Memory markers in the continuum of the Alzheimer's clinical syndrome

Anterior-temporal hippocampal network mechanisms of left angular gyrus-navigated rTMS for memory improvement in aMCI: A sham-controlled study

INTRODUCTION

Neuro-navigated repetitive transcranial magnetic stimulation (rTMS) of the left angular gyrus has been broadly investigated for the treatment of amnestic mild cognitive impairment (aMCI). Although abnormalities in two hippocampal networks, the anterior-temporal (AT) and posterior-medial (PM) networks, are consistent with aMCI and are potential therapeutic targets for rTMS, the underlying mechanisms of the therapeutic effects of rTMS on hippocampal network connections remain unknown. Here, we assessed the impact of left angular gyrus rTMS on activity in these networks and explored whether the treatment response was due to the distance between the clinically applied target (the group average optimal site) and the personalized target in patients with aMCI.

METHODS

Sixty subjects clinically diagnosed with aMCI participated in this study after 20 sessions of sham-controlled rTMS targeting the left angular gyrus. Resting-state functional magnetic resonance imaging and neuropsychological assessments were performed before and after rTMS. Functional connectivity alterations in the PM and AT networks were assessed using seed-based functional connectivity analysis and two-factor repeated measures analysis of variance (ANOVA). We then computed the correlations between the functional connectivity changes and clinical rating scales. Finally, we examined whether the Euclidean distance between the clinically applied and personalized targets predicted the subsequent treatment response.

RESULTS

Compared with the sham group, the active rTMS group showed rTMS-induced deactivation of functional connectivity within the medial temporal lobe-AT network, with a negative correlation with episodic memory score changes. Moreover, the active rTMS lowers the interdependency of changes in the PM and AT networks. Finally, the Euclidean distance between the clinically applied and personalized target distances could predict subsequent network lever responses in the active rTMS group.

CONCLUSIONS

Neuro-navigated rTMS selectively modulates widespread functional connectivity abnormalities in the PM and AT hippocampal networks in aMCI patients, and the modulation of hippocampal-AT network connectivity can efficiently reverse memory deficits. The results also highlight the necessity of personalized targets for fMRI.

Consensus on rapid screening for prodromal Alzheimer's disease in China

Alzheimer's disease (AD) is a common cause of dementia, characterised by cerebral amyloid-β deposition, pathological tau and neurodegeneration. The prodromal stage of AD (pAD) refers to patients with mild cognitive impairment (MCI) and evidence of AD's pathology. At this stage, disease-modifying interventions should be used to prevent the progression to dementia. Given the inherent heterogeneity of MCI, more specific biomarkers are needed to elucidate the underlying AD's pathology. Although the uses of cerebrospinal fluid and positron emission tomography are widely accepted methods for detecting AD's pathology, their clinical applications are limited by their high costs and invasiveness, particularly in low-income areas in China. Therefore, to improve the early detection of Alzheimer's disease (AD) pathology through cost-effective screening methods, a panel of 45 neurologists, psychiatrists and gerontologists was invited to establish a formal consensus on the screening of pAD in China. The supportive evidence and grades of recommendations are based on a systematic literature review and focus group discussion. National meetings were held to allow participants to review, vote and provide their expert opinions to reach a consensus. A majority (two-thirds) decision was used for questions for which consensus could not be reached. Recommended screening methods are presented in this publication, including neuropsychological assessment, peripheral biomarkers and brain imaging. In addition, a general workflow for screening pAD in China is established, which will help clinicians identify individuals at high risk and determine therapeutic targets.

Prodromal Alzheimer's Disease: Global Cognition, Cue Efficiency, and Cerebrospinal Fluid Neurofilament Light Values Predict Short-Term Conversion to Dementia

Background

Predicting which patients with prodromal AD (pAD) will imminently convert to dementia may be paramount in a memory clinical setting, especially with potential disease-modifying therapies on the horizon.

Objective

To explore a practical tool for this prediction, combining cognitive tests and cerebrospinal fluid (CSF) biomarkers.

Methods

We designed a longitudinal prospective, observational, and multicenter study, enrolling patients with pAD. Inclusion criteria comprised memory complaints, Mini-Mental State Examination (MMSE) score of≥22, memory impairment as indicated by the Free and Cued Selective Reminding Test with Immediate Recall (FCSRT + IR) and/or TMA-93, Clinical Dementia Rating-Global Score (CDR-GS) of 0.5, and positive CSF Aβ42/Aβ40 ratio (<0.095, Euroimmun). The primary outcome was the conversion to dementia (CDR-GS≥1) within the first year of follow-up, referred to as "short-term conversion". A multiple regression logistic model was adopted to design the "Predict Short-Term Conversion" (PSTC) score.

Results

Between 2020 and 2022, 83 patients were recruited. The median age was 74, with 49.4% being women. Twenty-five (30.1%) patients were classified as short-term converters. The PSTC score incorporated baseline scores on MMSE ( ≤24 = 3, >24 = 0) and FCSRT + IR Total Recall ( ≤14 = 4, >14 = 0), and CSF neurofilament light chains (NfLs) concentrations (β=0.001299). The PSTC score demonstrated an area under the curve of 0.78 (95% CI: 0.67-0.90, p < 0.001), with a cutoff value of 5.14 presenting 76% sensitivity and 80% specificity.

Conclusions

The PSTC score, comprising two relatively brief cognitive test scores and NfLs CSF concentrations, could be useful for predicting short-term converters among patients diagnosed with pAD.

