Characteristics of mild cognitive impairment tending to convert into Alzheimer's disease or dementia with Lewy bodies: A follow-up study in a memory clinic

Characteristics of amnestic patients with hypometabolism patterns suggestive of Lewy body pathology

A clinical diagnosis of Alzheimer's disease dementia (ADD) encompasses considerable pathological and clinical heterogeneity. While Alzheimer's disease patients typically show a characteristic temporo-parietal pattern of glucose hypometabolism on 18F-fluorodeoxyglucose (FDG)-PET imaging, previous studies have identified a subset of patients showing a distinct posterior-occipital hypometabolism pattern associated with Lewy body pathology. Here, we aimed to improve the understanding of the clinical relevance of these posterior-occipital FDG-PET patterns in patients with Alzheimer's disease-like amnestic presentations. Our study included 1214 patients with clinical diagnoses of ADD (n = 305) or amnestic mild cognitive impairment (aMCI, n = 909) from the Alzheimer's Disease Neuroimaging Initiative, who had FDG-PET scans available. Individual FDG-PET scans were classified as being suggestive of Alzheimer's (AD-like) or Lewy body (LB-like) pathology by using a logistic regression classifier trained on a separate set of patients with autopsy-confirmed Alzheimer's disease or Lewy body pathology. AD- and LB-like subgroups were compared on amyloid-β and tau-PET, domain-specific cognitive profiles (memory versus executive function performance), as well as the presence of hallucinations and their evolution over follow-up (≈6 years for aMCI, ≈3 years for ADD). Around 12% of the aMCI and ADD patients were classified as LB-like. For both aMCI and ADD patients, the LB-like group showed significantly lower regional tau-PET burden than the AD-like subgroup, but amyloid-β load was only significantly lower in the aMCI LB-like subgroup. LB- and AD-like subgroups did not significantly differ in global cognition (aMCI: d = 0.15, P = 0.16; ADD: d = 0.02, P = 0.90), but LB-like patients exhibited a more dysexecutive cognitive profile relative to the memory deficit (aMCI: d = 0.35, P = 0.01; ADD: d = 0.85 P < 0.001), and had a significantly higher risk of developing hallucinations over follow-up [aMCI: hazard ratio = 1.8, 95% confidence interval = (1.29, 3.04), P = 0.02; ADD: hazard ratio = 2.2, 95% confidence interval = (1.53, 4.06) P = 0.01]. In summary, a sizeable group of clinically diagnosed ADD and aMCI patients exhibit posterior-occipital FDG-PET patterns typically associated with Lewy body pathology, and these also show less abnormal Alzheimer's disease biomarkers as well as specific clinical features typically associated with dementia with Lewy bodies.

Research diagnostic criteria for mild cognitive impairment with Lewy bodies: A systematic review and meta-analysis

INTRODUCTION

Operationalized research criteria for mild cognitive impairment with Lewy bodies (MCI-LB) were published in 2020. The aim of this systematic review and meta-analysis was to review the evidence for the diagnostic clinical features and biomarkers in MCI-LB set out in the criteria.

METHODS

MEDLINE, PubMed, and Embase were searched on 9/28/22 for relevant articles. Articles were included if they presented original data reporting the rates of diagnostic features in MCI-LB.

RESULTS

Fifty-seven articles were included. The meta-analysis supported the inclusion of the current clinical features in the diagnostic criteria. Evidence for striatal dopaminergic imaging and meta-iodobenzylguanidine cardiac scintigraphy, though limited, supports their inclusion. Quantitative electroencephalogram (EEG) and fluorodeoxyglucose positron emission tomography (PET) show promise as diagnostic biomarkers.

DISCUSSION

The available evidence largely supports the current diagnostic criteria for MCI-LB. Further evidence will help refine the diagnostic criteria and understand how best to apply them in clinical practice and research.

HIGHLIGHTS

A meta-analysis of the diagnostic features of MCI-LB was carried out. The four core clinical features were more common in MCI-LB than MCI-AD/stable MCI. Neuropsychiatric and autonomic features were also more common in MCI-LB. More evidence is needed for the proposed biomarkers. FDG-PET and quantitative EEG show promise as diagnostic biomarkers in MCI-LB.

