Diagnosis and Management of Posterior Cortical Atrophy

Survival Differences Between Individuals With Typical and Atypical Phenotypes of Alzheimer Disease

BACKGROUND AND OBJECTIVES

Survival estimates for individuals with Alzheimer disease (AD) are informative to understand the disease trajectory, but precise estimates for atypical AD variants are scarce. Atypical AD variants are characterized by nonamnestic phenotypes, an early onset, and lower prevalence of APOEε4 carriership, which affect the AD trajectory. We aimed to provide survival estimates for posterior cortical atrophy (PCA), logopenic variant primary progressive aphasia (lvPPA), and behavioral AD (bvAD) and to evaluate the effect of these atypical AD diagnoses beyond known mortality determinants.

METHODS

From the Amsterdam Dementia Cohort, we retrospectively selected patients with biomarker-confirmed sporadic AD presenting at the memory clinic in the mild cognitive impairment or dementia stage. Patients were classified into atypical AD phenotypes (PCA, lvPPA, bvAD; multidisciplinary consensus and retrospective case finding) and a typical AD reference group (excluding unclassifiable atypical presentations or unconfirmed future AD dementia). Survival estimates from the first visit to death/censoring (Central Public Administration) were determined (Kaplan-Meier analysis) and compared (log-rank tests) across diagnostic groups. To assess associations of atypical AD with mortality, Cox proportional hazard models were constructed including age, sex, education, MMSE score, and APOEε4 carriership (model 1), followed by adding the atypical AD group (model 2) or atypical AD variants (model 3). A likelihood ratio test was performed to compare the fit of model 1 and model 2.

RESULTS

A total of 2,081 patients (aged 65 ± 8 years, 52% female) were classified as typical AD (n = 1,801) or atypical AD (n = 280; PCA [n = 112], lvPPA [n = 86], and bvAD [n = 82]). The estimated median survival time for atypical AD of 6.3 years (95% CI [5.8-6.9]) was shorter than for typical AD (7.2 [7.0-7.5], p = 0.02). Median survival durations across the atypical AD variants were consistently, albeit nonsignificantly, shorter (PCA: 6.3 [5.5-7.3], p = 0.055; lvPPA: 6.6 [5.7-7.7], p = 0.110; bvAD: 6.3 [5.0-9.1], p = 0.121, 48% deceased). Including atypical AD improved the model fit (model 2; χ2 = 8.88, p = 0.003) and was associated with 31% increased mortality risk compared with typical AD (hazard ratio [HR] = 1.31 [1.10-1.56], p = 0.002). In model 3, contributions of the variants were as follows: HRPCA = 1.35 (1.05-1.73), p = 0.019; HRlvPPA = 1.27 (0.94-1.69), p = 0.114; HRbvAD = 1.31 (0.94-1.83), p = 0.105.

DISCUSSION

Survival in atypical AD (PCA, lvPPA, bvAD) was shorter compared with typical AD. These atypical variants are associated with increased mortality beyond age, sex, education, APOEε4 carriership, and disease severity. Future studies are required to address generalizability of these findings and to identify factors that explain the observed survival differences.

'Dementia has got two faces': grief as an experience of holding on and letting go for people living with primary progressive aphasia and posterior cortical atrophy

BACKGROUND

research on grief in people with primary progressive aphasia (PPA) and posterior cortical atrophy (PCA), is limited, despite the unique challenges these individuals face due to lack of understanding of their condition, younger age at onset and atypical symptom profile. The current study explores the losses people living with PPA or PCA experience and what helps to navigate these losses.

METHODS

in-depth semi-structured research conversations were conducted with 14 participants (n = 8 PCA, 6 PPA) to explore experiences of grief and loss related to their dementia. Data was analysed using abductive thematic coding techniques.

RESULTS

the impact and navigation of loss is reflected across five interconnecting themes: what I have lost, am losing and will lose, shared and unique sense of loss, balance between what is lost and what remains, changes in relationships and what helps in navigating loss.

