A systematic review of neuroimaging in delirium: predictors, correlates and consequences

Small vessel disease contributions to acute delirium: a pilot feasibility MRI study

BACKGROUND AND AIMS

Delirium carries an eight-fold risk of future dementia. Small vessel disease (SVD), best seen on magnetic resonance imaging (MRI), increases delirium risk, yet delirium is understudied in MRI research. We aimed to determine MRI feasibility, tolerability, image usability and prevalence of SVD lesions in delirium.

METHODS

This case-control feasibility study performed MRI (3D T1/T2-weighted), fluid-attenuated inversion recovery, susceptibility-weighted and diffusion-weighted imaging (DWI) on 20 medical inpatients >65 years: 10 with delirium ≥3 weeks and 10 without delirium, matched for vascular risk, Clinical Frailty Scale (CFS) and cognition. We excluded acute stroke, agitation necessitating sedation, mobility assistance of >2 and MRI contraindications. We measured scan duration, tolerability, image usability, acute infarcts and SVD features. Six months later, we recorded CFS and cognitive diagnoses.

RESULTS

Mean age was 83.5 years (delirium 78.7 vs non-delirium 88.4); 13/20 were female; 17/20 had premorbid cognitive decline/impairment or dementia. Acquisition took mean 26.8 min. MRI was well tolerated in 16/20 (7/10 in delirium arm; 9/10 in non-delirium arm). Also, 4/20 had early scan termination, but 20/20 had clinically interpretable images. We detected DWI-hyperintense lesions in 3/10 (30%) with delirium (2/10 small subcortical and 1/10 cortical) and in 3/10 (30%) without delirium (2/10 small subcortical; 1/10 cortical). Mean white matter hyperintensity Fazekas score was 6 in delirium versus 4.5 without.

CONCLUSIONS

MRI is feasible, usable and tolerable in delirium, and we detected DWI-hyperintense lesions in one-third of all study participants, regardless of delirium status. This study indicates acute vascular contributions, including SVD, to both delirium- and non-delirium-related presentations, supporting the need for larger studies.

Neuroimaging Markers of Brain Reserve and Associations with Delirium in Patients with Intracerebral Hemorrhage

BACKGROUND

Delirium occurs frequently in patients with stroke, but the role of preexisting neural substrates in delirium pathogenesis remains unclear. We sought to explore associations between acute and chronic neural substrates of delirium in patients with intracerebral hemorrhage (ICH).

METHODS

Using data from a single-center ICH registry, we identified consecutive patients with acute nontraumatic ICH and available magnetic resonance imaging scans. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria were used to classify each patient as delirious or nondelirious during their hospitalization. Magnetic resonance imaging scans were processed and analyzed using semiautomated software, with volumetric measurement of acute ICH volume as well as white matter hyperintensity volume (WMHV) and gray and white matter volumes from the contralateral hemisphere. We tested associations between WMHV and incident delirium using multivariable regression models, and then determined the predictive accuracy of these neuroimaging models via area under the curve (AUC) analysis.

RESULTS

Of 139 patients in our cohort (mean [standard deviation] age 67.3 [17.3] years, 53% male), 58 (42%) patients experienced delirium. In our primary analyses, WMHV was significantly associated with delirium after adjusting for ICH features (odds ratio 1.56 per 10 cm3, 95% confidence interval 1.13-2.13), and this association was strengthened after further adjustment for segmented brain volume in patients with high-resolution scans (odds ratio 1.89 per 10 cm3, 95% confidence interval 1.24-2.86). Neuroimaging-based models predicted delirium with high accuracy (AUC 0.81), especially in patients with Glasgow Coma Scale score > 13 (AUC 0.85) and smaller ICH (AUC 0.91).

CONCLUSIONS

Chronic white matter disease is independently associated with delirium in patients with acute ICH, and neuroimaging biomarkers may have utility in predicting delirium occurrence.

