Medial temporal lobe atrophy on MRI scans and the diagnosis of Alzheimer disease

Neuroimaging in Alzheimer's disease: preclinical challenges toward clinical efficacy

The scope of this review focuses on recent applications in preclinical and clinical magnetic resonance imaging (MRI) toward accomplishing the goals of early detection and responses to therapy in animal models of Alzheimer's disease (AD). Driven by the outstanding efforts of the Alzheimer's Disease Neuroimaging Initiative (ADNI), a truly invaluable resource, the initial use of MRI in AD imaging has been to assess changes in brain anatomy, specifically assessing brain shrinkage and regional changes in white matter tractography using diffusion tensor imaging. However, advances in MRI have led to multiple efforts toward imaging amyloid beta plaques first without and then with the use of MRI contrast agents. These technological advancements have met with limited success and are not yet appropriate for the clinic. Recent developments in molecular imaging inclusive of high-power liposomal-based MRI contrast agents as well as fluorine 19 ((19)F) MRI and manganese enhanced MRI have begun to propel promising advances toward not only plaque imaging but also using MRI to detect perturbations in subcellular processes occurring within the neuron. This review concludes with a discussion about the necessity for the development of novel preclinical models of AD that better recapitulate human AD for the imaging to truly be meaningful and for substantive progress to be made toward understanding and effectively treating AD. Furthermore, the continued support of outstanding programs such as ADNI as well as the development of novel molecular imaging agents and MRI fast scanning sequences will also be requisite to effectively translate preclinical findings to the clinic.

Interference and conflict monitoring in individuals with amnestic mild cognitive impairment: A structural study of the anterior cingulate cortex

Amnestic mild cognitive impairment (aMCI) is a clinical condition characterized by memory impairment in the absence of any other cognitive impairment and is commonly associated with high conversion to Alzheimer's disease. Recent evidence shows that executive functions and selective attention mechanisms could also be impaired in aMCI. In this study, we investigated performance differences (i.e., reaction times [RTs] and accuracy) between a group of aMCI participants and a group of age-matched healthy individuals on the attentional network task (ANT) focusing on situations with increased interference. In particular, we assessed the relationship between interference and conflict effects and grey matter volumes (GMVs) of the anterior cingulate cortex (ACC)/pre-supplementary motor area in the entire sample because of its crucial role in conflict monitoring. When compared with controls, aMCI participants were less accurate on the ANT, showing increased interference and conflict effects, but no differences in RTs. In addition, aMCI participants exhibited lower GMV in the ACC than controls. While better accuracy for interference and conflict effects was associated with an increase of GMV in the ACC for both groups, RTs from the interference effect were negatively correlated with GMV of the ACC only in aMCI participants. In other words, lower GMV values of the ACC were paralleled with significantly impaired performance in terms of interference resolution. In conclusion, our study suggests the presence of a selective impairment in interference and conflict monitoring in aMCI, which in turn is associated with decreased GMVs in the ACC.

What can imaging tell us about cognitive impairment and dementia?

Dementia is a contemporary global health issue with far reaching consequences, not only for affected individuals and their families, but for national and global socio-economic conditions. The hallmark feature of dementia is that of irreversible cognitive decline, usually affecting memory, and impaired activities of daily living. Advances in healthcare worldwide have facilitated longer life spans, increasing the risks of developing cognitive decline and dementia in late life. Dementia remains a clinical diagnosis. The role of structural and molecular neuroimaging in patients with dementia is primarily supportive role rather than diagnostic, American and European guidelines recommending imaging to exclude treatable causes of dementia, such as tumor, hydrocephalus or intracranial haemorrhage, but also to distinguish between different dementia subtypes, the commonest of which is Alzheimer’s disease. However, this depends on the availability of these imaging techniques at individual centres. Advanced magnetic resonance imaging (MRI) techniques, such as functional connectivity MRI, diffusion tensor imaging and magnetic resonance spectroscopy, and molecular imaging techniques, such as 18F fluoro-deoxy glucose positron emission tomography (PET), amyloid PET, tau PET, are currently within the realm of dementia research but are available for clinical use. Increasingly the research focus is on earlier identification of at risk preclinical individuals, for example due to family history. Intervention at the preclinical stages before irreversible brain damage occurs is currently the best hope of reducing the impact of dementia.

Visual rating method and tensor-based morphometry in the diagnosis of mild cognitive impairment and Alzheimer's disease: a comparative magnetic resonance imaging study

BACKGROUND

Atrophy of the medial temporal lobe (MTL) is the main structural magnetic resonance imaging (MRI) finding in the brain of patients with Alzheimer's disease (AD). However, evaluating the degree of atrophy is still demanding.

PURPOSE

The visual rating method (VRM) was compared with multi-template tensor-based morphometry (TBM), in terms of its efficacy in diagnosing of mild cognitive impairment (MCI) and AD.

MATERIAL AND METHODS

Forty-seven patients with MCI, 80 patients with AD and 84 controls were studied.

RESULTS

TBM seems to be more sensitive than VRM at the early stage of dementia in the areas of MTL and ventricles. The methods were equally good in distinguishing controls and the MCI group from the AD group. At the frontal areas TBM was better than VRM in all comparisons.

CONCLUSION

A user-friendly VRM is still useful for the clinical evaluation of MCI patients, but multi-template TBM is more sensitive for diagnosing the early stages of dementia. However, TBM is currently too demanding to use for daily clinical work.

Alzheimer's disease or Alzheimer's syndrome?: a longitudinal computed tomography neuroradiological follow-up study of 56 cases diagnosed clinically as Alzheimer's disease

BACKGROUND

Some 200 patients, including those with Alzheimer's disease and other types of dementia, stay year-round in Yokohama - Houyuu Hospital. They undergo computed tomography (CT) neuroradiological examination at least once or twice a year. For this study, the accumulative data, including clinical and neuroradiological, were analyzed.

METHODS

Differential diagnoses of Alzheimer's disease were performed in accordance with the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria. The 56 patients (15 men, 41 women) included in this study underwent in-hospital observation on average for 4.4 years (range: 1-10 years). The patients were classified into four groups according to the age of disease onset. The CT findings were summarized for each group and then compared among the groups to determine if there were any differences related to age of onset and, if so, to identify and analyze them.