CONCLUSIONS

the dynamic interplay between what participants had lost and what they held on to carries significant implications for the design and delivery of support. These findings will be used alongside existing grief theory and interventional frameworks to develop a psychosocial intervention for people living with dementia.

Harmonizing Aβ deposition threshold for 18F-florbetaben PET imaging: Addressing discrepancies and calibration between PET/CT and PET/MRI

PURPOSE

Discrepancies between PET/CT and PET/MRI scanners can affect the determination of amyloid beta (Aβ) deposition thresholds in patients with cognitive impairment. This study aimed to identify these differences and propose a calibration method to standardize Aβ quantification across imaging modalities.

METHODS

A total of 133 patients with cognitive impairment underwent Aβ PET imaging and were divided into four groups: a head-to-head PET/CT and PET/MRI cohort (group A, n = 6), an independent PET/CT cohort (group B, n = 48), an independent PET/MRI cohort (group C, n = 79), and another independent PET/MRI cohort (group D, n = 10). Standardized uptake value ratios (SUVR) of global cortical target (CTXsuvr) and centiloid (CL) values were compared within group A and between groups B and C. A whole cerebellum (WC)-referenced SUVR method was used to calibrate CL values in group C, with verification in group D.

RESULTS

CTXsuvr values were significantly higher in PET/MRI than in PET/CT in both group A (P < 0.05) and group C versus group B (P < 0.001). Aβ-negative/positive cases showed mean ± variance of CTXsuvr as 1.023 ± 0.104/1.479 ± 0.203 in group B and 1.146 ± 0.100/1.743 ± 0.254 in group C, with cutoffs of 1.140 (CL = 20) and 1.401 (CL = 60), respectively. WC-referenced calibration adjusted PET/MRI cutoff to 1.132 (CL = 19) in group C, aligning it with PET/CT thresholds and validated in group D.

CONCLUSION

WC-referenced SUVR calibration effectively mitigates differences in Aβ thresholds between PET/CT and PET/MRI, enhancing Aβ quantification standardization in multi-modal imaging.

Towards realistic simulation of disease progression in the visual cortex with CNNs

Convolutional neural networks (CNNs) and mammalian visual systems share architectural and information processing similarities. We leverage these parallels to develop an in-silico CNN model simulating diseases affecting the visual system. This model aims to replicate neural complexities in an experimentally controlled environment. Therefore, we examine object recognition and internal representations of a CNN under neurodegeneration and neuroplasticity conditions simulated through synaptic weight decay and retraining. This approach can model neurodegeneration from events like tau accumulation, reflecting cognitive decline in diseases such as posterior cortical atrophy, a condition that can accompany Alzheimer's disease and primarily affects the visual system. After each degeneration iteration, we retrain unaffected synapses to simulate ongoing neuroplasticity. Our results show that with significant synaptic decay and limited retraining, the model's representational similarity decreases compared to a healthy model. Early CNN layers retain high similarity to the healthy model, while later layers are more prone to degradation. The results of this study reveal a progressive decline in object recognition proficiency, mirroring posterior cortical atrophy progression. In-silico modeling of neurodegenerative diseases can enhance our understanding of disease progression and aid in developing targeted rehabilitation and treatments.

Cognitive rehabilitation in posterior cortical atrophy

Posterior cortical atrophy is an uncommon type of dementia often caused by Alzheimer's disease and characterised by progressive loss of visuospatial and perceptual abilities. Although there is no curative treatment, patients may benefit from a range of symptom-based techniques and strategies to address visuospatial deficits and apraxia, and to reduce disability. Specific techniques based on visual and tactile cues, adapted and assistive equipment, environmental modifications and skill training may help people with posterior cortical atrophy continue to carry on activities that are important to them. We share vignettes from patients treated in our clinics to illustrate the practical delivery and potential impact of these therapies.