Brain 18 F-FDG-PET and an optimized cingulate island ratio to differentiate Lewy body dementia and Alzheimer's disease

BACKGROUND AND PURPOSE

The diagnosis of Dementia with Lewy Bodies (DLB) is challenging due to various clinical presentations and clinical and neuropathological features that overlap with Alzheimer's disease (AD). The use of ¹⁸ F-Fluorodeoxyglucose-PET (¹⁸ F-FDG-PET) can be limited due to similar patterns in DLB and AD. However, metabolism in the posterior cingulate cortex is known to be relatively preserved in DLB and visual assessment of the "cingulate island sign" became a helpful tool in the analysis of 18F-FDG-PET. The aim of this study was the evaluation of visual and semiquantitative 18F-FDG-PET analyses in the diagnosis of DLB and the differentiation to AD as well as its relation to other dementia biomarkers.

METHODS

This retrospective study comprises 81 patients with a clinical diagnosis of DLB or AD that underwent ¹⁸ F-FDG-PET/CT. PET scans were analyzed visually and semiquantitatively and results were compared to clinical data, cerebrospinal fluid results, dopamine transporter scintigraphy, and 18F-Florbetaben-PET. Furthermore, different cingulate island ratios were calculated to analyze their diagnostic accuracy.

RESULTS

Visual assessment of 18F-FDG-PET showed an accuracy of 62%-77% in differentiating between DLB and AD. Standard uptake values were significantly lower in the primary visual cortex and the lateral occipital cortex of DLB patients compared to AD patients. The cingulate island ratio was significantly higher in the DLB group compared to the AD group and the ratio posterior cingulate cortex to visual cortex plus lateral occipital cortex showed the highest diagnostic accuracy to discriminate between DLB and AD at 81%.

CONCLUSIONS

Semiquantitative 18F-FDG-PET imaging and especially the use of an optimized cingulate island ratio are valuable tools to differentiate between DLB and AD.

Correlates of Conversion from Mild Cognitive Impairment to Dementia with Lewy Bodies: Data from the National Alzheimer's Coordinating Center

BACKGROUND

Many patients with dementia with Lewy bodies (DLB) miss out on the best standards of care and psychosocial support due to diagnostic delays or inaccuracies following symptom onset.

OBJECTIVE

This study seeks to identify baseline characteristics in individuals with mild cognitive impairment (MCI) that correlate with eventual conversion to DLB or Alzheimer's disease (AD).

METHODS

Baseline neuropsychological and neuropsychiatric data were analyzed in National Alzheimer's Coordinating Center participants who completed the Uniform Data Set between 2006 and 2020 and subsequently converted from MCI to DLB or AD (n = 1632).

RESULTS

Only 6% of participants with MCI converted to DLB. Among those who converted to DLB, multidomain amnestic MCI (aMCI) was the most common subtype at study entry. As part of logistic regression analyses, odds ratios (ORs) were estimated for conversion to DLB versus AD based on study-entry characteristics, adjusting for age, sex, education, and years to diagnosis. The strongest predictors of conversion to DLB (p≤0.0001) were nonamnestic MCI versus aMCI (OR 8.2, CI [5.0, 14]), multidomain MCI versus single-domain MCI (OR 2.7, CI [1.7. 4.2]), male sex (OR 4.2, CI [2.5, 7.1]), and presence of nighttime behaviors (OR 4.4 CI [2.8, 6.9]).

CONCLUSION

A diagnosis of prodromal DLB should be considered in individuals with MCI who present with prominent executive/visuospatial deficits, neuropsychiatric symptoms, and less memory impairment. Early diagnosis of DLB may guide treatment planning, including the avoidance of antipsychotic medications in patients who develop psychotic symptoms, caregiver support, and initiation of early treatment(s) once medications become available.

"2-step MCI-AD": a simple scoring system to predict rapid conversion from mild cognitive impairment to Alzheimer dementia

BACKGROUND

Several techniques are available to identify, among patients with mild cognitive impairment (MCI), those at risk of conversion to Alzheimer dementia (CAD). However, simple cost-effective methods to assess the risk are not available yet.

METHODS

This retrospective study included 143 MCI outpatients (76.6±5.2 years, 46.8% women). Baseline variables were common neuropsychological tests (including Mini Mental State Examination-MMSE and Montreal Cognitive Assessment-MoCA), brain CT and 18F-fluorodeoxyglucose (FDG)-PET. Outcome variable was CAD after 1 year.