RESULTS

(1) The duration of deceased cases' total clinical course (in years) compared among the four groups. In general, the degree of dementia was more severe among those with earlier disease onset. (2) In cases admitted within 2 years from onset (n =14), the suspected initiating focus of cortical atrophy occurred in the frontal lobe (n = 6), the temporal lobe (n = 6), or the fronto-temporal lobes (n = 2). (3) Although CT findings generally showed that the more severe cases had earlier onset, serial CT examinations in each case showed widely different pathologies in degree, nature and manner of progression, regardless of group classification. (4) The earliest sites of brain atrophy, sites of its severest involvement within the brain, and neuroradiological development of the cerebral cortex pathology in combination with hemispheric white matter, lateral ventricles, and third ventricles varied among the four groups and between case within each group. Alzheimer's disease could not be subclassified simply by the age of clinical onset.

CONCLUSION

Cases of so-called Alzheimer's disease, as observed through continued clinical follow-up and serial CT examinations, appear so diverse in symptomatology and radiological pathomorphology that it is difficult to consider them a single nosological entity. The pathology of Alzheimer's disease has to be reconsidered in accordance with the variety observed in the sequential development of neuroradiological findings. The pathology must be reconstructed in terms of topographical dimensions and chronological developments. The diagnosis of Alzheimer's disease appears to be not so simple based on any conventional diagnostic operational standards.

Hippocampal atrophy but not white-matter changes predicts the long-term cognitive response to cholinesterase inhibitors in Alzheimer's disease

INTRODUCTION

This study aimed to investigate the feasibility of predicting the long-term effects of cholinesterase inhibitors (ChEI) with common clinical neuroimaging parameters of Alzheimer's disease, including medial temporal lobe atrophy (MTA) and white matter hyperintensity (WMH).

METHOD

A cohort of 353 patients with very mild to moderate Alzheimer's disease received cholinesterase inhibitors and were followed for a median of 46.6 months. Baseline clinical data, including age, educational level, Clinical Dementia Rating (CDR), Taiwanese Mental State Examination (TMSE), and visual scoring for MTA and WMH were tested as possible predictive factors that influence the survival from a TMSE decline of at least 3 points.

RESULTS

During the follow-up period, 162(46%) patients had a significant TMSE decline. Patients with age-adjusted prominent MTA had a significantly shorter TMSE-decline free interval than those without (43.4 ± 4.5 months vs. 68.2 ± 9.5 months, log rank test p-value =0.001). However, the severity of WMH does not significantly influence cognitive outcomes. Cox regression analysis identified that younger age at the time of starting ChEI (p < 0.0005) and higher total MTA scores (p = 0.002) predict a more rapid TMSE decline under ChEI therapy.

CONCLUSIONS

Younger age at the time of starting ChEI and higher visual scoring of MTA may imply a more advanced Alzheimer's pathology. WMH load is not a prognostic indicator of treatment response to ChEI.

Using visual rating to diagnose dementia: a critical evaluation of MRI atrophy scales

Visual rating scales, developed to assess atrophy in patients with cognitive impairment, offer a cost-effective diagnostic tool that is ideally suited for implementation in clinical practice. By focusing attention on brain regions susceptible to change in dementia and enforcing structured reporting of these findings, visual rating can improve the sensitivity, reliability and diagnostic value of radiological image interpretation. Brain imaging is recommended in all current diagnostic guidelines relating to dementia, and recent guidelines have also recommended the application of medial temporal lobe atrophy rating. Despite these recommendations, and the ease with which rating scales can be applied, there is still relatively low uptake in routine clinical assessments. Careful consideration of atrophy rating scales is needed to verify their diagnostic potential and encourage uptake among clinicians. Determining the added value of combining scores from visual rating in different brain regions may also increase the diagnostic value of these tools.

Are transversal MR images sufficient to distinguish persons with mild cognitive impairment from healthy controls?

RATIONALE AND OBJECTIVES

Mild cognitive impairment (MCI) is associated with an increased risk of developing dementia. This study aims to determine whether current standard magnetic resonance imaging (MRI) is providing markers that can distinguish between subjects with amnestic MCI (aMCI), nonamnestic MCI (naMCI), and healthy controls (HCs).

MATERIALS AND METHODS

A subset of 126 MCI subjects and 126 age-, gender-, and education-appropriate HCs (mean age, 70.9 years) were recruited from 4157 participants in the longitudinal community-based Heinz Nixdorf Recall Study. The burden of white matter hyperintensities (WMHs), cerebral microbleeds, and brain atrophy was evaluated on transversal MR images from a single 1.5-T MR scanner by two blinded neuroradiologists. Logistic regression and receiver-operating characteristic analysis were used for statistical analysis.

RESULTS

Occipital WMH burden was significantly increased in aMCI, but not in naMCI relative to HCs (P = .01). The combined MCI group showed brain atrophy relative to HCs (P = .01) pronounced at caudate nuclei (P = .01) and temporal horn level (P = .004) of aMCI patients and increased at the frontal and occipital horns of naMCI patients compared to either aMCI or HCs. Microbleeds were equally distributed in the MCI and control group, but more frequent in aMCI (22 of 84) compared to naMCI subjects (3 of 23).

CONCLUSIONS

In his cohort, increased occipital WMHs and cortical and subcortical brain atrophies at temporal horn and caudate nuclei level distinguished aMCI from naMCI subjects and controls. Volumetric indices appear of interest and should be assessed under reproducible conditions to gain diagnostic accuracy.

Multimodal imaging in Alzheimer's disease: validity and usefulness for early detection

Alzheimer's disease is a progressive neurodegenerative disease that typically manifests clinically as an isolated amnestic deficit that progresses to a characteristic dementia syndrome. Advances in neuroimaging research have enabled mapping of diverse molecular, functional, and structural aspects of Alzheimer's disease pathology in ever increasing temporal and regional detail. Accumulating evidence suggests that distinct types of imaging abnormalities related to Alzheimer's disease follow a consistent trajectory during pathogenesis of the disease, and that the first changes can be detected years before the disease manifests clinically. These findings have fuelled clinical interest in the use of specific imaging markers for Alzheimer's disease to predict future development of dementia in patients who are at risk. The potential clinical usefulness of single or multimodal imaging markers is being investigated in selected patient samples from clinical expert centres, but additional research is needed before these promising imaging markers can be successfully translated from research into clinical practice in routine care.