Diffuse optical tomography for mapping cerebral hemodynamics and functional connectivity in delirium

INTRODUCTION

Delirium is associated with mortality and new onset dementia, yet the underlying pathophysiology remains poorly understood. Development of imaging biomarkers has been difficult given the challenging nature of imaging delirious patients. Diffuse optical tomography (DOT) offers a promising approach for investigating delirium given its portability and three-dimensional capabilities.

METHODS

Twenty-five delirious and matched non-delirious patients (n = 50) were examined using DOT, comparing cerebral oxygenation and functional connectivity in the prefrontal cortex during and after an episode of delirium.

RESULTS

Total hemoglobin values were significantly decreased in the delirium group, even after delirium resolution. Functional connectivity between the dorsolateral prefrontal cortex and dorsomedial prefrontal cortex was strengthened post-resolution compared to during an episode; however, this relationship was still significantly weaker compared to controls.

DISCUSSION

These findings highlight DOT's potential as an imaging biomarker to measure impaired cerebral oxygenation and functional dysconnectivity during and after delirium. Future studies should focus on the role of cerebral oxygenation in delirium pathogenesis and exploring the etiological link between delirium and dementias.

HIGHLIGHTS

We developed a portable diffuse optical tomography (DOT) system for bedside three-dimensional functional neuroimaging to study delirium in the hospital. We implemented a novel DOT task-focused seed-based correlation analysis. DOT revealed decreased cerebral oxygenation and functional connectivity strength in the delirium group, even after resolution of delirium.

Delirium in acute stroke is associated with increased cognitive and psychiatric symptoms over time: The Nor-COAST study

BACKGROUND

Delirium, an acute and fluctuating mental disturbance of attention, cognition, and consciousness, commonly occurs in acute stroke. Research on long-term outcomes of stroke patients experiencing delirium is limited, especially regarding cognitive and psychiatric symptoms.

METHODS

As part of the Nor-COAST study, 373 patients were screened for delirium using the Confusion Assessment Method (CAM) in the acute phase of stroke. Patients were included in the mixed-model linear regression analyses if they had available data from the follow-ups at three, 18 or 36 months, totaling 334 (44.6 % women, mean (SD) age: 72.1 (12.5) years, 17 (5.1 %) diagnosed with delirium). Global cognition was measured using the Montreal Cognitive Assessment (MoCA). Psychiatric symptoms were measured using the Hospital Anxiety and Depression Scale (HADS) and the Neuropsychiatric Inventory-Questionnaire (NPI-Q).

RESULTS

At three months, delirium was associated with a higher NPI-Q score (Mean (SD) 2.9 (3.6) vs 1.4 (2.2)). At 18 and 36 months, delirium was associated with a lower MoCA score (Mean (SD) 19.7 (6.6) vs 24.3 (5.0), and 20.6 (7.6) vs 24.6 (4.8)), higher HADS anxiety symptoms (5.0 (4.3) vs 3.3 (3.3), and 5.9 (4.1) vs 3.4 (3.6)), higher HADS depression symptoms (7.2 (4.7) vs 3.4 (3.3), and 6.6 (5.1) vs 3.7 (3.7)), and higher NPI-Q score (2.4 (4.4) vs 1.7 (2.3), 2.6 (4.5) vs 1.0 (1.9)). Delirium significantly predicted the psychiatric symptoms hallucinations and agitation.

CONCLUSIONS

Patients with delirium in the acute phase of stroke may be particularly vulnerable to developing cognitive and psychiatric symptoms in the chronic phase.

Infarct-related structural disconnection and delirium in surgical aortic valve replacement patients

OBJECTIVE

Although acute brain infarcts are common after surgical aortic valve replacement (SAVR), they are often unassociated with clinical stroke symptoms. The relationship between clinically "silent" infarcts and in-hospital delirium remains uncertain; obscured, in part, by how infarcts have been traditionally summarized as global metrics, independent of location or structural consequence. We sought to determine if infarct location and related structural connectivity changes were associated with postoperative delirium after SAVR.

