Involvement of the reward network is associated with apathy in cerebral small vessel disease

Apathy After Stroke: Incidence, Symptom Trajectory, and Impact on Quality of Life and Disability

BACKGROUND AND OBJECTIVES

Apathy is one of the most common symptoms following stroke and is often associated with worse functional outcome and poor quality of life (QoL). The trajectory of apathy symptoms has been previously described, and different trajectories have been identified. We determined group and individual changes in apathy symptomatology from the acute phase until 1 year after stroke. We also examined the association of apathy and depression with disability and QoL 1 year after stroke.

METHODS

We measured apathy in a cohort of ischemic stroke survivors at 4 time points from 0 to 12 months after stroke. The Apathy Evaluation Scale (AES) and Dimensional Apathy Scale (DAS) were administered at each time point. Where possible we obtained apathy measured from carers. Depression was assessed with the Geriatric Depression Scale (GDS). Disability and QoL were assessed with the modified Rankin Scale (mRS) and 36-Item Short Form Survey (SF-36). We examined the cross-sectional and individual trajectory of apathy symptoms in each dimension and looked at associations of apathy and depression soon after stroke with mRS and SF-36 at 1 year.

RESULTS

Of 200 participants enrolled, 165 completed apathy measures at 12 months. Patient-rated apathy scores increased in both tests at the group level (AES: χ2(3) = 9.86, p = 0.019; DAS: χ2(3) = 8.49, p = 0.037) and individual level (AES: β = 0.13, p = 0.002; DAS β = 0.13, p = 0.005; DAS: executive β = 0.08, p < 0.001). By contrast, carer-rated apathy did not significantly increase (AES: χ2(3) = 0.75, p = 0.862; DAS: χ2(3) = 2.45, p = 0.484). Apathy scores were associated with worse mRS and SF-36, although most associations were no longer significant when controlling for depression. GDS was associated with worse mRS and SF-36 after controlling for covariates and apathy (mRS: β = 0.08, p = 0.006; SF-36 Mental Component Summary: β = -1.53, p < 0.001; SF-36 Physical Component Summary: β = -0.57, p = 0.016).

DISCUSSION

Self-reported apathy progressively increases after stroke, especially in the executive dimension. Apathy is associated with worse QoL and greater disability, although some of these associations might be mediated by depression.

Apathy is associated with striatal atrophy and cognitive impairment in cerebral small vessel disease

BACKGROUND

Apathy has been considered a common neuropsychiatric symptom and an important contributor to cognitive impairment in cerebral small vessel disease (SVD). However, the mechanism leading to apathy in SVD and the process whereby apathy promotes cognitive impairments remain largely unknown. We aimed to explore the relationship between apathy, cognition, and structural changes of deep grey matter (DGM) in SVD patients.

METHODS

Participants were screened for SVD, completed assessments of apathy cognition, underwent magnetic resonance imaging (MRI) scanning, and then stratified into apathy and non-apathy groups. We used region of interest (ROI)-based, voxel-based volume, and vertex-based shape analyses to compare DGM structures between study groups. Using linear regression analysis, we examined the association between apathy, structural changes, and cognition, followed by a mediation analysis of these factors.

RESULTS

A total of sixty-four SVD participants were included, with thirty in the apathy group and thirty-four in the non-apathy group. Intergroup comparison showed significantly lower volumes in bilateral caudate, right putamen, and pallidum and smaller vertex-based shapes in the right caudate and pallidum in participants with apathy compared to those without apathy. Apathy was associated with the striatal atrophy (i.e., lower volumes and smaller shape) and independently contributed to cognitive impairments in SVD. However, the above structural differences did not mediate the association between apathy and cognitive impairments.

CONCLUSION

These results highlight the important role of striatal atrophy in apathy in SVD and call for additional studies to explore the relationship between apathy, cognition, and DGM.

Strengths and Weaknesses of the Vascular Apathy Hypothesis: A Narrative Review

The vascular apathy hypothesis states that cerebral small vessel disease (CSVD) can cause apathy, even when no other symptoms of CSVD are present. In order to examine this hypothesis, the objectives of this narrative review are to evaluate the evidence for a pathophysiological mechanism linking CSVD to apathy and to examine whether CSVD can be a sole cause of apathy. The nature of the CSVD-apathy relationship was evaluated using the Bradford Hill criteria as a method for research on the distinction between association and causation. Pathological, neuroimaging, and behavioral studies show that CSVD can cause lesions in the reward network, which causes an apathy syndrome. Studies in healthy older individuals, stroke patients and cognitively impaired persons consistently show an association between CSVD markers and apathy, although studies in older persons suffering from depression are inconclusive. A biological gradient is confirmed, as well as a temporal relationship, although the evidence for the latter is still weak. The specificity of this causal relationship is low given there often are other contributing factors in CSVD patients with apathy, particularly depression and cognitive deterioration. Differentiating between vascular apathy and other apathy syndromes on the basis of clinical features is not yet possible, while in-depth knowledge about differences in the prognosis and efficacy of treatment options for apathy caused by CSVD and other apathy syndromes is lacking. Since we cannot differentiate between etiologically different apathy syndromes as yet, it is premature to use the term vascular apathy which would suggest a distinct clinical apathy syndrome.