Relationship of contextual cueing and hippocampal volume in amnestic mild cognitive impairment patients and cognitively normal older adults

There is currently some debate as to whether hippocampus mediates contextual cueing. In the present study, we examined contextual cueing in patients diagnosed with mild cognitive impairment (MCI) and healthy older adults, with the main goal of investigating the role of hippocampus in this form of learning. Amnestic MCI (aMCI) patients and healthy controls completed the contextual cueing task, in which they were asked to search for a target (a horizontal T) in an array of distractors (rotated L's). Unbeknownst to them, the spatial arrangement of elements on some displays was repeated thus making the configuration a contextual cue to the location of the target. In contrast, the configuration for novel displays was generated randomly on each trial. The difference in response times between repeated and novel configurations served as a measure of contextual learning. aMCI patients, as a group, were able to learn spatial contextual cues as well as healthy older adults. However, better learning on this task was associated with higher hippocampal volume, particularly in right hemisphere. Furthermore, contextual cueing performance was significantly associated with hippocampal volume, even after controlling for age and MCI status. These findings support the role of the hippocampus in learning of spatial contexts, and also suggest that the contextual cueing paradigm can be useful in detecting neuropathological changes associated with the hippocampus.

T1rho MRI and CSF biomarkers in diagnosis of Alzheimer's disease

In the current study, we have evaluated the performance of magnetic resonance (MR) T1rho (T_1ρ) imaging and CSF biomarkers (T-tau, P-tau and Aβ-42) in characterization of Alzheimer's disease (AD) patients from mild cognitive impairment (MCI) and control subjects. With informed consent, AD (n = 27), MCI (n = 17) and control (n = 17) subjects underwent a standardized clinical assessment and brain MRI on a 1.5-T clinical-scanner. T_1ρ images were obtained at four different spin-lock pulse duration (10, 20, 30 and 40 ms). T_1ρ maps were generated by pixel-wise fitting of signal intensity as a function of the spin-lock pulse duration. T_1ρ values from gray matter (GM) and white matter (WM) of medial temporal lobe were calculated. The binary logistic regression using T_1ρ and CSF biomarkers as variables was performed to classify each group. T_1ρ was able to predict 77.3% controls and 40.0% MCI while CSF biomarkers predicted 81.8% controls and 46.7% MCI. T_1ρ and CSF biomarkers in combination predicted 86.4% controls and 66.7% MCI. When comparing controls with AD, T_1ρ predicted 68.2% controls and 73.9% AD, while CSF biomarkers predicted 77.3% controls and 78.3% for AD. Combination of T_1ρ and CSF biomarkers improved the prediction rate to 81.8% for controls and 82.6% for AD. Similarly, on comparing MCI with AD, T_1ρ predicted 35.3% MCI and 81.9% AD, whereas CSF biomarkers predicted 53.3% MCI and 83.0% AD. Collectively CSF biomarkers and T_1ρ were able to predict 59.3% MCI and 84.6% AD. On receiver operating characteristic analysis T_1ρ showed higher sensitivity while CSF biomarkers showed greater specificity in delineating MCI and AD from controls. No significant correlation between T_1ρ and CSF biomarkers, between T_1ρ and age, and between CSF biomarkers and age was observed. The combined use of T_1ρ and CSF biomarkers have promise to improve the early and specific diagnosis of AD. Furthermore, disease progression form MCI to AD might be easily tracked using these two parameters in combination.

•

Increased T1rho was observed in MCI and AD compared to controls.

•

Increased T-tau and P-tau and decreased Aβ1-42 were observed in MCI and AD.

•

Combined biomarkers have promise to improve early and specific diagnosis of AD.

•

MCI to AD progression might be tracked using these two biomarkers in combination.

Visual rating and volumetric measurement of medial temporal atrophy in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort: baseline diagnosis and the prediction of MCI outcome

OBJECTIVE

This study aims to determine the clinical utility of visual ratings and volumetric measurements of medial temporal atrophy among subjects from the Alzheimer's Disease Neurorimaging Initiative (ADNI) cohort.

METHODS

A sample of 189 subjects from the ADNI, Phase 1 (ADNI-1), was chosen as follows: 49 cognitively normal (CN), 89 with mild cognitive impairment (MCI), and 50 with Alzheimer's disease (AD). Structural MRI images were downloaded from the ADNI website, and a visual rating system (VRS) was used to obtain semi-quantitative ratings of the hippocampus (HPC) and entorhinal cortex (ERC). VRS ratings and FreeSurfer measures of the HPC and ERC were used to predict (i) baseline diagnosis and (ii) progression to AD among subjects with MCI at baseline.

RESULTS

VRS and FreeSurfer measures of ERC were equivalent in classifying subjects at baseline, but FreeSurfer measures of HPC were superior to VRS measures for classifying CN versus MCI subjects. VRS and FreeSurfer measures of both HPC and ERC were significant predictors of progression from MCI to AD. However, VRS ratings of ERC were superior to other MRI measures. MCI subjects with minimal ERC atrophy by VRS had a threefold lower progression rate to AD at 3.2 years compared with those with mild, moderate, or severe atrophy (23% vs 63%, 69%, and 87%, respectively).

CONCLUSIONS

Visual ratings of HPC and ERC provide useful information to a physician in a clinical setting. Visual ratings of ERC may be especially useful in following patients with MCI.

Running exercise delays neurodegeneration in amygdala and hippocampus of Alzheimer's disease (APP/PS1) transgenic mice

Alzheimer's disease (AD) is an age-related neurodegenerative disease. Post-mortem examination and brain imaging studies indicate that neurodegeneration is evident in the hippocampus and amygdala of very early stage AD patients. Exercise training is known to enhance hippocampus- and amygdala-associated neuronal function. Here, we investigated the effects of exercise (running) on the neuronal structure and function of the hippocampus and amygdala in APP/PS1 transgenic (Tg) mice. At 4-months-old, an age before amyloid deposition, the amygdala-associated, but not the hippocampus-associated, long-term memory was impaired in the Tg mice. The dendritic complexities of the amygdalar basolateral neurons, but not those in the hippocampal CA1 and CA3 neurons, were reduced. Furthermore, the levels of BDNF/TrkB signaling molecules (i.e. p-TrkB, p-Akt and p-PKC) were reduced in the amygdala, but not in the hippocampus of the 4-month-old Tg mice. The concentrations of Aβ40 and Aβ42 in the amygdala were higher than those in the hippocampus. Ten weeks of treadmill training (from 1.5- to 4-month-old) increased the hippocampus-associated memory and dendritic arbor of the CA1 and CA3 neurons, and also restored the amygdala-associated memory and the dendritic arbor of amygdalar basolateral neurons in the Tg mice. Similarly, exercise training also increased the levels of p-TrkB, p-AKT and p-PKC in the hippocampus and amygdala. Furthermore, exercise training reduced the levels of soluble Aβ in the amygdala and hippocampus. Exercise training did not change the levels of APP or RAGE, but significantly increased the levels of LRP-1 in both brain regions of the Tg mice. In conclusion, our results suggest that tests of amygdala function should be incorporated into subject selection for early prevention trials. Long-term exercise protects neurons in the amygdala and hippocampus against AD-related degeneration, probably via enhancements of BDNF signaling pathways and Aβ clearance. Physical exercise may serve as a means to delay the onset of AD.