METHODS

A secondary analysis of a randomized multicenter SAVR trial of embolic protection devices (NCT02389894) was conducted, excluding participants with clinical stroke or incomplete neuroimaging (N = 298; 39% female, 7% non-White, 74 ± 7 years). Delirium during in-hospital recovery was serially screened using the Confusion Assessment Method. Parcellation and tractography atlas-based neuroimaging methods were used to determine infarct locations and cortical connectivity effects. Mixed-effect, zero-inflated gaussian modeling analyses, accounting for brain region-specific infarct characteristics, were conducted to examine for differences within and between groups by delirium status and perioperative neuroprotection device strategy.

RESULTS

23.5% participants experienced postoperative delirium. Delirium was associated with significantly increased lesion volumes in the right cerebellum and temporal lobe white matter, while diffusion weighted imaging infarct-related structural disconnection (DWI-ISD) was observed in frontal and temporal lobe regions (p-FDR < 0.05). Fewer brain regions demonstrated DWI-ISD loss in the suction-based neuroprotection device group, relative to filtration-based device or standard aortic cannula.

INTERPRETATION

Structural disconnection from acute infarcts was greater in patients who experienced postoperative delirium, suggesting that the impact from covert perioperative infarcts may not be as clinically "silent" as commonly assumed.

Susceptibility to acute cognitive dysfunction in aged mice is underpinned by reduced white matter integrity and microgliosis

Age is a significant but heterogeneous risk factor for acute neuropsychiatric disturbances such as delirium. Neuroinflammation increases with aging but the determinants of underlying risk for acute dysfunction upon systemic inflammation are not clear. We hypothesised that, with advancing age, mice would become progressively more vulnerable to acute cognitive dysfunction and that neuroinflammation and neuronal integrity might predict heterogeneity in such vulnerability. Here we show region-dependent differential expression of microglial transcripts, but a ubiquitously observed primed signature: chronic Clec7a expression and exaggerated Il1b responses to systemic bacterial LPS. Cognitive frailty (vulnerability to acute disruption under acute stressors LPS and double stranded RNA; poly I:C) was increased in aged animals but showed heterogeneity and was significantly correlated with reduced myelin density, synaptic loss and severity of white matter microgliosis. The data indicate that white matter disruption and neuroinflammation may be key substrates of the progressive but heterogeneous risk for delirium in aged individuals.

Contribution of Different Brain Disorders and Multimorbidity to Delirium Superimposed Dementia (DSD)

Delirium, an acute neuropsychiatric disorder characterized by a disturbance of attention and awareness, is often superimposed on dementia with its progressive cognitive decline. Despite the high frequency and clinical relevance of this condition, often called delirium-superimposed dementia (DSD), little is known about possible triggers. In this study using the GePsy-B databank, we investigated the impact of the underlying brain disorder and multimorbidity (MM) on DSD. MM was measured by CIRS and the number of ICD-10 diagnoses. Dementia was diagnosed by CDR, and delirium by DSM IV TR criteria. A total of 218 patients were diagnosed with DSD and these were compared to 105 patients with only dementia, 46 with only delirium, and 197 patients suffering from other psychiatric diseases, mainly depression. No significant differences between groups were found concerning CIRS scores. Based on CT scans, DSD cases were grouped into those with cerebral atrophy only (probably pure neurodegenerative), with brain infarction, or with white matter hyperintensities (WMH), but no between-group differences regarding the MM indices could be found. Regression analysis only revealed age and dementia stage as influencing factors. Conclusion: Our results suggest that neither MM nor morphologic changes in the brain are predisposing factors for DSD.

Delirium in older hospitalized patients-A prospective analysis of the detailed course of delirium in geriatric inpatients

BACKGROUND

Delirium in older hospitalized patients (> 65) is a common clinical syndrome, which is frequently unrecognized.