The "when" matters: Evidence from memory markers in the clinical continuum of Alzheimer's disease

OBJECTIVE

Cognitive assessment able to detect impairments in the early neuropathological stages of Alzheimer's disease (AD) is urgently needed. The visual short-term memory binding task (VSTMBT) and the Free and Cued Selective Reminding Test (FCSRT) have been recommended by the neurodegenerative disease working group as promising tests to aid in the early detection of AD. In this study, we investigated their complementary value across the clinical stages of the AD continuum.

METHOD

One hundred and seventeen older adults with subjective cognitive complaint (SCC), 79 with mild cognitive impairment (MCI), 31 patients with AD dementia (ADD), and 37 cognitively unimpaired (CU) subjects, underwent assessment with the VSTMBT and the picture version of the Spanish FCSRT.

RESULTS

After controlling for multiple comparisons, significant differences were found across groups. The VSTMBT was the only test that "marginally" differentiated between CU and SCC (d = 0.47, p = .052). Moreover, whereas the FCSRT showed a gradient (CU = SCC) > MCI > ADD, the VSTMBT gradient was CU > SCC > (MCI = ADD) suggesting that conjunctive binding deficits assessed by the latter may be sensitive to the very early stages of the disease.

CONCLUSIONS

Our results suggest that the VSTMBT and the FCSRT are sensitive to the clinical continuum of AD. Whereas the former detects changes in the early prodromal stages, the latter is more sensitive to the advanced prodromal stages of AD. These novel tests can aid in the early detection, monitor disease progression and response to treatment, and thus support drug development programs. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Dual-stage cognitive assessment: a two-stage screening for cognitive impairment in primary care

BACKGROUND

Aging population has led to an increased proportion of older adults and cognitively impaired. We designed a brief and flexible two-stage cognitive screening scale, the Dual-Stage Cognitive Assessment (DuCA), for cognitive screening in primary care settings.

METHOD

In total, 1,772 community-dwelling participants were recruited, including those with normal cognition (NC, n = 1,008), mild cognitive impairment (MCI, n = 633), and Alzheimer's disease (AD, n = 131), and administered a neuropsychological test battery and the DuCA. To improve performance, the DuCA combines visual and auditory memory tests for an enhanced memory function test.

RESULTS

The correlation coefficient between DuCA-part 1 and DuCA-total was 0.84 (P < 0.001). The correlation coefficients of DuCA-part 1 with Addenbrooke's Cognitive Examination III (ACE-III) and Montreal Cognitive Assessment Basic (MoCA-B) were 0.66 (P < 0.001) and 0.85 (P < 0.001), respectively. The correlation coefficients of DuCA-total with ACE-III and MoCA-B were 0.78 (P < 0.001) and 0.83 (P < 0.001), respectively. DuCA-Part 1 showed a similar discrimination ability for MCI from NC (area under curve [AUC] = 0.87, 95%CI 0.848-0.883) as ACE III (AUC = 0.86, 95%CI 0.838-0.874) and MoCA-B (AUC = 0.85, 95%CI 0.830-0.868). DuCA-total had a higher AUC (0.93, 95%CI: 0.917-0.942). At different education levels, the AUC was 0.83-0.84 for DuCA-part 1, and 0.89-0.94 for DuCA-total. DuCA-part 1 and DuCA-total's ability to discriminate AD from MCI was 0.84 and 0.93, respectively.

CONCLUSION

DuCA-Part 1 would aid rapid screening and supplemented with the second part for a complete assessment. DuCA is suited for large-scale cognitive screening in primary care, saving time and eliminating the need for extensively training assessors.

Shanghai Cognitive Screening: A Mobile Cognitive Assessment Tool Using Voice Recognition to Detect Mild Cognitive Impairment and Dementia in the Community

BACKGROUND

A rapid digital instrument is needed to facilitate community-based screening of mild cognitive impairment (MCI) and Alzheimer's disease (AD) in China.

OBJECTIVE

We developed a voice recognition-based cognitive assessment (Shanghai Cognitive Screening, SCS) on mobile devices and evaluated its diagnostic performance.

METHODS

Participants (N = 251) including healthy controls (N = 98), subjective cognitive decline (SCD, N = 42), MCI (N = 80), and mild AD (N = 31) were recruited from the memory clinic at Shanghai Sixth People's Hospital. The SCS is fully self-administered, takes about six minutes and measures the function of visual memory, language, and executive function. Participants were instructed to complete SCS tests, gold-standard neuropsychological tests and standardized structural 3T brain MRI.

RESULTS

The Cronbach's alpha was 0.910 of the overall scale, indicating high internal consistency. The SCS total score had an AUC of 0.921 to detect AD (sensitivity = 0.903, specificity = 0.945, positive predictive value = 0.700, negative predictive value = 0.986, likelihood ratio = 16.42, number needed for screening utility = 0.639), and an AUC of 0.838 to detect MCI (sensitivity = 0.793, specificity = 0.671, positive predictive value = 0.657, negative predictive value = 0.803, likelihood ratio = 2.41, number needed for screening utility = 0.944). The subtests demonstrated moderate to high correlations with the gold-standard tests from their respective cognitive domains. The SCS total score and its memory scores all correlated positively with relative volumes of the whole hippocampus and almost all subregions, after controlling for age, sex, and education.

CONCLUSION

The SCS has good diagnostic accuracy for detecting MCI and AD dementia and has the potential to facilitate large-scale screening in the general community.