Biomarkers in dementia: clinical utility and new directions

Imaging, cerebrospinal fluid (CSF) and blood-based biomarkers have the potential to improve the accuracy by which specific causes of dementia can be diagnosed in vivo, provide insights into the underlying pathophysiology, and may be used as inclusion criteria and outcome measures for clinical trials. While a number of imaging and CSF biomarkers are currently used for each of these purposes, this is an evolving field, with numerous potential biomarkers in varying stages of research and development. We review the currently available biomarkers for the three most common forms of neurodegenerative dementia, and give an overview of research techniques that may in due course make their way into the clinic.

Using neuroimaging to inform clinical practice for the diagnosis and treatment of mild cognitive impairment

Advances in structural and functional neuroimaging techniques have unquestionably improved understanding of the development and progression of Alzheimer disease (AD), with evidence supporting regional (and network) change that underlies cognitive decline across the "healthy" aging/mild cognitive impairment (MCI)/AD spectrum. This review focuses on visual rating scales and volumetric analyses that could be easily integrated into clinical practice, followed by a review of functional neuroimaging findings suggesting that widespread cerebral dysfunction underlies the learning and memory deficits in MCI. Evidence of preserved neuroplasticity in this population and that cognitive rehabilitation techniques may capitalize on this plasticity to improve cognition in those with MCI is also discussed.

Neuroimaging in dementia

Over the last few years, advances in neuroimaging have generated biomarkers, which increase diagnostic certainty, provide valuable information about prognosis, and suggest a particular pathology underlying the clinical dementia syndrome. We aim to review the evidence for use of already established imaging modalities, along with selected techniques that have a great potential to guide clinical decisions in the future. We discuss structural, functional and molecular imaging, focusing on the most common dementias: Alzheimer's disease, fronto-temporal dementia, dementia with Lewy bodies and vascular dementia. Finally, we stress the importance of conducting research using representative cohorts and in a naturalistic set up, in order to build a strong evidence base for translating imaging methods for a National Health Service. If we assess a broad range of patients referred to memory clinic with a variety of imaging modalities, we will make a step towards accumulating robust evidence and ultimately closing the gap between the dramatic advances in neurosciences and meaningful clinical applications for the maximum benefit of our patients.

Influence of age, disease onset and ApoE4 on visual medial temporal lobe atrophy cut-offs

BACKGROUND

Visual assessment of medial temporal lobe atrophy (MTA; range 0-4, from no atrophy to increasing atrophy of the choroid fissure, temporal horns and hippocampus) is a sensitive radiological marker of Alzheimer's disease (AD). One of the critical elements for visual MTA assessment is the cut-off score that determines deviation from normality.

METHODS

In this study, we assessed the sensitivity and specificity of different MTA cut-off scores to classify control subjects, individuals with mild cognitive impairment (MCI) and AD patients from two large independent cohorts, AddNeuroMed and Alzheimer's Disease Neuroimaging Initiative. Of note, we evaluated the effects of clinical, demographic and genetic variables on the classification performance according to the different cut-offs.

RESULTS

A cut-off of ≥1.5 based on the mean MTA scores of both hemispheres showed higher sensitivity in classifying patients with AD (84.5%) and MCI subjects (75.8%) who converted to dementia compared to an age-dependent cut-off. The age-dependent cut-off showed higher specificity or ability to correctly identify control subjects (83.2%) and those with MCI who remained stable (65.5%). Increasing age, early-onset disease and absence of the ApoE ε4 allele had a stronger influence on classifications using the ≥1.5 cut-off. Above 75 years of age, an alternative cut-off of ≥2.0 should be applied to achieve a classification accuracy for both patients with AD and control subjects that is clinically useful.

CONCLUSION

Clinical, demographic and genetic variables can influence the classification of MTA cut-off scores, leading to misdiagnosis in some cases. These variables, in addition to the differential sensitivity and specificity of each cut-off, should be carefully considered when performing visual MTA assessment.

Evaluation of common structural brain changes in aging and Alzheimer disease with the use of an MRI-based brain atrophy and lesion index: a comparison between T1WI and T2WI at 1.5T and 3T

BACKGROUND AND PURPOSE

The Brain Atrophy and Lesion Index combines several common, aging-related structural brain changes and has been validated for high-field MR imaging. In this study, we evaluated measurement properties of the Brain Atrophy and Lesion Index by use of T1WI and T2WI at 1.5T and 3T MR imaging to comprehensively assess the usefulness of the lower field-strength testing.

MATERIALS AND METHODS

Data were obtained from the Alzheimer's Disease Neuroimaging Initiative. Images of subjects (n = 127) who had T1WI and T2WI at both 3T and 1.5T on the same day were evaluated, applying the Brain Atrophy and Lesion Index rating. Criterion and construct validity and interrater agreement were tested for each field strength and image type.

RESULTS

Regarding reliability, the intraclass correlation coefficients for the Brain Atrophy and Lesion Index score were consistently high (>0.81) across image type and field strength. Regarding construct validity, the Brain Atrophy and Lesion Index score differed among diagnostic groups, being lowest in people without cognitive impairment and highest in those with Alzheimer disease (F > 5.14; P < .007). Brain Atrophy and Lesion Index scores correlated with age (r > 0.37, P < .001) and cognitive performance (r > 0.38, P < .001) and were associated with positive amyloid-β test (F > 3.96, P < .050). The T1WI and T2WI Brain Atrophy and Lesion Index scores were correlated (r > 0.93, P < .001), with the T2WI scores slightly greater than the T1WI scores (F > 4.25, P < .041). Regarding criterion validation of the 1.5T images, the 1.5T scores were highly correlated with the 3T Brain Atrophy and Lesion Index scores (r > 0.93, P < .001).

CONCLUSIONS

The higher field and T2WI more sensitively detect subtle changes in the deep white matter and perivascular spaces in particular. Even so, 1.5T Brain Atrophy and Lesion Index scores are similar to those obtained by use of 3T images. The Brain Atrophy and Lesion Index may have use in quantifying the impact of dementia on brain structures.

