Application of the VSRAD, a specific and sensitive voxel-based morphometry, to comparison of entorhinal cortex atrophy between dementia with Lewy bodies and Alzheimer's disease

Comparing Medial Temporal Atrophy Between Early-Onset Semantic Dementia and Early-Onset Alzheimer's Disease Using Voxel-Based Morphometry: A Multicenter MRI Study

BACKGROUND

Early-onset Semantic dementia (EOSD) and early-onset Alzheimer's disease (EOAD) are often difficult to clinically differentiate in the early stages of the diseases because of the overlaps of clinical symptoms such as language symptoms. We compared the degree of atrophy in medial temporal structures between the two types of dementia using the voxel-based specific regional analysis system for Alzheimer's disease (VSRAD).

METHODS

The participants included 29 (age: 61.7±4.5 years) and 39 (age: 60.2±4.9 years) patients with EOSD and EOAD, respectively. The degree of atrophy in medial temporal structures was quantified using the VSRAD for magnetic resonance imaging data. Receiver operating characteristic (ROC) analysis was performed to distinguish patients with EOSD and EOAD using the mean Z score (Z-score) in bilateral medial temporal structures and the absolute value (laterality score) of the laterality of Z-score (| right-left |) for indicating the degree of asymmetrical atrophy in medial temporal structures.

RESULTS

The EOSD group had significantly higher Z and laterality scores than the EOAD group (Zscores: mean ± standard deviation: 3.74±1.05 vs. 1.56±0.81, respectively; P<0.001; laterality score: mean ± standard deviation: 2.35±1.23 vs. 0.68±0.51, respectively; P<0.001). In ROC analysis, the sensitivity and specificity to differentiate EOSD from EOAD by a Z-score of 2.29 were 97% and 85%, respectively and by the laterality score of 1.05 were 93% and 85%, respectively.

CONCLUSION

EOSD leads to more severe and asymmetrical atrophy in medial temporal structures than EOAD. The VSRAD may be useful to distinguish between these dementias that have several clinically similar symptoms.

Lewy Body Dementias: A Coin with Two Sides?

Lewy body dementias (LBDs) consist of dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), which are clinically similar syndromes that share neuropathological findings with widespread cortical Lewy body deposition, often with a variable degree of concomitant Alzheimer pathology. The objective of this article is to provide an overview of the neuropathological and clinical features, current diagnostic criteria, biomarkers, and management of LBD. Literature research was performed using the PubMed database, and the most pertinent articles were read and are discussed in this paper. The diagnostic criteria for DLB have recently been updated, with the addition of indicative and supportive biomarker information. The time interval of dementia onset relative to parkinsonism remains the major distinction between DLB and PDD, underpinning controversy about whether they are the same illness in a different spectrum of the disease or two separate neurodegenerative disorders. The treatment for LBD is only symptomatic, but the expected progression and prognosis differ between the two entities. Diagnosis in prodromal stages should be of the utmost importance, because implementing early treatment might change the course of the illness if disease-modifying therapies are developed in the future. Thus, the identification of novel biomarkers constitutes an area of active research, with a special focus on α-synuclein markers.

The development of new method to differentiate between Dementia with Lewy bodies and Alzheimer's disease by cerebral perfusion SPECT-comparison to CIScore

PURPOSE

The Cingulate Island Sign score (CIScore) by rCBF SPECT is used in the differentiation between Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) but has some false-positive AD cases. To resolve the problem, we developed new differential diagnosing method incorporating occipital lobe and para-hippocampal rCBF.

MATERIALS AND METHODS

In 27 DLB and 31 AD cases undertaken Tc-99 m-ECD SPECT, we evaluated the mean Z score in the bilateral superior, middle, inferior occipital gyri, cuneus, amygdala, hippocampus, and para-hippocampus. One criterion of DLB was defined as the case with CIScore lower than 0.27. The other criteria were the cases of following either or both two conditions were satisfied. (1) The number of occipital gyri with mean Z score higher than 1 is three or more. (2) The number of hippocampal regions with mean Z score higher than 1 is one or less. We compared the differential diagnostic ability among these four criterions.

RESULTS

The diagnostic accuracy by CIscore was 69% and that of the occipital gyri analysis 84%, para-hippocampal regions analysis 76% and combined occipital gyri and para-hippocampal regions analysis 93%.