RESULTS

At follow-up, 31 (21.7%) patients had CAD. In multivariable analysis (OR, 95% CI), female sex (4.7, 1.6-14.0), MoCA-executive component <3 (6.3, 2.1-19.2), left medial temporal atrophy (MTA) ≥3 (5.4, 1.9-15.7) and FDG-PET suggesting CAD (5.4, 1.9-15.7) were associated with CAD (area under ROC curve 0.873). Without FDG-PET, MMSE score <28 remained associated with CAD (6.0, 2.2-16.9). As first step (before FDG-PET execution), we counted 1 point for MMSE <28, executive MoCA <3 and left MTA ≥3. With 2-3 points CAD probability was high (75%) and with 0 points it was low (6.5%). Thus, FDG-PET (second step) might be performed only in patients with 1 point (probability 19.7%, 42.7% of patients). Among them, 35% had a positive FDG-PET, suggesting high risk. Overall, 28.0% of patients were considered at high risk (specificity 83.9%, sensitivity 71.0%, accuracy 81.1%).

CONCLUSION

With a 2-step procedure, less than half of MCI patients might undergo FDG-PET and nearly a quarter of our patients was found to be at high CAD risk, including almost three quarters of future CADs.

Research criteria for the diagnosis of prodromal dementia with Lewy bodies

The prodromal phase of dementia with Lewy bodies (DLB) includes (1) mild cognitive impairment (MCI), (2) delirium-onset, and (3) psychiatric-onset presentations. The purpose of our review is to determine whether there is sufficient information yet available to justify development of diagnostic criteria for each of these. Our goal is to achieve evidence-based recommendations for the recognition of DLB at a predementia, symptomatic stage. We propose operationalized diagnostic criteria for probable and possible mild cognitive impairment with Lewy bodies, which are intended for use in research settings pending validation for use in clinical practice. They are compatible with current criteria for other prodromal neurodegenerative disorders including Alzheimer and Parkinson disease. Although there is still insufficient evidence to propose formal criteria for delirium-onset and psychiatric-onset presentations of DLB, we feel that it is important to characterize them, raising the index of diagnostic suspicion and prioritizing them for further investigation.

Plasma Transthyretin as a Predictor of Amnestic Mild Cognitive Impairment Conversion to Dementia

Amnestic mild cognitive impairment (MCI) is a prodromal stage of dementia, with a higher incidence of these patients progressing to Alzheimer’s disease (AD) than normal aging people. A biomarker for the early detection and prediction for this progression is important. We recruited MCI subjects in three teaching hospitals and conducted longitudinal follow-up for 5 years at one-year intervals. Cognitively healthy controls were recruited for comparisom at baseline. Plasma transthyretin (TTR) levels were measured by ELISA. Survival analysis with time to AD conversion as an outcome variable was calculated with the multivariable Cox proportional hazards models using TTR as a continuous variable with adjustment for other covariates and bootstrapping resampling analysis. In total, 184 MCI subjects and 40 sex- and age-matched controls were recruited at baseline. At baseline, MCI patients had higher TTR levels compared with the control group. During the longitudinal follow-ups, 135 MCI patients (73.4%) completed follow-up at least once. The TTR level was an independent predictor for MCI conversion to AD when using TTR as a continuous variable (p = 0.023, 95% CI 1.001–1.007). In addition, in MCI converters, the TTR level at the point when they converted to AD was significantly lower than that at baseline (328.6 ± 66.5 vs. 381.9 ± 77.6 ug/ml, p < 0.001). Our study demonstrates the temporal relationship between the plasma TTR level and the conversion from MCI to AD.

Qualitative Scoring of the Pentagon Test: A Tool for the Identification of Subtle Cognitive Deficits in Isolated REM Sleep Behavior Disorder Patients

OBJECTIVE

Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) frequently represents the prodromal stage of alpha-synucleinopathies, and similar to these pathologies, iRBD patients show neuropsychological deficits, particularly in the domain of visuospatial abilities and executive functions. We hypothesized that the qualitative scoring of the Mini-Mental State Examination pentagon test (QSPT) may detect subtle visuospatial deficits in these subjects, and we evaluated its relationship with indexes of sleep quality, as measured by polysomnography.