MR anatomy of deep brain nuclei with special reference to specific diseases and deep brain stimulation localization

Diseases affecting the basal ganglia and deep brain structures vary widely in etiology and include metabolic, infectious, ischemic, and neurodegenerative conditions. Some neurologic diseases, such as Wernicke encephalopathy or pseudohypoparathyroidism, require specific treatments, which if unrecognized could lead to further complications. Other pathologies, such as hypertrophic olivary degeneration, if not properly diagnosed may be mistaken for a primary medullary neoplasm and create unnecessary concern. The deep brain structures are complex and can be difficult to distinguish on routine imaging. It is imperative that radiologists first understand the intrinsic anatomic relationships between the different basal ganglia nuclei and deep brain structures with magnetic resonance (MR) imaging. It is important to understand the "normal" MR signal characteristics, locations, and appearances of these structures. This is essential to recognizing diseases affecting the basal ganglia and deep brain structures, especially since most of these diseases result in symmetrical, and therefore less noticeable, abnormalities. It is also crucial that neurosurgeons correctly identify the deep brain nuclei presurgically for positioning deep brain stimulator leads, the most important being the subthalamic nucleus for Parkinson syndromes and the thalamic ventral intermediate nucleus for essential tremor. Radiologists will be able to better assist clinicians in diagnosis and treatment once they are able to accurately localize specific deep brain structures.

The appropriate use of neuroimaging in the diagnostic work-up of dementia: an evidence-based analysis

BACKGROUND

Diagnosis of dementia is challenging and requires both ruling out potentially treatable underlying causes and ruling in a diagnosis of dementia subtype to manage patients and suitably plan for the future.

OBJECTIVES

This analysis sought to determine the appropriate use of neuroimaging during the diagnostic work-up of dementia, including indications for neuroimaging and comparative accuracy of alternative technologies.

DATA SOURCES

A literature search was performed using Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid Embase, the Wiley Cochrane Library, and the Centre for Reviews and Dissemination database, for studies published between 2000 and 2013.

REVIEW METHODS

Data on diagnostic accuracy and impact on clinical decision making were abstracted from included studies. Quality of evidence was assessed using GRADE.

RESULTS

The search yielded 5,374 citations and 15 studies were included. Approximately 10% of dementia cases are potentially treatable, though less than 1% reverse partially or fully. Neither prediction rules nor clinical indications reliably select the subset of patients who will likely benefit from neuroimaging. Clinical utility is highest in ambiguous cases or where dementia may be mixed, and lowest for clinically diagnosed Alzheimer disease or clinically excluded vascular dementia. There is a lack of evidence that MRI is superior to CT in detecting a vascular component to dementia. Accuracy of structural imaging is moderate to high for discriminating different types of dementia.

LIMITATIONS

There was significant heterogeneity in estimates of diagnostic accuracy, which often prohibited a statistical summary of findings. The quality of data reported by studies prohibited calculation of likelihood ratios in the present analysis. No studies from primary care were found; thus, generalizability beyond tertiary care settings may be limited.

CONCLUSIONS

A diagnosis of reversible dementia is rare. Imaging has the most clinical utility in cases where there is potentially mixed dementia or ambiguity as to the type of dementia despite prolonged follow-up (e.g., 2 years or more). Both CT and MRI are useful for detecting a vascular component of dementia.

Full diffusion characterization implicates regionally disparate neuropathology in mild cognitive impairment

Diffusion tensor imaging (DTI) is used to detect tissue pathology. In Alzheimer's disease (AD) research, DTI has been used to elucidate differences in disease stages and to track progression over time and clinical severity. Many of these studies have identified the fornix as particularly vulnerable in the early stages of pathology associated with memory decline in prodromal AD. Emerging research suggests principal tensor components, axial (DA) and radial (DR) diffusivity, are more sensitive to underlying tissue pathology than are mean diffusivity (MD) and fractional anisotropy (FA). Given the established regionally specific tissue decline in MCI, we examined components of the full diffusion tensor (MD, FA, DR, and DA) for sensitivity to regional pathology associated with specific memory deficits in 18 individuals with MCI. We investigated multiple regions of interest, including fornix, temporal stem, and control regions for association with severity of impairment on multiple memory measures, including a type of neuropsychological task shown to be particularly sensitive to early memory decline in MCI. Better paired associate learning was selectively associated with lower DA (β = -0.663, p = 0.003), but not with DR, MD, or FA of the temporal stems. Conversely, better paired associate learning was associated with lower DR (β = -0.523, p = 0.026), higher FA (β = 0.498, p = 0.036), and lower MD (β = -0.513, p = 0.030), but not DA in the fornix. No association was found for control regions, or for control cognitive measures. These findings suggest disparate pathology of temporal stems and fornix white matter in association with early memory impairment in MCI. Further, they highlight the methodological importance of evaluating the full tensor, rather than only summative metrics in research using DTI.

Comparing regional brain atrophy in mild cognitive impairment and Alzheimer’s disease

SUMMARY Neuroimaging has assumed an active role in the diagnosis of Alzheimer’s disease (AD) and other dementias. Structural MRI can estimate changes in specific brain structures relative to normal and pathological aging such as volume, cortical thickness and gray matter density. Several different structural MRI methods can be used to identify neuropathology and point to an early atrophy in medial temporal lobe structures in patients with AD and amnestic mild cognitive impairment, especially in the entorhinal cortex and hippocampus. These alterations in medial temporal lobe structures were also considered evidence for neurodegeneration, even in preclinical AD. However, evaluation in other areas such as ventricular enlargement and precuneus may help the diagnosis, even in the early stages of the disease. Currently, neuroimaging is an excellent tool for increasing diagnostic accuracy, but does not substitute a careful clinical and neuropsychological evaluation. In this article, our objective is to gather information about different structural MRI-based methods that could offer objective measures of brain structures and increase the diagnostic power of mild cognitive impairment and AD.

The utility of age-specific cut-offs for visual rating of medial temporal atrophy in classifying Alzheimer's disease, MCI and cognitively normal elderly subjects

Background: New research criteria for diagnosing Alzheimer's disease (AD) in the mild cognitive impairment stage (MCI-AD) incorporate biomarkers to assign a level of certainty to the diagnosis. Structural MRI is widely available but greatly under-utilized for assessing atrophy of structures affected in early AD, such as the hippocampus (HP), because the quantification of HP volumes (HP-v) requires special expertise, and normative values have not been established.