Atypical Presentations of Alzheimer Disease

OBJECTIVE

This article provides a comprehensive review of the distinct features of four atypical Alzheimer disease (AD) variants: dysexecutive AD, behavioral variant AD, posterior cortical atrophy, and the logopenic variant of primary progressive aphasia. It also elucidates their clinical presentations, underlying pathophysiologic pathways, diagnostic indicators, and management requirements.

LATEST DEVELOPMENTS

Recent research has revealed that these atypical AD forms vary not only in clinical manifestations but in their functional neuroanatomy spanning a common pathophysiologic spectrum. Imaging techniques, such as MRI, fludeoxyglucose positron emission tomography (FDG-PET), and tau PET, have identified distinct abnormalities in specific brain regions associated with each variant. This same variability is less tightly coupled to amyloid imaging. Emerging diagnostic and therapeutic strategies should be tailored to each variant's unique features.

ESSENTIAL POINTS

Atypical forms of AD often present with symptoms that are predominantly nonmemory related, distinguishing them from the more common memory-centric presentation of the disease. Two distinct clinical and pathologic entities, dysexecutive AD and behavioral variant AD, have replaced the outdated term frontal AD. Posterior cortical atrophy is another variant that mainly affects higher-order visual functions, which can lead to misdiagnoses because of its atypical symptom profile. Logopenic primary progressive aphasia is marked by difficulties in word retrieval, a challenge that may not be readily apparent if the person compensates by using circumlocution. Modern diagnostic techniques, such as MRI, PET, and biomarker analysis, have proven crucial for the accurate diagnosis and differentiation of these atypical AD variants. In treating these forms, it is critical to use tailored therapeutic interventions that combine pharmacotherapy with nonpharmacologic strategies to effectively manage the disease.

Preserved musical working memory and absolute pitch in posterior cortical atrophy

Working memory for nonverbal auditory information is essential for everyday functioning but its cognitive organisation is not well understood. Here we addressed this issue in a musician, YA, with absolute pitch (AP, the uncommon ability to categorise and label individual musical pitches without an external reference) who developed posterior cortical atrophy. We assessed YA's AP ability and her working memory for pitch and rhythmic patterns using procedures modelled on a standard test of auditory verbal working memory (digit span), referenced to age-matched, cognitively-normal AP and non-AP possessing musicians. YA had retained AP and performed comparably to healthy older AP and non-AP musicians on all musical working memory tasks, despite impaired auditory verbal working memory. These findings suggest that the cognitive mechanisms for auditory verbal working memory, nonverbal (pitch and rhythm) working memory and AP are at least partly dissociable, and both musical working memory and AP can be spared despite posterior parietal degeneration.

Effects of Route Complexity and Lighting on Route Following in Alzheimer's Disease and Posterior Cortical Atrophy

OBJECTIVE

Visual processing deficits arising in dementia are associated with particular functional disability. This study aimed to investigate the effects of the built environment on mobility and navigation in people with dementia-related visual loss.

METHODS

Participants with posterior cortical atrophy (PCA; "visual-variant Alzheimer's"; n = 11), typical Alzheimer's disease (tAD; N = 10), and controls (n = 13) repeatedly walked down routes within a simplified real-world setting. Participant groups were of comparable age and gender. Routes were of different complexity (straight, U-shaped, and S-shaped), overhead lighting levels (low and high) and with or without a dynamic LED (light-emitting diode) cue (trial n = 24). Ratios of walking times for each experimental condition (each complex route vs the straight route, high lighting vs low, and LED cue vs no cue) were compared between participant groups. Kinematic measures were produced from a total of 10,813 steps using wearable inertial measurement units (IMUs).

RESULTS

The walking time ratios relating to route complexity were higher in the PCA group than in controls: 30.3% (95% CI [13.5%, 49.5%] higher for U-shaped vs straight and 31.9% [21.1%, 55.3%] for S-shaped vs straight, averaged over other conditions). The analogous results relating to route complexity for the tAD group were intermediate between those for the PCA and control groups. There was no evidence that walking time ratios differed according to lighting level or the presence of the LED cue.