Distinguishing apathy from depression: A review differentiating the behavioral, neuroanatomic, and treatment-related aspects of apathy from depression in neurocognitive disorders

OBJECTIVES

This narrative review describes the clinical features of apathy and depression in individuals with neurocognitive disorders (NCDs), with the goal of differentiating the two syndromes on the basis of clinical presentation, diagnostic criteria, neuropathological features, and contrasting responses to treatments.

METHODS

Literature was identified using PubMed, with search terms to capture medical conditions of interest; additional references were also included based on our collective experience and knowledge of the literature.

RESULTS

Evidence from current literature supports the distinction between the two disorders; apathy and depression occur with varying prevalence in individuals with NCDs, pose different risks of progression to dementia, and have distinct, if overlapping, neurobiological underpinnings. Although apathy is a distinct neuropsychiatric syndrome, distinguishing apathy from depression can be challenging, as both conditions may occur concurrently and share several overlapping features. Apathy is associated with unfavorable outcomes, especially those with neurodegenerative etiologies (e.g., Alzheimer's disease) and is associated with an increased burden for both patients and caregivers. Diagnosing apathy is important not only to serve as the basis for appropriate treatment, but also for the development of novel targeted interventions for this condition. Although there are currently no approved pharmacologic treatments for apathy, the research described in this review supports apathy as a distinct neuropsychiatric condition that warrants specific treatments aimed at alleviating patient disability.

CONCLUSIONS

Despite differences between these disorders, both apathy and depression pose significant challenges to patients, their families, and caregivers; better diagnostics are needed to develop more tailored treatment and support.

Contrast agent-free state-of-the-art magnetic resonance imaging on cerebral small vessel disease - Part 2: Diffusion tensor imaging and functional magnetic resonance imaging

Cerebral small vessel disease (cSVD) has been widely studied using conventional magnetic resonance imaging (MRI) methods, although the association between MRI findings and clinical features of cSVD is not always concordant. We assessed the additional contribution of contrast agent-free, state-of-the-art MRI techniques, particularly diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI), to understand brain damage and structural and functional connectivity impairment related to cSVD. We performed a review following the PICOS worksheet and Search Strategy, including 152 original papers in English, published from 2000 to 2022. For each MRI method, we extracted information about their contributions regarding the origins, pathology, markers, and clinical outcomes in cSVD. In general, DTI studies have shown that changes in mean, radial, and axial diffusivity measures are related to the presence of cSVD. In addition to the classical deficit in executive functions and processing speed, fMRI studies indicate connectivity dysfunctions in other domains, such as sensorimotor, memory, and attention. Neuroimaging metrics have been correlated with the diagnosis, prognosis, and rehabilitation of patients with cSVD. In short, the application of contrast agent-free, state-of-the-art MRI techniques has provided a complete picture of cSVD markers and tools to explore questions that have not yet been clarified about this clinical condition. Longitudinal studies are desirable to look for causal relationships between image biomarkers and clinical outcomes.

Sex Differences in Cerebral Small Vessel Disease: A Systematic Review and Meta-Analysis

Background: Cerebral small vessel disease (SVD) is a common cause of stroke, mild cognitive impairment, dementia and physical impairments. Differences in SVD incidence or severity between males and females are unknown. We assessed sex differences in SVD by assessing the male-to-female ratio (M:F) of recruited participants and incidence of SVD, risk factor presence, distribution, and severity of SVD features. Methods: We assessed four recent systematic reviews on SVD and performed a supplementary search of MEDLINE to identify studies reporting M:F ratio in covert, stroke, or cognitive SVD presentations (registered protocol: CRD42020193995). We meta-analyzed differences in sex ratios across time, countries, SVD severity and presentations, age and risk factors for SVD. Results: Amongst 123 relevant studies (n = 36,910 participants) including 53 community-based, 67 hospital-based and three mixed studies published between 1989 and 2020, more males were recruited in hospital-based than in community-based studies [M:F = 1.16 (0.70) vs. M:F = 0.79 (0.35), respectively; p < 0.001]. More males had moderate to severe SVD [M:F = 1.08 (0.81) vs. M:F = 0.82 (0.47) in healthy to mild SVD; p < 0.001], and stroke presentations where M:F was 1.67 (0.53). M:F did not differ for recent (2015-2020) vs. pre-2015 publications, by geographical region, or age. There were insufficient sex-stratified data to explore M:F and risk factors for SVD. Conclusions: Our results highlight differences in male-to-female ratios in SVD severity and amongst those presenting with stroke that have important clinical and translational implications. Future SVD research should report participant demographics, risk factors and outcomes separately for males and females. Systematic Review Registration: [PROSPERO], identifier [CRD42020193995].