CONCLUSION

The new method by combined rCBF analysis of occipital gyri and para-hippocampal regions showed best diagnostic ability in differentiating DLB from AD.

Structural and Functional Magnetic Resonance Imaging of Dementia With Lewy Bodies

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia after Alzheimer's disease (AD). Although diagnosis may be challenging, there is increasing evidence that the use of biomarkers according to 2017 revised criteria for diagnosis and management of dementia with Lewy bodies can increase diagnostic accuracy. Apart from nuclear medicine techniques, various magnetic resonance imaging (MRI) techniques have been utilized in attempt to enhance diagnostic accuracy. This chapter reviews structural, functional and diffusion MRI studies in DLB cohorts being compared to healthy controls, AD or dementia in Parkinson's disease (PDD). We also included relatively new MRI methods that may have potential to identify early DLB subjects and aim at examining brain iron and neuromelanin.

Ser46-Phosphorylated MARCKS Is a Marker of Neurite Degeneration at the Pre-aggregation Stage in PD/DLB Pathology

Phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) reflects neurite degeneration at the early stage of Alzheimer’s disease (AD), before extracellular Aβ aggregates are histologically detectable. Here, we demonstrate that similar changes in MARCKS occur in Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) pathologies in both mouse models and human patients. The increase in the level of pSer46-MARCKS began before α-synuclein aggregate formation, at a time when human α-Syn-BAC-Tg/GBA-hetero-KO mice exhibited no symptoms, and was sustained during aging, consistent with the pattern in human postmortem brains. The results strongly imply a common mechanism of pre-aggregation neurite degeneration in AD and PD/DLB pathologies.

Decreased N-Acetyl Aspartate/Myo-Inositol Ratio in the Posterior Cingulate Cortex Shown by Magnetic Resonance Spectroscopy May Be One of the Risk Markers of Preclinical Alzheimer's Disease: A 7-Year Follow-Up Study

Although molecular positron emission tomography imaging of amyloid and tau proteins can facilitate the detection of preclinical Alzheimer’s disease (AD) pathology, it is not useful in clinical practice. More practical surrogate markers for preclinical AD would provide valuable tools. Thus, we sought to validate the utility of conventional magnetic resonance spectroscopy (MRS) as a screening method for preclinical AD. A total of 289 older participants who were cognitively normal at baseline were clinically followed up for analysis of MRS metabolites, including N-acetyl aspartate (NAA) and myo-inositol (MI) in the posterior cingulate cortex (PCC) for 7 years. The 289 participants were retrospectively divided into five groups 7 years after baseline: 200 (69%) remained cognitively normal; 53 (18%) developed mild cognitive impairment (MCI); 21 (7%) developed AD; eight (2%) developed Parkinson’s disease with normal cognition, and seven (2%) developed dementia with Lewy bodies (DLB). The NAA/MI ratios of the PCC in the AD, MCI, and DLB groups were significantly decreased compared with participants who maintained normal cognition from baseline to 7 years after baseline. MMSE scores 7 years after baseline were significantly correlated with MI/Cr and NAA/MI ratios in the PCC. These results suggest that cognitively normal elderly subjects with low NAA/MI ratios in the PCC might be at risk of progression to clinical AD. Thus, the NAA/MI ratio in the PCC measured with conventional ¹H MRS should be reconsidered as a possible adjunctive screening marker of preclinical AD in clinical practice.

Neuroimaging in Lewy body dementia

Lewy body dementia (DLB) is a common form of cognitive impairment, accounting for 30% of dementia cases in ages over 65 years. Early diagnosis of DLB has been challenging; particularly in the context of differentiation with Parkinson’s disease dementia and other forms of dementias, such as Alzheimer’s disease and rapidly progressive dementias. Current practice involves the use of [¹²³I]FP-CIT-SPECT, [¹⁸F]FDG PET and [¹²³I]MIBG molecular imaging to support diagnostic procedures. Structural imaging techniques have an essential role for excluding structural causes, which could lead to a DLB-like phenotype, as well as aiding differential diagnosis through illustrating disease-specific patterns of atrophy. Novel PET molecular imaging modalities, such as amyloid and tau imaging, may provide further insights into DLB pathophysiology and may aid in early diagnosis. A multimodal approach, through combining various established techniques and possibly using novel radioligands, might further aid towards an in-depth understanding of this highly disabling disease. In this review, we will provide an overview of neuroimaging applications in patients with DLB.