METHODS

A total of 80 polysomnography-confirmed iRBD patients and 40 healthy controls (HCs) were retrospectively recruited. Global and specific qualitative performances were evaluated according to QSPT procedure. Comparisons between iRBD and HC regarding all QSPT parameters, neuropsychological tests, and polysomnographic recordings were performed.

RESULTS

Patients displayed significantly lower scores in both "closing-in" and total score parameters in comparison to HC. The QSPT total score exhibited significant positive correlations with verbal comprehension, fluency, visuospatial abilities, and executive functions. Notably, iRBD patients with impaired performance at QSPT showed decreased neuropsychological performances and higher percentages of slow wave sleep (SWS). In addition, SWS percentages negatively correlated with verbal comprehension, fluency, visuospatial abilities, executive functions, and QSPT total score.

CONCLUSION

QSPT may represent a brief and easy to administer tool for the detection of subtle visuospatial changes in iRBD patients. Furthermore, polysomnographic findings suggest a possible slowdown of electroencephalographic pattern during non-REM sleep in iRBD patients in line with the presence of cognitive decline.

The Cingulate Island Sign on FDG-PET vs. IMP-SPECT to Assess Mild Cognitive Impairment in Alzheimer's Disease vs. Dementia with Lewy Bodies

BACKGROUND AND PURPOSE

The cingulate island sign (CIS) on ¹⁸ F-fluorodeoxyglucose positron emission tomography (FDG-PET); ie, the relative preservation of mid-posterior cingulate cortex metabolism, is a supportive biomarker in the diagnostic criteria for dementia with Lewy bodies (DLB). However, limited information is currently available on the diagnostic value of the CIS on FDG-PET or ¹²³ I-iodoamphetamine single-photon emission computed tomography (IMP-SPECT) for differentiating between mild cognitive impairment (MCI) due to Alzheimer's disease (AD) (MCI-AD) and MCI due to DLB (MCI-DLB).

METHODS

We examined the CIS ratio in 9 AD patients, 9 DLB patients, 8 patients with MCI-AD, and 9 patients with MCI-DLB using FDG-PET and IMP-SPECT. The CIS ratio was calculated using NEUROSTAT software.

RESULTS

In the dementia groups, a receiver operating characteristic analysis of the CIS ratio showed significant accuracy for differentiating between AD and DLB on FDG-PET and IMP-SPECT. In the MCI groups, only the FDG-PET derived CIS ratio displayed significant accuracy for differentiating between AD and DLB.

CONCLUSIONS

The FDG-PET and IMP-SPECT derived CIS ratios are both useful for differentiating between AD and DLB. The FDG-PET derived CIS ratio is more valuable than the IMP-SPECT derived CIS ratio for differential diagnosis in patients with MCI. A larger study is needed to confirm these results.

Imaging in prodromal dementia with Lewy bodies: Where do we stand?

OBJECTIVES

The aim of this review was to provide an overview of the literature on imaging in prodromal dementia with Lewy bodies (DLB).

DESIGN

Systematic PubMed search and literature review.

RESULTS

Diagnostic classification of the prodromal DLB stage remains to be established but is likely to require imaging biomarkers to improve diagnostic accuracy. In subjects with mild cognitive impairment with Lewy body disease (MCI-LB) (here synonymous with prodromal DLB) and REM sleep behaviour disorder, a high risk condition for future conversion to a synucleinopathy, imaging modalities have assessed early structural brain changes, striatal dopaminergic integrity, metabolic brain, and cerebral perfusion alterations. It remains uncertain whether structural brain imaging can differentiate MCI-LB from mild cognitive impairment with Alzheimer disease (MCI-AD), but early right anterior insula thinning has been reported to occur in MCI-LB compared with MCI-AD. Dopaminergic deficits have been observed in a substantial proportion of MCI-LB subjects and have a high specificity for Lewy body disease at the pre-dementia stage. Cardiac sympathetic denervation, occipital hypometabolism, or hypoperfusion is less studied as this pre-dementia stage and it remains to be determined whether any imaging abnormalities antedate DLB.

CONCLUSION

Imaging studies in prodromal DLB are still in their infancy but offer great potential to study early in vivo structural and functional biological alterations. Future work should focus on longitudinal multimodal imaging studies with postmortem validation of diagnosis in order to develop and then validate criteria for prodromal DLB.