CONCLUSIONS

Findings contribute to evidence-based design for dementia-friendly environments, emphasizing consequences of environmental complexity for functional independence and mobility in people with dementia-related visual loss. Findings inform recommendations for environmental design to support the independence of individuals with dementia.

A Case of Posterior Cortical Atrophy in Alzheimer's Disease

This is a case of a 67-year-old male diagnosed with posterior cortical atrophy. Posterior cortical atrophy is an underdiagnosed phenomenon seen in neurodegenerative diseases, such as Alzheimer's disease. When this condition manifests in patients with Alzheimer's disease, it is known as a visual variant of Alzheimer's disease. This condition leads to visual disturbances that are due to processing errors in the brain, leaving cognitive functioning unchanged. Patients tend to undergo years of unnecessary ophthalmologic workup leading to unnecessary cost and frustration to the patient. The presentation and diagnostic workup of this disease are discussed in this case report.

"I Want to Do Something" - Exploring What Makes Activities Meaningful for Community-Dwelling People Living With Dementia: A Focused Ethnographic Study

Supporting ageing in place, quality of life, and activity engagement are public health priorities for people with dementia. The importance of maintaining opportunities for meaningful activities has been widely acknowledged for those with dementia in long-term care, but little is known about what makes activities meaningful for, and how they are experienced by, people with different types of dementia in their own homes. This study used focussed ethnographic methods to explore the motivations and meanings of everyday activity engagement within the homes of 10 people with memory-led Alzheimer's disease and 10 people with posterior cortical atrophy. While participants' interactions with their everyday environments were challenged by their diagnoses, they were all finding ways to continue meaning-making via various activities. The main findings are encapsulated in three themes: (1) The fun and the function of activities; (2) Reciprocities of care, and (3) The constitution and continuity of (a changing) self. Ongoing engagement with both fun and functional activities offered participants living with different dementias opportunities to connect with others, to offer care and support (as well as receive it), and to maintain a sense of self and identity. Implications are discussed regarding the development and delivery of tailored interventions and support to enable continued engagement in meaningful activities for people with different types of dementia living in the community.

The Graded Incomplete Letters Test (GILT): a rapid test to detect cortical visual loss, with UK Biobank implementation

Impairments of object recognition are core features of neurodegenerative syndromes, in particular posterior cortical atrophy (PCA; the 'visual-variant Alzheimer's disease'). These impairments arise from damage to higher-level cortical visual regions and are often missed or misattributed to common ophthalmological conditions. Consequently, diagnosis can be delayed for years with considerable implications for patients. We report a new test for the rapid measurement of cortical visual loss - the Graded Incomplete Letters Test (GILT). The GILT is an optimised psychophysical variation of a test used to diagnose cortical visual impairment, which measures thresholds for recognising letters under levels of increasing visual degradation (decreasing "completeness") in a similar fashion to ophthalmic tests. The GILT was administered to UK Biobank participants (total n=2,359) and participants with neurodegenerative conditions characterised by initial cortical visual (PCA, n=18) or memory loss (typical Alzheimer's disease, n=9). UK Biobank participants, including both typical adults and those with ophthalmological conditions, were able to recognise letters under low levels of completeness. In contrast, participants with PCA consistently made errors with only modest decreases in completeness. GILT sensitivity to PCA was 83.3% for participants reaching the 80% accuracy cut-off, increasing to 88.9% using alternative cut-offs (60% or 100% accuracy). Specificity values were consistently over 94% when compared to UK Biobank participants without or with documented visual conditions, regardless of accuracy cut-off. These first-release UK Biobank and clinical verification data suggest the GILT has utility in both rapidly detecting visual perceptual losses following posterior cortical damage and differentiating perceptual losses from common eye-related conditions.