AIMS

We aimed to describe the detailed clinical course of delirium and related cognitive functioning in geriatric patients in a mainly non-postoperative setting in association with demographic and clinical parameters and additionally to identify risk factors for delirium in this common setting.

METHODS

Inpatients of a geriatric ward were screened for delirium and in the case of presence of delirium included into the study. Patients received three assessments including Mini-Mental-Status-Examination (MMSE) and the Delirium Rating Scale Revised 98 (DRS-R-98). We conducted correlation and linear mixed-effects model analyses to detect associations.

RESULTS

Overall 31 patients (82 years (mean)) met the criteria for delirium and were included in the prospective observational study. Within one week of treatment, mean delirium symptom severity fell below the predefined cut-off. While overall cognitive functioning improved over time, short- and long-term memory deficits remained. Neuroradiological conspicuities were associated with cognitive deficits, but not with delirium severity.

DISCUSSION

The temporal stability of some delirium symptoms (short-/long-term memory, language) on the one hand and on the other hand decrease in others (hallucinations, orientation) shown in our study visualizes the heterogeneity of symptoms attributed to delirium and their different courses, which complicates the differentiation between delirium and a preexisting cognitive decline. The recovery from delirium seems to be independent of preclinical cognitive status.

CONCLUSION

Treatment of the acute medical condition is associated with a fast decrease in delirium severity. Given the high incidence and prevalence of delirium in hospitalized older patients and its detrimental impact on cognition, abilities and personal independence further research needs to be done.

Regional cerebral hypometabolism on 18F-FDG PET/CT scan in delirium is independent of acute illness and dementia

INTRODUCTION

Delirium is associated with new onset dementia and accelerated cognitive decline; however, its pathophysiology remains unknown. Cerebral glucose metabolism previously seen in delirium may have been attributable to acute illness and/or dementia. We aimed to statistically map cerebral glucose metabolism attributable to delirium.

METHODS

We assessed cerebral glucose metabolism using ¹⁸ F-fluorodeoxyglucose positron emission tomography (FDG-PET) in sick, older patients with and without delirium, all without clinical dementia (N = 20). Strict exclusion criteria were adopted to minimize the effect of established confounders on FDG-PET.

RESULTS

Patients with delirium demonstrated hypometabolism in the bilateral thalami and right superior frontal, right posterior cingulate, right infero-lateral anterior temporal, and left superior parietal cortices. Regional hypometabolism correlated with delirium severity and performance on neuropsychological testing.

DISCUSSION

In patients with acute illness but without clinical dementia, delirium is accompanied by regional cerebral hypometabolism. While some hypometabolic regions may represent preclinical Alzheimer's disease (AD), thalamic hypometabolism is atypical of AD and consistent with the clinical features that are unique to delirium.

Prediction of the development of delirium after transcatheter aortic valve implantation using preoperative brain perfusion SPECT

Objectives

Delirium is an important prognostic factor in postoperative patients undergoing cardiovascular surgery and intervention, including transcatheter aortic valve implantation (TAVI). However, delirium after transcatheter aortic valve implantation (DAT) is difficult to predict and its pathophysiology is still unclear. We aimed to investigate whether preoperative cerebral blood flow (CBF) is associated with DAT and, if so, whether CBF measurement is useful for predicting DAT.

Methods

We evaluated CBF in 50 consecutive patients before TAVI (84.7±4.5 yrs., 36 females) using ^99mTc ethyl cysteinate dimer single-photon emission computed tomography. Preoperative CBF of the DAT group (N = 12) was compared with that of the non-DAT group (N = 38) using whole brain voxel-wise analysis with SPM12 and region of interest-based analysis with the easy-Z score imaging system. Multivariable logistic regression analysis with the presence of DAT was used to create its prediction model.