Diagnostic criteria for apathy in neurocognitive disorders

INTRODUCTION

Apathy is common in neurocognitive disorders (NCD) but NCD-specific diagnostic criteria are needed.

METHODS

The International Society for CNS Clinical Trials Methodology Apathy Work Group convened an expert group and sought input from academia, health-care, industry, and regulatory bodies. A modified Delphi methodology was followed, and included an extensive literature review, two surveys, and two meetings at international conferences, culminating in a consensus meeting in 2019.

RESULTS

The final criteria reached consensus with more than 80% agreement on all parts and included: limited to people with NCD; symptoms persistent or frequently recurrent over at least 4 weeks, a change from the patient's usual behavior, and including one of the following: diminished initiative, diminished interest, or diminished emotional expression/responsiveness; causing significant functional impairment and not exclusively explained by other etiologies.

DISCUSSION

These criteria provide a framework for defining apathy as a unique clinical construct in NCD for diagnosis and further research.

Neuropsychiatric symptoms associated with cerebral small vessel disease: a systematic review and meta-analysis

BACKGROUND

Cerebral small vessel disease, a common cause of vascular dementia, is often considered clinically silent before dementia or stroke become apparent. However, some individuals have subtle symptoms associated with acute MRI lesions. We aimed to determine whether neuropsychiatric and cognitive symptoms vary according to small vessel disease burden.

METHODS

In this systematic review and meta-analysis, we searched MEDLINE, EMBASE, and PsycINFO for articles published in any language from database inception to Jan 24, 2020. We searched for studies assessing anxiety, apathy, delirium, emotional lability, fatigue, personality change, psychosis, dementia-related behavioural symptoms or cognitive symptoms (including subjective memory complaints), and radiological features of cerebral small vessel disease. We extracted reported odds ratios (OR), standardised mean differences (SMD), and correlations, stratified outcomes by disease severity or symptom presence or absence, and pooled data using random-effects meta-analyses, reporting adjusted findings when possible. We assessed the bias on included studies using the Risk of Bias for Non-randomized Studies tool. This study is registered with PROSPERO, CRD42018096673.

FINDINGS

Of 7119 papers identified, 81 studies including 79 cohorts in total were eligible for inclusion (n=21 730 participants, mean age 69·2 years). Of these 81 studies, 45 (8120 participants) reported effect estimates. We found associations between worse white matter hyperintensity (WMH) severity and apathy (OR 1·41, 95% CI 1·05-1·89) and the adjusted SMD in apathy score between WMH severities was 0·38 (95% CI 0·15-0·61). Worse WMH severity was also associated with delirium (adjusted OR 2·9, 95% CI 1·12-7·55) and fatigue (unadjusted OR 1·63, 95% CI 1·20-2·22). WMHs were not consistently associated with subjective memory complaints (OR 1·34, 95% CI 0·61-2·94) and unadjusted SMD for WMH severity between these groups was 0·08 (95% CI -0·31 to 0·47). Anxiety, dementia-related behaviours, emotional lability, and psychosis were too varied or sparse for meta-analysis; these factors were reviewed narratively. Overall heterogeneity varied from 0% to 79%. Only five studies had a low risk of bias across all domains.

INTERPRETATION

Apathy, fatigue, and delirium associated independently with worse WMH, whereas subjective cognitive complaints did not. The association of anxiety, dementia-related behaviours, emotional lability, and psychosis with cerebral small vessel disease require further investigation. These symptoms should be assessed longitudinally to improve early clinical detection of small vessel disease and enable prevention trials to happen early in the disease course, long before cognition declines.

FUNDING

Chief Scientist Office of the Scottish Government, UK Dementia Research Institute, Fondation Leducq, Stroke Association Garfield-Weston Foundation, Alzheimer's Society, and National Health Service Research Scotland.