The impact of empowerment theory-based health education on Alzheimer's disease informal caregivers: a randomized controlled trial

Background

There is a lack of evidence regarding the effectiveness of empowerment healthy education for caregivers of Alzheimer's patients.

Objective

To explore the effectiveness of the intervention of health education guided by empowerment theory on dementia knowledge, caregiving readiness, positive caregiving emotions, anxiety, and depression in informal Alzheimer's disease caregivers.

Design

A single-blinded, randomized controlled trial.

Setting

A teaching hospital in Tianjin, China.

Participants

Eighty caregivers of Alzheimer's disease patients.

Methods

Participants were recruited from the hospital and randomly assigned to either experimental or control group. The experimental group underwent a 12-weeks, one-to-one intervention of six session lasting 45-60 min each. The control group received conventional health education. Outcome measures included dementia knowledge, caregiver readiness (primary outcomes), positive caregiving emotions, anxiety, and depression (secondary outcomes).

Results

After 12 weeks, the intervention group exhibited significantly higher levels of dementia knowledge, caregiver readiness, and positive caregiving emotions compared with the control group. Furthermore, levels of hospitalization-related anxiety and depression were lower in the intervention group. All study results of this study showed statistically significant differences (p < 0.05).

Discussion

Empowerment theory-based health education appears to be an effective intervention for improving caregiver and readiness to care for caregivers of Alzheimer's disease individuals. The intervention may help reduce caregivers' anxiety and depression levels.

Rationale and design of the BeyeOMARKER study: prospective evaluation of blood- and eye-based biomarkers for early detection of Alzheimer's disease pathology in the eye clinic

BACKGROUND

Alzheimer's disease (AD) is a common, complex and multifactorial disease that may require screening across multiple routes of referral to enable early detection and subsequent future implementation of tailored interventions. Blood- and eye-based biomarkers show promise as low-cost, scalable and patient-friendly tools for early AD detection given their ability to provide information on AD pathophysiological changes and manifestations in the retina, respectively. Eye clinics provide an intriguing real-world proof-of-concept setting to evaluate the performance of these potential AD screening tools given the intricate connections between the eye and brain, presumed enrichment for AD pathology in the aging population with eye disorders, and the potential for an accelerated diagnostic pathway for under-recognized patient groups.

METHODS

The BeyeOMARKER study is a prospective, observational, longitudinal cohort study aiming to include individuals visiting an eye-clinic. Inclusion criteria entail being ≥ 50 years old and having no prior dementia diagnosis. Excluded eye-conditions include traumatic insults, superficial inflammation, and conditions in surrounding structures of the eye that are not engaged in vision. The BeyeOMARKER cohort (n = 700) will undergo blood collection to assess plasma p-tau217 levels and a brief cognitive screening at the eye clinic. All participants will subsequently be invited for annual longitudinal follow-up including remotely administered cognitive screening and questionnaires. The BeyeOMARKER + cohort (n = 150), consisting of 100 plasma p-tau217 positive participants and 50 matched negative controls selected from the BeyeOMARKER cohort, will additionally undergo Aβ-PET and tau-PET, MRI, retinal imaging including hyperspectral imaging (primary), widefield imaging, optical coherence tomography (OCT) and OCT-Angiography (secondary), and cognitive and cortical vision assessments.

RESULTS

We aim to implement the current protocol between April 2024 until March 2027. Primary outcomes include the performance of plasma p-tau217 and hyperspectral retinal imaging to detect AD pathology (using Aβ- and tau-PET visual read as reference standard) and to detect cognitive decline. Initial follow-up is ~ 2 years but may be extended with additional funding.

CONCLUSIONS

We envision that the BeyeOMARKER study will demonstrate the feasibility of early AD detection based on blood- and eye-based biomarkers in alternative screening settings, and will improve our understanding of the eye-brain connection.

TRIAL REGISTRATION

The BeyeOMARKER study (Eudamed CIV ID: CIV-NL-23-09-044086; registration date: 19th of March 2024) is approved by the ethical review board of the Amsterdam UMC.