Entorhinal cortex: a good biomarker of mild cognitive impairment and mild Alzheimer's disease

Entorhinal cortex (EC), thought to be the location of the earliest lesions in Alzheimer's disease (AD), has been widely studied in recent years. With the irreversible pathological changes of AD, there is an urgent need to find biomarkers that can be used to predict the presence of the disease before it is clinically expressed. The aim of this review is to summarize and analyze recent findings that are relevant to the important role of EC in the diagnosis of mild cognitive impairment (MCI) and mild AD and to describe a range of neuroimaging techniques used to define the EC boundary. A comprehensive literature search for articles published up to May 2015 was performed. Our research highlights the finding that atrophy in EC reflects the early pathological changes of AD and can be a strong predictor of prodromal AD. The early changes in EC are a good imaging biomarker that can be used to discriminate individuals with MCI from normal control subjects. A larger degree of atrophy in EC predicts increased disease severity, and the right EC in patients with mild AD exhibited greater changes than the left side. In addition, the EC seems to have an obvious advantage over the hippocampus as a biomarker when predicting future conversion to AD in individuals with MCI, and it may be of help in following the course of disease progression. In this review, we also summarize the main differences observed between the hippocampus and the EC when differentiating diseases. These findings will hopefully provide an opportunity for the effective prevention and early treatment of AD.

Cingulate island sign on FDG-PET is associated with medial temporal lobe atrophy in dementia with Lewy bodies

OBJECTIVE

The cingulate island sign (CIS), which refers to sparing of the posterior cingulate relative to the precuneus and cuneus, has been proposed as an FDG-PET imaging feature of dementia with Lewy bodies (DLB). The sign is reportedly associated with Alzheimer's disease (AD) type neurofibrillary tangle (NFT) pathology in autopsy cases. To confirm this relationship using neuroimaging modalities in vivo, we investigated associations between CIS and the medial temporal lobe (MTL) atrophy in DLB.

METHODS

Twenty-four patients each of DLB and AD underwent both (18)F-FDG-PET and MRI with voxel-based morphometry. Dopamine transporter (DAT) density was also measured by DAT-SPECT in all those with DLB and in five with AD. The accumulation of FDG in the posterior cingulate ROI was divided by that in the precuneus plus cuneus ROI to derive the CIS ratio from the FDG-PET images. Values for cognitive function of Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Ray Auditory Verbal Learning Test (RAVLT) and scores for the core-feature triad of fluctuation, hallucination and parkinsonism were also statistically analyzed.

RESULTS

The CIS ratio was higher in DLB than in AD (p < 0.001). The degree of MTL atrophy was lower in DLB than in AD (p < 0.001). The CIS ratio and the degree of MTL atrophy were inversely correlated with DLB (p < 0.001) and with AD (p < 0.05). The CIS ratio did not significantly correlate with DAT density in DLB or with MMSE, FAB, fluctuation score and parkinsonism score. However, the CIS ratio significantly correlated with RAVLT and hallucination scores (both, p < 0.05).

CONCLUSIONS

The CIS on FDG-PET in DLB was associated with MTL atrophy but not with striatal DAT density, suggesting that the CIS is a useful neuroimaging biomarker to evaluate coexisting AD-type NFT pathology in vivo. The CIS was also associated with memory impairment and visual hallucination in DLB.

The Relationship Between Medial Temporal Lobe Atrophy and Cognitive Impairment in Patients With Dementia With Lewy Bodies

BACKGROUND

The relationship between medial temporal lobe atrophy (MTA) and cognitive impairment in patients with dementia with Lewy bodies (DLB) remains unclear. We examined this relationship using voxel-based specific regional analysis system for Alzheimer disease (VSRAD) advance software, which allowed us to quantify the degree of MTA on images obtained from magnetic resonance imaging (MRI) scans.

METHODS

Thirty-seven patients diagnosed with DLB were recruited and scanned with a 1.5 Tesla MRI scanner. All MRI data were analyzed using VSRAD advance. The target volume of interest (VOI) included the entire region of the entorhinal cortex, hippocampus, and amygdala. The degree of MTA was obtained from the averaged positive z-score (Z score) on the target VOI, with higher scores indicating more severe MTA. Mini-Mental State Examination (MMSE) and the Revised Hasegawa Dementia Scale (HDS-R), which strengthened the measures of memory and language more than MMSE, were used to assess the presence of cognitive impairment.