Neuroanatomical Abnormalities in Older Depressed Adults With Apathy: A Systematic Review

OBJECTIVE

Apathy is a common phenomenon in late-life depression and is associated with poor outcomes. Apathy is often unrecognized in older depressed adults, and efficacious treatment options are lacking. This review provides a systematic review of the neuroanatomical abnormalities associated with apathy in late-life depression. In addition, the review summarizes the neuroimaging findings from studies of neurodegenerative and focal brain injury conditions that frequently present with apathy. The goal is to elucidate cerebral network abnormalities that give rise to apathy in older adults with mood disturbances and to inform future treatment targets.

METHOD

Systematic literature review.

RESULTS

The few studies that have directly examined the neuroanatomical abnormalities of apathy in late-life depression suggest disturbances in the anterior cingulate cortex, insula, orbital and dorsal prefrontal cortex, striatum, and limbic structures (ie, amygdala, thalamus, and hippocampus). Studies examining the neuroanatomical correlates of apathy in other aging populations are consistent with the pattern observed in late-life depression.

CONCLUSIONS

Apathy in late-life depression appears to be accompanied by neuroanatomical abnormalities in the salience and reward networks. These network findings are consistent with that observed in individuals presenting with apathy in other aging-related conditions. These findings may inform future treatments that target apathy.

Network neuroscience of apathy in cerebrovascular disease

Apathy is a reduction in motivated goal-directed behavior (GDB) that is prevalent in cerebrovascular disease, providing an important opportunity to study the mechanistic underpinnings of motivation in humans. Focal lesions, such as those seen in stroke, have been crucial in developing models of brain regions underlying motivated behavior, while studies of cerebral small vessel disease (SVD) have helped define the connections between brain regions supporting such behavior. However, current lesion-based models cannot fully explain the neurobiology of apathy in stroke and SVD. To address this, we propose a network-based model which conceptualizes apathy as the result of damage to GDB-related networks. A review of the current evidence suggests that cerebrovascular disease-related pathology can lead to network changes outside of initially damaged territories, which may propagate to regions that share structural or functional connections. The presentation and longitudinal trajectory of apathy in stroke and SVD may be the result of these network changes. Distinct subnetworks might support cognitive components of GDB, the disruption of which results in specific symptoms of apathy. This network-based model of apathy may open new approaches for investigating its underlying neurobiology, and presents novel opportunities for its diagnosis and treatment.

Empirical support for the vascular apathy hypothesis: A structured review

OBJECTIVES

A systematic review of the relationship between subclinical small vessel disease (SSVD) in the general population and apathy to examine the hypothesis that apathy has a vascular basis.

METHODS

We searched for studies on associations between apathy and SSVD, operationalized as white matter hyperintensities (WMH) or white matter diffusivity changes, lacunar infarcts, cerebral microbleeds, decreasing cortical thickness, and perivascular spaces, while also peripheral proxies for SSVD were considered, operationalized as ankle brachial pressure index (ABI), intima media thickness, arterial stiffness, cardio-femoral pulse wave velocity, hypertension, or cardiovascular disease. Only eligible retrospective and prospective observational studies conducted in the general population were included.

RESULTS

The 14 studies eligible for review examined the associations between apathy and hypertension (3), ABI (1), arterial stiffness (1), cardiovascular disease (2), WMH (3), white matter diffusivity (2), cerebral microbleeds (1), or cortical thickness (3). Arterial stiffness and white matter diffusivity were not related to apathy, while the associations with cortical thickness were contradictory. Cross-sectional studies in the general population did find evidence of apathy being associated with WMH, CM, cardiovascular disease, hypertension, and ABI, and cardiovascular disease was prospectively associated with apathy. The methodologies of the studies reviewed were too heterogeneous to perform meta-analyses.

CONCLUSIONS

Although more prospective evidence is needed and vascular depression needs to be controlled for, cardiovascular disease, hypertension, and ABI as proxies for SSVD, and WMH and cerebral microbleeds as direct measures of SSVD have been found to be associated with apathy in the general population, supporting the hypothesis of vascular apathy.

Review of diffusion MRI studies in chronic white matter diseases

Diffusion MRI studies characterizing the changes in white matter (WM) due to vascular cognitive impairment, which includes all forms of small vessel disease are reviewed. We reviewed the usefulness of diffusion methods in discriminating the affected WM regions and its relation to cognitive impairment. These studies were categorized based on the diffusion MRI techniques used. The most common method was the diffusion tensor imaging, whereas other methods included diffusion weighted imaging, diffusion kurtosis imaging, intravoxel incoherent motion, and studies based on diffusion tractography. The diffusion measures showed correlation with cognitive scores and disease progression, with mean diffusivity being the most robust parameter. Future studies should focus on incorporating multi-compartment and higher order diffusion models, which can handle the presence of multiple and crossing fibers inside a voxel.