'Communication is difficult': Speech, language and communication needs of people with young onset or rarer forms of non-language led dementia

BACKGROUND

People with behavioural variant frontotemporal dementia, Lewy body dementia, posterior cortical atrophy and young onset Alzheimer's disease may experience language and communication difficulties. However, the role of speech and language interventions for people with these non-language led dementias has received little attention.

AIMS

This study aimed to explore the experiences and perspectives of people living with these conditions, and their families, regarding their language and communication difficulties and how speech and language therapy could address these needs.

METHODS

This study employed a qualitative design to explore the experiences of people living with or caring for somebody with behavioural variant frontotemporal dementia, Lewy body dementia, posterior cortical atrophy or young onset Alzheimer's disease, and to understand their opinions about speech and language therapy. Participants were recruited from a support service connected to a dementia clinic to attend one of five focus group meetings. Videorecorded focus groups and interviews were transcribed, and reflexive thematic analysis was used to analyse data from people affected by each type of dementia.

RESULTS

A total of 25 participants were recruited to the study, with representation across the different forms of non-language led dementias. The four main themes identified were: (1) communication difficulties as a key difficulty, (2) loss and loneliness, (3) speech and language therapy, and (4) the role of the caregiver. Sixteen subthemes were also identified which highlighted individual issues across disease types.

DISCUSSION

Although all the forms of dementia studied here are not considered to be language-led, people with these conditions and/or their care partners identified speech, language and communication as common challenges. These communication difficulties were reported to have a negative impact on their social participation and mental health and participants felt speech and language interventions could help. There is a need for research exploring speech and language interventions developed for and with people with non-language led dementias and their care partners, to ensure they meet the needs of the people they are designed for.

WHAT THIS PAPER ADDS

What is already known on the subject People with primary progressive aphasia present with speech, language and communication difficulties, and several speech and language interventions have been developed to meet the needs of this population. However, people with non-language led dementias may also experience speech, language and communication difficulties, and little is known about interventions that may address these difficulties. What this paper adds to existing knowledge People living with or caring for somebody with behavioural variant frontotemporal dementia, Lewy body dementia, posterior cortical atrophy and young onset Alzheimer's disease report experiencing speech, language and communication difficulties that impact on the person with dementia's social participation and mood. Participants in this study also shared their opinions about how speech and language interventions could help, from the earliest stages of the disease. What are the potential or actual clinical implications of this work? Speech and language therapists need to address the individual speech, language and communication needs of people with dementias, even those that are not thought to be language-led. Current speech and language therapy service provision does not meet the needs of people with non-language led dementias and further research is required to develop interventions and services to meet these needs.

Rehabilitation Services for Young-Onset Dementia: Examples from High- and Low-Middle-Income Countries

The WHO Dementia Global Action Plan states that rehabilitation services for dementia are required to promote health, reduce disability, and maintain quality of life for those living with dementia. Current services, however, are scarce, particularly for people with young-onset dementia (YOD). This article, written by an international group of multidisciplinary dementia specialists, offers a three-part overview to promote the development of rehabilitation services for YOD. Firstly, we provide a synthesis of knowledge on current evidence-based rehabilitative therapies for early-onset Alzheimer's disease (EOAD), behavioural variant frontotemporal dementia (bvFTD), primary progressive aphasia (PPA), and posterior cortical atrophy (PCA). Secondly, we discuss the characteristics of rehabilitation services for YOD, providing examples across three continents for how these services can be embedded in existing settings and the different roles of the rehabilitation multidisciplinary team. Lastly, we conclude by highlighting the potential of telehealth in making rehabilitation services more accessible for people with YOD. Overall, with this paper, we aim to encourage clinical leads to begin introducing at least some rehabilitation into their services, leveraging existing resources and finding support in the collective expertise of the broader multidisciplinary dementia professional community.