Methods: Elderly subjects (n =273) from the Florida ADRC were classified as having no cognitive impairment (cognitively normal, CN), amnestic mild cognitive impairment (aMCI) or AD. Volumes for the hippocampus (HP-v) were measured on structural MRI scans. A validated visual rating system for measuring medial temporal atrophy (VRS-MTA), including hippocampal, entorhinal cortex and perirhinal cortex atrophy was employed. The participants were subdivided into younger (less than or equal to 75 years of age) and older (greater than 75 years of age) subgroups.

Results: Volumetric and VRS-MTA measures were equivalent in predicting classification of CN vs. aMCI for older (area under the receiver operator curves [aROC]: 0.652 vs. 0.723) and younger subjects (aROC: 0.764 vs. 0.736). However, for younger AD subjects, aROC values were significantly higher for VRS-MTA measures (0.920) than for volumetric measures (0.847). Relative to HP-v, VRS-MTA score was significantly more correlated to impairment on a range of memory tests and was more associated with progression of aMCI to AD than HP-v.

Conclusion: Structural MRI with VRS-MTA assessment can serve as a biomarker for supporting the diagnosis of MCI-AD. Age-adjusted VRS-MTA scores are at least as effective as HP-v for distinguishing aMCI and AD from CN and for predicting progression from aMCI to AD. VRS-MTA is convenient for use in the clinic as well as for clinical trials and can readily be incorporated into a standardized radiological report.

Clinical applications of neuroimaging in patients with Alzheimer's disease: a review from the Fourth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia 2012

In May 2012, the Fourth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia brought together in Montreal experts from around Canada to update Canadian recommendations for the diagnosis and management of patients with neurodegenerative conditions associated with deterioration of cognition. Multiple topics were discussed. The present paper is a highly condensed version of those recommendations that were produced to support discussions in the field of neuroimaging for clinical diagnosis of those conditions.

Brain imaging in Alzheimer disease

Imaging has played a variety of roles in the study of Alzheimer disease (AD) over the past four decades. Initially, computed tomography (CT) and then magnetic resonance imaging (MRI) were used diagnostically to rule out other causes of dementia. More recently, a variety of imaging modalities including structural and functional MRI and positron emission tomography (PET) studies of cerebral metabolism with fluoro-deoxy-d-glucose (FDG) and amyloid tracers such as Pittsburgh Compound-B (PiB) have shown characteristic changes in the brains of patients with AD, and in prodromal and even presymptomatic states that can help rule-in the AD pathophysiological process. No one imaging modality can serve all purposes as each have unique strengths and weaknesses. These modalities and their particular utilities are discussed in this article. The challenge for the future will be to combine imaging biomarkers to most efficiently facilitate diagnosis, disease staging, and, most importantly, development of effective disease-modifying therapies.

Microstructural white matter changes, not hippocampal atrophy, detect early amnestic mild cognitive impairment

BACKGROUND

Alzheimer's disease (AD) is generally considered to be characterized by pathology in gray matter of the brain, but convergent evidence suggests that white matter degradation also plays a vital role in its pathogenesis. The evolution of white matter deterioration and its relationship with gray matter atrophy remains elusive in amnestic mild cognitive impairment (aMCI), a prodromal stage of AD.

METHODS

We studied 155 cognitively normal (CN) and 27 'late' aMCI individuals with stable diagnosis over 2 years, and 39 'early' aMCI individuals who had converted from CN to aMCI at 2-year follow up. Diffusion tensor imaging (DTI) tractography was used to reconstruct six white matter tracts three limbic tracts critical for episodic memory function - the fornix, the parahippocampal cingulum, and the uncinate fasciculus; two cortico-cortical association fiber tracts - superior longitudinal fasciculus and inferior longitudinal fasciculus; and one projection fiber tract - corticospinal tract. Microstructural integrity as measured by fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AxD) was assessed for these tracts.

RESULTS

Compared with CN, late aMCI had lower white matter integrity in the fornix, the parahippocampal cingulum, and the uncinate fasciculus, while early aMCI showed white matter damage in the fornix. In addition, fornical measures were correlated with hippocampal atrophy in late aMCI, whereas abnormality of the fornix in early aMCI occurred in the absence of hippocampal atrophy and did not correlate with hippocampal volumes.

CONCLUSIONS

Limbic white matter tracts are preferentially affected in the early stages of cognitive dysfunction. Microstructural degradation of the fornix preceding hippocampal atrophy may serve as a novel imaging marker for aMCI at an early stage.

The diagnosis and evaluation of dementia and mild cognitive impairment with emphasis on SPECT perfusion neuroimaging

As the world population ages, the incidence of dementing illnesses will dramatically increase. The number of people afflicted with dementia is expected to quadruple in the next 50 years. Since the neuropathology of the dementias precedes clinical symptoms often by several years, earlier detection and intervention could be key steps to mitigating the progression and burden of these diseases. This review will explore methods of evaluating, differentiating, and diagnosing the multiple forms of dementia. Particular emphasis will be placed on the diagnosis of mild cognitive impairment-the precursor to dementia. Anatomical imaging; cerebrospinal fluid markers; functional neuroimaging, such as positron emission tomography and single photon emission tomography; and molecular imaging, such as amyloid marker imaging, will be assessed in terms of sensitivity and specificity. Cost will also be a consideration, as the growing population afflicted with dementia represents an increasingly large financial encumbrance to the healthcare systems of every nation. In the face of expensive new markers and limited availability of cyclotrons, single photon emission computer tomography (SPECT) provides relatively high sensitivity and specificity at a comparatively low overall cost.

Amyloid positron emission tomography with (18)F-flutemetamol and structural magnetic resonance imaging in the classification of mild cognitive impairment and Alzheimer's disease

OBJECTIVE

To evaluate the contributions of amyloid-positive (Am+) and medial temporal atrophy-positive (MTA+) scans to the diagnostic classification of prodromal and probable Alzheimer's disease (AD).

METHODS

(18)F-flutemetamol-labeled amyloid positron emission tomography (PET) and magnetic resonance imaging (MRI) were used to classify 10 young normal, 15 elderly normal, 20 amnestic mild cognitive impairment (aMCI), and 27 AD subjects. MTA+ status was determined using a cut point derived from a previous study, and Am+ status was determined using a conservative and liberal cut point.

RESULTS

The rates of MRI scans with positive results among young normal, elderly normal, aMCI, and AD subjects were 0%, 20%, 75%, and 82%, respectively. Using conservative cut points, the rates of Am+ scans for these same groups of subjects were 0%, 7%, 50%, and 93%, respectively, with the aMCI group showing the largest discrepancy between Am+ and MTA+ scans. Among aMCI cases, 80% of Am+ subjects were also MTA+, and 70% of amyloid-negative (Am-) subjects were MTA+. The combination of amyloid PET and MTA data was additive, with an overall correct classification rate for aMCI of 86%, when a liberal cut point (standard uptake value ratio = 1.4) was used for amyloid positivity.