Results

The whole brain analysis showed that preoperative CBF in the insula was lower in the DAT than in the non-DAT group (P<0.05, family-wise error correction). Decrease extent ratio in the insula of the DAT group (17.6±11.5%) was also greater relative to that of the non-DAT group (7.0±11.3%) in the region of interest-based analysis (P = 0.007). A model that included preoperative CBF in the insula and conventional indicators (frailty index, short physical performance battery and mini-mental state examination) showed the best predictive power for DAT (AUC 0.882).

Conclusions

These results suggest that preoperative CBF in the insula is associated with DAT and may be useful for its prediction.

The inter-relationship between delirium and dementia: the importance of delirium prevention

Delirium and dementia are two frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship. Delirium is an acute confusional state characterized by inattention, cognitive dysfunction and an altered level of consciousness, whereas dementia is an insidious, chronic and progressive loss of a previously acquired cognitive ability. People with dementia have a higher risk of developing delirium than the general population, and the occurrence of delirium is an independent risk factor for subsequent development of dementia. Furthermore, delirium in individuals with dementia can accelerate the trajectory of the underlying cognitive decline. Delirium prevention strategies can reduce the incidence of delirium and associated adverse outcomes, including falls and functional decline. Therefore, delirium might represent a modifiable risk factor for dementia, and interventions that prevent or minimize delirium might also reduce or prevent long-term cognitive impairment. Additionally, understanding the pathophysiology of delirium and the connection between delirium and dementia might ultimately lead to additional treatments for both conditions. In this Review, we explore mechanisms that might be common to both delirium and dementia by reviewing evidence on shared biomarkers, and we discuss the importance of delirium recognition and prevention in people with dementia.

In this Review, Fong and Inouye explore mechanisms that might be common to both delirium and dementia. They present delirium as a possible modifiable risk factor for dementia and discuss the importance of delirium prevention strategies in reducing this risk.

Delirium and dementia are frequent causes of cognitive impairment among older adults and have a distinct, complex and interconnected relationship.

Delirium prevention strategies have been shown to reduce not only the incidence of delirium but also the incidence of adverse outcomes associated with delirium such as falls and functional decline.

Adverse outcomes associated with delirium, such as the onset of dementia symptoms in individuals with preclinical dementia, and/or the acceleration of cognitive decline in individuals with dementia might also be delayed by the implementation of delirium prevention strategies.

Evidence regarding the association of systemic inflammatory and neuroinflammatory biomarkers with delirium is variable, possibly as a result of co-occurring dementia pathology or disruption of the blood–brain barrier.

Alzheimer disease pathology, even prior to the onset of symptoms, might have an effect on delirium risk, with potential mechanisms including neuroinflammation and gene–protein interactions with the APOE ε4 allele.

Novel strategies, including proteomics, multi-omics, neuroimaging, transcranial magnetic stimulation and EEG, are beginning to reveal how changes in cerebral blood flow, spectral power and connectivity can be associated with delirium; further work is needed to expand these findings to patients with delirium superimposed upon dementia.

Perivascular spaces visible on magnetic resonance imaging predict subsequent delirium in older patients

Background

It remains unknown whether perivascular spaces (PVS) are associated with delirium in older hospitalized patients. We aimed to determine the association between magnetic resonance imaging (MRI)-visible PVS and the risk of delirium in a cohort of older patients.

Methods

We consecutively recruited older patients (≥70 years) admitted to the Geriatric Department of West China Hospital between March 2016 and July 2017, and their imaging data within one year before admission were reviewed retrospectively. PVS was rated on axial T2-weighted images in the basal ganglia (BG) and centrum semiovale (CS) using the validated semiquantitative 4-point ordinal scale. Delirium was screened within 24 h of admission and three times daily thereafter, using the confusion assessment method. Binary logistic regression analyses were performed to investigate the associations between PVS and delirium.