Peer Support for Caregivers of People Living with Posterior Cortical Atrophy in Melbourne, Australia: A Feasibility Study

Posterior Cortical Atrophy (PCA) is a rare form of young-onset dementia that causes early visuospatial and visuoperceptual deficits. The symptom profile of Posterior Cortical Atrophy leads to very specific care needs for those affected, who often rely on informal caregivers (including friends and family). Rare dementia support groups can be useful for both patients and their caregivers to assist with knowledge sharing, psychoeducation, and the provision of psychosocial support. Despite this, few such support groups exist. The purpose of this study was to examine a PCA support group for caregivers of individuals living with PCA. We held a structured psychoeducation support group comprised of four sessions with the aim being to provide education, strategies for the management of the disease, and peer support. Caregivers' mental health and quality of life were assessed. The results of our study showed that support group participation was a positive experience and assisted with increasing the knowledge of caregivers and fostering social connections. We suggest that peer support groups may be beneficial for both people living with PCA and their caregivers. We recommend that future quantitative and qualitative research is conducted to further assess health-promotion benefits to people living with PCA and their caregivers, and to assess their development and implementation in different contexts.

Potential ocular indicators to distinguish posterior cortical atrophy and typical Alzheimer's disease: a cross-section study using optical coherence tomography angiography

BACKGROUND

Posterior cortical atrophy (PCA) is a form of dementia that frequently displays significant visual dysfunction and relatively preserved cognitive and executive functions, thus hindering early diagnosis and treatment. This study aimed to investigate possible fundus markers in PCA patients and compare them with those of typical Alzheimer's disease (AD) patients to seek potential diagnostic patterns.

METHODS

Age-matched PCA and AD patients and healthy controls (HC) completed optometry, intraocular pressure measurement, neuropsychologic assessments, optical coherence tomography (OCT), and optical coherence tomography angiography (OCTA) examination in one visit. Overall, six outcomes of thicknesses of various retinal layers and seven outcomes of the retinal microvascular network were calculated. After adjusting for age, sex, and years of education, the OCT and OCTA results were analyzed using analysis of covariance and generalized linear models. Correlation analyses were performed using Spearman correlation, and ROC curves were plotted.

RESULTS

Twelve PCA patients, nineteen AD patients, and thirty HC, aged 45-80 years were included. Fifty HC, thirty AD, and twenty PCA eyes were available for foveal avascular zone (FAZ) area analysis; forty-nine HC, thirty-four AD, and eighteen PCA eyes were available for OCT and OCTA assessments. PCA patients had thinner retinal nerve fiber layer and ganglion cell layer + inner plexiform layer than HC in the 0-3 mm circle and 1-3 mm ring. Few structural differences were observed between the AD group and the other two groups. The flow area of the superficial capillary plexus and the intermediate capillary plexus was smaller in the PCA group than in the HC group in the 0-1 mm circle, 0-3 mm circle. MMSE performed better than any combination of optical parameters in identifying AD and PCA from HC (AUC = 1), while the combination of MoCA, retinal thickness and vascular density of ICP in the 1-3 mm ring, with flow area of ICP in the 0-1 mm circle showed the strongest ability to distinguish PCA from AD (AUC = 0.944).

CONCLUSIONS

PCA patients exhibited similar impairment patterns to AD patients in the fundus structure and microvascular network. OCTA may aid in the non-invasive detection of AD and PCA, but still remains to be substantiated.

Evaluating the effect of kidney function on brain volumes and dementia risk in the UK Biobank

OBJECTIVE

To investigate the association between kidney function with the risk of dementia and brain volumes.

METHODS

A total of 452,996 UK Biobank participants with calculated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) were included. We utilized Cox proportional hazards regression models and restricted cubic spline analyses to examine the relationships between kidney function and the risk of all-cause dementia (ACD), Alzheimer's disease (AD), and vascular dementia (VD). Additionally, we explored the correlations between kidney function and brain magnetic resonance indicators among 40,380 participants.