INTERPRETATION

(18)F-flutemetamol PET and structural MRI provided additive information in the diagnostic classification of aMCI subjects, suggesting an amyloid-independent neurodegenerative component among aMCI subjects in this sample.

Global gray matter changes in posterior cortical atrophy: a serial imaging study

BACKGROUND

Posterior cortical atrophy (PCA) is a neurodegenerative condition predominantly associated with Alzheimer's disease (AD) pathology. Cross-sectional imaging studies have shown different atrophy patterns in PCA patients compared with typical amnestic Alzheimer's disease (tAD) patients, with greatest atrophy commonly found in posterior regions in the PCA group, whereas in the tAD group, atrophy is most prominent in medial temporal lobe regions. However, differential longitudinal atrophy patterns are not well understood.

METHODS

This study assessed longitudinal changes in brain and gray matter volumes in 17 PCA patients, 16 tAD patients, and 18 healthy control subjects. Both patient groups had symptom durations of approximately 5 years.

RESULTS

Progressive gray matter losses in both PCA and tAD patients were relatively widespread throughout the cortex, compared with control subjects, and were not confined to areas related to initial symptomatology. A multivariate classification analysis revealed a statistically significant group separation between PCA and tAD patients, with 72.7% accuracy (P < .01).

CONCLUSION

Progression from an initially focal presentation to a more global pattern suggests that these different clinical presentations of AD might converge pathologically over time.

Neuroimaging in dementias

PURPOSE OF REVIEW

To critically review data on the use of neuroimaging tools in the clinical diagnostic investigation of dementias.

RECENT FINDINGS

For many years, the use of neuroimaging tools in the evaluation of dementias has been restricted to excluding neurosurgical lesions that may account for the cognitive decline. However, modern neuroimaging extends beyond this traditional role of excluding other conditions and has a key role in the clinical investigation of Alzheimer's disease and of other degenerative cortical dementias. MRI, PET with fluorodeoxyglucose, and single-photon emission computed tomography are topographic markers of neural damage and enable the identification of specific lesional patterns that characterize Alzheimer's disease and other cortical dementias. More recently, PET amyloid markers have enabled the in-vivo assessment of amyloid load, a key feature in the physiopathology of Alzheimer's disease.

SUMMARY

The combined use of neuroimaging examinations with clinical, neuropsychological, and cerebrospinal fluid markers can improve the specificity of the diagnosis of Alzheimer's disease, even at early stages of the disease. In the following years, progress in research will provide standardized and validated imaging markers of Alzheimer's disease and other dementias, which may increase their application in clinical settings.

Cross-validation of brain structural biomarkers and cognitive aging in a community-based study

BACKGROUND

Population-based studies face challenges in measuring brain structure relative to cognitive aging. We examined the feasibility of acquiring state-of-the-art brain MRI images at a community hospital, and attempted to cross-validate two independent approaches to image analysis.

METHODS

Participants were 49 older adults (29 cognitively normal and 20 with mild cognitive impairment (MCI)) drawn from an ongoing cohort study, with annual clinical assessments within one month of scan, without overt cerebrovascular disease, and without dementia (Clinical Dementia Rating (CDR) < 1). Brain MRI images, acquired at the local hospital using the Alzheimer's Disease Neuroimaging Initiative protocol, were analyzed using (1) a visual atrophy rating scale and (2) a semi-automated voxel-level morphometric method. Atrophy and volume measures were examined in relation to cognitive classification (any MCI and amnestic MCI vs. normal cognition), CDR (0.5 vs. 0), and presumed etiology.

RESULTS

Measures indicating greater atrophy or lesser volume of the hippocampal formation, the medial temporal lobe, and the dilation of the ventricular space were significantly associated with cognitive classification, CDR = 0.5, and presumed neurodegenerative etiology, independent of the image analytic method. Statistically significant correlations were also found between the visual ratings of medial temporal lobe atrophy and the semi-automated ratings of brain structural integrity.

CONCLUSIONS

High quality MRI data can be acquired and analyzed from older adults in population studies, enhancing their capacity to examine imaging biomarkers in relation to cognitive aging and dementia.

New visual rating system for medial temporal lobe atrophy: a simple diagnostic tool for routine examinations

AIM

We estimated the usefulness of our new scale to rate medial temporal atrophy with short inversion time inversion recovery images.

METHODS

Alzheimer's disease (AD) subjects (n= 34) and non-demented subjects (n= 19) were recruited for this study. First, coronal short inversion time inversion recovery images were scanned vertical to the long axis of hippocampus. Next, the single image in which peduncles appeared widest was adopted for estimation. The parahippocampal cerebrospinal fluid space was divided into three parts: the outer, upper and inner parts. The hippocampus was defined as a structure being of equal intensity to grey matter. Two radiologists compared each part of the parahippocampal cerebrospinal fluid space with the hippocampus and rated them on a 0-3 scale. Interrater and intrarater kappa statistics and sensitivity/specificity for the diagnosis of AD were calculated using the scores of the right, left and both sides combined.

RESULTS

There were no significant differences between AD and ND subjects with regards to sex. AD subjects had lower Mini-Mental State Examination scores and were older than non-demented subjects. Interrater and intrarater kappa statistics were 0.52-0.68 and 0.76-0.83, respectively. Sensitivity was 88.2% using the scores of both sides.

CONCLUSIONS

Interrater and intrarater agreements were fair to good and good to excellent, respectively. Our new visual rating method detected medial temporal atrophy in AD patients at a highly sensitive rate. As such, we conclude that this visual rating scale is useful for judging medial temporal atrophy simply and objectively in clinical use, and it is helpful in establishing an AD diagnosis.

