enough to be used by both general healthcare providers without access to neuropsychological testing, advanced imaging, and cerebrospinal fluid measures, and specialized investigators involved in research or in clinical trial studies who would have these tools available. The symptomatic predementia phase of AD was referred to as MCI due to AD. Core clinical and cognitive criteria of MCI were proposed, the final set of criteria for MCI due to AD has four levels of certainty, depending on the presence and nature of the biomarker findings. Criteria for all-cause dementia and for AD dementia were presented. Dementia caused by AD were classified in: probable AD dementia, possible AD dementia, and probable or possible AD dementia with evidence of the AD pathophysiological process, for use in research settings. The core clinical criteria for AD dementia will continue to be the cornerstone of the diagnosis in clinical practice, but biomarker evidence is expected to enhance the pathophysiological specificity of the diagnosis.ConclusionsIn the revised criteria, a conceptual distinction is made between AD pathophysiological processes and clinically observable syndromes. The core clinical criteria of the recommendations regarding MCI due to AD and AD dementia are intended to guide diagnosis in the clinical setting whereas the recommendations of the preclinical AD workgroup are intended purely for research purposes and do not have any clinical implications. Considerable work is needed to validate the criteria that use biomarkers and to standardize biomarker analysis for use in community settings.