Results

Among 114 included patients (mean age 84.3 years, 72.8% male), delirium occurred in 20 (17.5%). In patients with MRI examined within 6 months before admission, CS-PVS was found to be associated with delirium (odds ratio [OR] 3.88, 95% confidence interval [CI] 1.07-14.06, unadjusted; and OR 4.24, 95% CI 1.11-16.28, adjusted for age). The associations were enhanced and remained significant even after full adjustment of covariates (OR 7.16, 95% CI 1.16-44.32, adjusted for age, cognitive impairment, smoking, and Charlson Comorbidity Index). Similarly, the relationships between high CS-PVS and delirium were also strengthened after sequentially adjusting all variables of interest, with OR 4.17 (95% CI 1.04-16.73) in unadjusted model and OR 7.95 (95% CI 1.14-55.28) in fully-adjusted model. Adding CS-PVS to the established risk factors improved the risk reclassification for delirium (continuous net reclassification index 62.1%, P = 0.04; and integrated discrimination improvement 12.5%, P = 0.01).

Conclusions

CS-PVS on MRI acquired 6 months earlier predicts subsequent delirium in older patients and may have clinical utility in delirium risk stratification to enable proactive interventions.

Association between Baseline Cognitive Score and Postoperative Delirium in Parkinson’s Disease Patients following Deep Brain Stimulation Surgery

Background

Deep brain stimulation of the subthalamic nuclei (STN-DBS) is a standard treatment option for advanced Parkinson's disease (PD) patients. Delirium following DBS electrode implantation is common, by several studies, and cognitive impairment is a risk factor for developing postoperative delirium (POD). This prospective observational study was conducted to identify whether preoperative baseline cognitive status has an association with POD in PD patients undergoing DBS surgery.

Methods

Preoperatively, neuropsychiatric and neuropsychological assessments of the patients were performed including clinical dementia rating (CDR) score, instrumental activities of daily living (IADL) score, mini-mental state exam (MMSE) score, Montreal cognitive assessment (MoCA) score, Hamilton anxiety (HAMA) and Hamilton depression (HAMD) scores, and numerical cancellation test. POD was identified by the confusion assessment method (CAM) twice per day on postoperative day 1 until discharge.

Results

Twenty-seven (21.6%) of 125 patients developed POD. Among the variables screened, age, CDR score, MMSE score, and HAMA score were indicated to be independent influence factors of POD. The cutoff score, AUC, sensitivity, and specificity of age, CDR score, MMSE score, and HAMA score associated with POD was 58.5, 0.751, 92.6%, 52.0%; 0.5, 0.848, 77.8%, 91.8%; 27.5, 0.827, 88.9%, 62.2%; and 12.5, 0.706, 85.2%, 54.1%, respectively.

Conclusions

We observed age, CDR score, MMSE score, and HAMA score were independent influence factors of POD in PD patients who received DBS. It is necessary to assess the cognitive status of PD patients before surgery to identify high-risk patients.

Structural integrity of the anterior mid-cingulate cortex contributes to resilience to delirium in SuperAging

Despite its devastating clinical and societal impact, approaches to treat delirium in older adults remain elusive, making it important to identify factors that may confer resilience to this syndrome. Here, we investigated a cohort of 93 cognitively normal older patients undergoing elective surgery recruited as part of the Successful Aging after Elective Surgery study. Each participant was classified either as a SuperAger (n = 19) or typically aging older adult (n = 74) based on neuropsychological criteria, where the former was defined as those older adults whose memory function rivals that of young adults. We compared these subgroups to examine the role of preoperative memory function in the incidence and severity of postoperative delirium. We additionally investigated the association between indices of postoperative delirium symptoms and cortical thickness in functional networks implicated in SuperAging based on structural magnetic resonance imaging data that were collected preoperatively. We found that SuperAging confers the real-world benefit of resilience to delirium, as shown by lower (i.e. zero) incidence of postoperative delirium and decreased severity scores compared with typical older adults. Furthermore, greater baseline cortical thickness of the anterior mid-cingulate cortex-a key node of the brain's salience network that is also consistently implicated in SuperAging-predicted lower postoperative delirium severity scores in all patients. Taken together, these findings suggest that baseline memory function in older adults may be a useful predictor of postoperative delirium risk and severity and that superior memory function may contribute to resilience to delirium. In particular, the integrity of the anterior mid-cingulate cortex may be a potential biomarker of resilience to delirium, pointing to this region as a potential target for preventive or therapeutic interventions designed to mitigate the risk or consequences of developing this prevalent clinical syndrome.