Posterior cerebral atrophy in the absence of medial temporal lobe atrophy in pathologically-confirmed Alzheimer's disease

Medial temporal lobe atrophy (MTA) is a recognized marker of Alzheimer's disease (AD), however, it can be prominent in frontotemporal lobar degeneration (FTLD). There is an increasing awareness that posterior atrophy (PA) is important in AD and may aid the differentiation of AD from FTLD. Visual rating scales are a convenient way of assessing atrophy in a clinical setting. In this study, 2 visual rating scales measuring MTA and PA were used to compare atrophy patterns in 62 pathologically-confirmed AD and 40 FTLD patients. Anatomical correspondence of MTA and PA was assessed using manually-delineated regions of the hippocampus and posterior cingulate gyrus, respectively. Both MTA and PA scales showed good inter- and intrarater reliabilities (kappa > 0.8). MTA scores showed a good correspondence with manual hippocampal volumes. Thirty percent of the AD patients showed PA in the absence of MTA. Adding the PA to the MTA scale improved discrimination of AD from FTLD, and early-onset AD from normal aging. These results underline the importance of considering PA in AD diagnosis, particularly in younger patients where medial temporal atrophy may be less conspicuous.

Correlation between volume and morphological changes in the hippocampal formation in Alzheimer's disease: rounding of the outline of the hippocampal body on coronal MR images

INTRODUCTION

The aim of this study was to investigate whether the outline of the hippocampal body becomes rounded on coronal magnetic resonance imaging (MRI) as the volume of the hippocampal formation decreases in Alzheimer's disease (AD).

METHODS

Institutional review board approval of the study protocol was obtained, and all subjects provided informed consent for the mini-mental state examination (MMSE) and MRI. The MRI and MMSE were prospectively performed in all 103 subjects (27 men and 76 women; mean age ± standard deviation, 77.7 ± 7.8 years) who had AD or were concerned about having of dementia and who consulted our institute over 1 year. The subjects included 14 non-dementia cases (MMSE score ≥ 28) and 89 AD cases (MMSE score ≤ 27). The total volume of the bilateral hippocampal formation (VHF) was assessed with a tracing method, and the ratio of the VHF to the intracranial volume (RVHF) and the rounding ratio (RR) of the hippocampal body (mean ratio of its short dimension to the long dimension in the bilateral hippocampal body) were calculated. Using Spearman's correlation coefficient, the correlations between RR and VHF and between RR and RVHF were assessed.

RESULTS

Correlation coefficients between RR and VHF and between RR and RVHF were -0.419 (p < 0.01) and -0.418 (p < 0.01), respectively. There was a significant negative correlation between RR and the volume of the hippocampal formation.

CONCLUSION

The outline of the body of the hippocampal formation becomes rounded on coronal images as its volume decreases in AD.

Combining structural brain changes improves the prediction of Alzheimer's disease and mild cognitive impairment

BACKGROUND

Several structural brain changes have been associated with Alzheimer's disease (AD). This study investigated the prediction of AD by combining multiple brain changes with the hallmark medial temporal lobe atrophy (MTA).

METHODS

High-resolution magnetic resonance imaging (MRI) data of people with mild AD (n = 39), mild cognitive impairment (MCI; n = 82), and of healthy controls (HC; n = 58) were obtained at baseline. Among these people, 26 AD, 53 MCI, and 46 HC subjects had 24-month follow-up MRI scans. Bilateral MTA was evaluated using a medial temporal lobe atrophy scale (MTAS). Common changes in the aging brain were summarized using a brain atrophy and lesion index (BALI). The performance of the MTAS, BALI, and a score combining both, using a logistic regression model, were assessed.

RESULTS

The MTAS and BALI scores were closely correlated (r(2) > 0.56); each differed between the diagnostic groups. Having an unfavorable MTAS score was associated with an increased risk of MCI-AD conversion (OR = 3.71, p = 0.039), adjusted for age, sex, and education; having an unfavorable BALI score marginally contributed to such risks (OR = 4.08, p = 0.080). Combining MTAS and BALI components resulted in a greater OR (8.99, p = 0.007) and an improved predictive accuracy (75.9%, p = 0.002).

CONCLUSION

Multiple structural changes have an additive effect on AD. The data support potential future roles of combining multiple coexisting structural changes to benefit AD diagnosis, progression monitoring, and/or treatment effect evaluation.

Evolution of the diagnostic criteria for degenerative and cognitive disorders

PURPOSE OF REVIEW

This review describes the evolution of the clinical criteria for Alzheimer's disease over the past 25 years, with special emphasis on those recently published that have incorporated the use of biomarkers.

RECENT FINDINGS

One of the most important advances in the knowledge of Alzheimer's disease was the development of cerebrospinal fluid, PET and MRI biomarkers. These have shown that the Alzheimer's disease is present in cognitively normal individuals, suggesting that there is a long incubation process that precedes the onset of the symptoms. Although there are diagnostic criteria for Alzheimer's disease, the National Institute on Aging and the Alzheimer's Association has proposed a set of diagnostic criteria oriented to provide a unified vision of the pathological process from preclinical, to mild cognitive impairment, and to full-blown dementia. These new criteria take advantage of different biomarkers to support the clinical diagnosis of the different stages of the disease.

SUMMARY

The new guidelines provide a definition of the dementia syndrome and core diagnostic features to be used in research and clinical practice, although they caution about the use of biomarkers, since they still require validation, and the longitudinal interaction and dynamics of these biomarkers in relationship to the manifestation of the symptoms are not fully understood.

Volumetric and visual rating of magnetic resonance imaging scans in the diagnosis of amnestic mild cognitive impairment and Alzheimer's disease

BACKGROUND

In the diagnosis of Alzheimer's disease (AD), structural magnetic resonance imaging (MRI) scans have been used primarily to exclude non-Alzheimer's causes of dementia. However, the pattern and the extent of medial temporal atrophy on structural MRI scans, which correlate strongly with the pathological severity of AD, can be used to support the diagnosis of a degenerative dementia, especially AD, even in its early predementia stage.

METHODS

Elderly subjects (n = 224) were diagnosed with either no cognitive impairment (NCI), amnestic mild cognitive impairment (aMCI), or AD. Hippocampal and hemispheric gray matter volumes were measured on structural MRI scans, and a new visual rating system was used to score the severity of medial temporal atrophy (VRS-MTA) of the hippocampus (HPC), entorhinal cortex, and perirhinal cortex on a coronal image intersecting the mammillary bodies.

RESULTS

Although both VRS-MTA scores and HPC volumes distinguished between subjects with NCI, aMCI, and AD, subjects with aMCI and NCI could be better distinguished using right VRS-MTA scores, in comparison with right HPC volumes. VRS-MTA scores were more highly correlated with episodic memory and Clinical Dementia Rating scores. A combination of left sided VRS-MTA scores and left sided hippocampal volume was the most predictive measure of diagnostic classification.

CONCLUSION

VRS-MTA is a clinically convenient method or distinguishing aMCI or AD from NCI. As compared with volumetric measures, it provides better discriminatory power and correlates more strongly with memory and functional scores.