RESULTS

A negative correlation was found between the Z score and MMSE total scores or the HDS-R total scores. A stepwise multiple regression analysis performed to adjust the covariate effects of sex, age, the onset age of the disease, duration of DLB, years of education, and donepezil treatment showed that the HDS-R total scores were independently associated with the Z score, whereas MMSE total scores were not.

CONCLUSIONS

These results suggest that MTA is related to cognitive impairment in patients with DLB, particularly the regions of orientation, immediate and delayed recall, and word fluency.

The potentially protective effect of donepezil in Alzheimer's disease

BACKGROUND/AIMS

Donepezil is an acetylcholinesterase inhibitor used to treat Alzheimer's disease (AD). In this study, we used a voxel-based specific regional analysis system for AD (VSRAD) to analyze the hippocampal volume and to assess the pharmacologic effects of donepezil as a disease modifier.

METHODS

A total of 185 AD patients underwent MRI, 120 (43 men and 77 women, 77.8 ± 7.1 years) without and 65 (29 men and 36 women, 78.4 ± 6.0 years) with donepezil treatment. VSRAD was compared in both groups and against a database of 80 normal subjects. The Z-score was used to assess the degree of hippocampal atrophy.

RESULTS

No significant difference between the groups was found for age, sex, or Z-scores, but a significant difference was found for mean Mini-Mental State Examination (MMSE) scores (p = 0.02, Student's t test). Single regression analysis showed no significant association between Z-scores and MMSE scores in the treated group (p = 0.494), but a significant association in the untreated group (p = 0.001) was observed. This implies that the MMSE score becomes lower when the Z-score is higher in the untreated group, whereas there is no significant trend in the treated group.

CONCLUSION

Donepezil affects the relationship between hippocampal volume and cognitive function and may therefore have a pharmacologic effect as a disease modifier.

Non-Alzheimer's disease-related memory impairment and dementia

Although Alzheimer's disease (AD) is a common cause of memory impairment and dementia in the elderly disturbed memory function is a widespread subjective and/or objective symptom in a variety of medical conditions. The early detection and correct distinction of AD from non-AD memory impairment is critically important to detect possibly treatable and reversible underlying causes. In the context of clinical research, it is crucial to correctly distinguish between AD or non-AD memory impairment in order to build homogenous study populations for the assessment of new therapeutic possibilities. The distinction of AD from non-AD memory impairment may be difficult, especially in mildly affected patients, due to an overlap of clinical symptoms and biomarker alterations between AD and certain non-AD conditions. This review aims to describe recent aspects of the differential diagnosis of AD and non-AD related memory impairment and how these may be considered in the presence of memory deficits.

Neuroimaging characteristics of dementia with Lewy bodies

This review summarises the findings and applications from neuroimaging studies in dementia with Lewy bodies (DLB), highlighting key differences between DLB and other subtypes of dementia. We also discuss the increasingly important role of imaging biomarkers in differential diagnosis and outline promising areas for future research in DLB. DLB shares common clinical, neuropsychological and pathological features with Parkinson’s disease dementia and other dementia subtypes, such as Alzheimer’s disease. Despite the development of consensus diagnostic criteria, the sensitivity for differential diagnosis of DLB in clinical practice remains low and many DLB patients will be misdiagnosed. The importance of developing accurate imaging markers in dementia is highlighted by the potential for treatments targeting specific molecular abnormalities as well as the responsiveness to cholinesterase inhibitors and marked neuroleptic sensitivity of DLB. We review various brain imaging techniques that have been applied to investigate DLB, including the characteristic nigrostriatal degeneration in DLB using positron emission tomography (PET) and single-photon emission computed tomography (SPECT) tracers. Dopamine transporter loss has proven to reliably differentiate DLB from other dementias and has been incorporated into the revised clinical diagnostic criteria for DLB. To date, this remains the 'gold standard' for diagnostic imaging of DLB. Regional cerebral blood flow, 18 F-fluorodeoxygluclose-PET and SPECT have also identified marked deficits in the occipital regions with relative sparing of the medial temporal lobe when compared to Alzheimer’s disease. In addition, structural, diffusion, and functional magnetic resonance imaging techniques have shown alterations in structure, white matter integrity, and functional activity in DLB. We argue that the multimodal identification of DLB-specific biomarkers has the potential to improve ante-mortem diagnosis and contribute to our understanding of the pathological background of DLB and its progression.