RESULTS

During a median follow-up of 12 years, 5,258 incident ACD cases were identified. The deterioration of kidney function was associated with an increased risk of ACD. When compared to eGFR ≥ 90 ml/min/1.73 m², the highest risk increase was evident for eGFRcre < 30 ml/min/1.73 m² (adjusted HR = 2.372, 95% CI: 1.444-3.897, P < 0.001), with eGFRcys showing greater significance (adjusted HR = 3.045, 95% CI: 2.212-4.191, P < 0.001), especially in relation to AD. Compared to the ACR level in the range of 3-30 mg/mmol, the category of > 30 mg/mmol was associated with an increased risk of ACD (adjusted HR = 1.720, 95% CI: 1.350-2.190, P < 0.001). Moreover, the decline in kidney function was associated with the total brain volume atrophy and reduction in certain subcortical areas.

CONCLUSIONS

Our study indicates that diminished kidney function, as evidenced by a drop in eGFR and aggravated proteinuria, elevates dementia risk. Associated brain structural changes further underpin this connection from a neuro-pathophysiological perspective.

Neurophysiological Alterations of the Visual Pathway in Posterior Cortical Atrophy: Systematic Review and a Case Series

Background

The clinical features of posterior cortical atrophy (PCA), a rare condition often caused by Alzheimer's disease, have been recently defined, while little is known about its neurophysiological correlates.

Objective

To describe neurophysiological alterations of the visual pathway as assessed using visual field test (VF), visual evoked potentials (VEP), and electroretinogram (ERG) in PCA patients.

Methods

Studies reporting VF, VEPs, and ERG in PCA patients were selected according PRISMA method. Of the 323 articles that emerged from the literature, 17 included the outcomes of interest. To these data, we added those derived from a patient cohort enrolled at our clinic.

Results

The literature review included 140 patients, half of them (50%) presented with homonymous hemianopia or quadrantanopia. VEPs were available in 4 patients (2 normal findings, 1 decreased amplitude, and 1 increased latency) and ERG in 3 patients (substantially normal findings). Our case series included 6 patients, presenting with homonymous lateral hemianopia in 50% and contralateral cortical atrophy. VEPs showed normal amplitude in 66-83% according to the stimulation check, and increased latency in 67% in absence of myelin damage on MRI. Latency was increased in both eyes in 50% and only on one side in the other 50%. Such alterations were observed in patients with more severe and symmetric atrophy. ERG showed normal findings.

Conclusions

Neurophysiological investigations of the visual pathway in PCA are almost absent in literature. Alterations involve both amplitude and latency and can be also monocular. A multiple-point involvement of the optical pathway can be hypothesized.

Atypical forms of Alzheimer's disease: patients not to forget

PURPOSE OF REVIEW

The aim of this paper is to summarize the latest work on neuroimaging in atypical Alzheimer's disease (AD) patients and to emphasize innovative aspects in the clinic and research. The paper will mostly cover language (logopenic variant of primary progressive aphasia; lvPPA), visual (posterior cortical atrophy; PCA), behavioral (bvAD) and dysexecutive (dAD) variants of AD.

RECENT FINDINGS

MRI and PET can detect and differentiate typical and atypical AD variants, and novel imaging markers like brain iron deposition, white matter hyperintensities (WMH), cortical mean diffusivity, and brain total creatine can also contribute. Together, these approaches have helped to characterize variant-specific distinct imaging profiles. Even within each variant, various subtypes that capture the heterogeneity of cases have been revealed. Finally, in-vivo pathology markers have led to significant advances in the atypical AD neuroimaging field.

SUMMARY

Overall, the recent neuroimaging literature on atypical AD variants contribute to increase knowledge of these lesser-known AD variants and are key to generate atypical variant-specific clinical trial endpoints, which are required for inclusion of these patients in clinical trials assessing treatments. In return, studying these patients can inform the neurobiology of various cognitive functions, such as language, executive, memory, and visuospatial abilities.