Utility of white matter disease and atrophy on routinely acquired brain imaging for prediction of long-term delirium risk: population-based cohort study

Background

brain imaging done as part of standard care may have clinical utility beyond its immediate indication. Using delirium as an exemplar, we determined the predictive value of baseline brain imaging variables [white matter changes (WMC) and atrophy] for delirium risk on long-term follow-up after transient ischemic attack (TIA)/stroke in a population-based cohort study.

Methods

surviving TIA/stroke participants in the Oxford Vascular Study (OXVASC) were assessed prospectively for delirium during all hospitalisations over 6 months (2013–14). Using logistic regression, independent associations were determined between baseline OXVASC computed tomography or magnetic resonance brain imaging measures of WMC and cerebral atrophy (none/mild versus moderate/severe) and delirium adjusted for age, sex, baseline stroke severity, depression, illness severity and pre-admission cognition.

Results

among 1,565 TIA/stroke survivors with 194 hospital admissions (158 patients, mean/standard deviation age at admission = 79.2/11.5 years), delirium occurred in 59 (37%). WMC and atrophy on baseline imaging were associated with delirium [odds ratio (OR) = 3.41, 1.21–5.85, P = 0.001 and OR = 2.50, 1.23–5.08, P = 0.01 (unadjusted) and OR = 2.67, 1.21–5.85, P = 0.02 and OR = 2.18, 1.00–4.73, P = 0.05 (adjusted age and sex)]. Associations were strengthened when analyses were restricted to patients hospitalised within 5 years of baseline brain imaging [OR = 6.04, 2.39–15.24, P < 0.0001 and OR = 4.64, 1.46–14.82, P = 0.009 (unadjusted)] but only WMC remained significant after adjustment for all covariates including pre-admission cognition (OR = 4.83, 1.29–18.13, P = 0.02 for Mini-Mental State Examination and OR = 5.15, 1.26–21.09, P = 0.02 for Montreal Cognitive Assessment).

Conclusions

WMC and atrophy on brain imaging done up to 5 years earlier predicted delirium and may have clinical utility in risk stratification. Associations with WMC but not atrophy were independent of pre-admission cognitive impairment.

Chronic cerebral infarctions and white matter lesions link to long-term survival after a first ischemic event: A cohort study

BACKGROUND AND PURPOSE

To investigate the association of different phenotypes, count, and locations of chronic covert brain infarctions (CBI) with long-term mortality in patients with first-ever manifest acute ischemic stroke (AIS) or transient ischemic attack (TIA). Additionally, to analyze their potential interaction with white matter hyperintensities (WMH) and predictive value in addition to established mortality scores.

METHODS

Single-center cohort study including consecutive patients with first-ever AIS or TIA with available MRI imaging from January 2015 to December 2017. Blinded raters adjudicated CBI phenotypes and WMH (age-related white matter changes score) according to established definitions. We compared Cox regression models including prespecified established predictors of mortality using Harrell's C and likelihood ratio tests.

RESULTS

A total of 2236 patients (median [interquartile range] age: 71 [59-80] years, 43% female, National Institutes of Health Stroke Scale: 2 [1-6], median follow-up: 1436 days, 21% death during follow-up) were included. Increasing WMH (per point adjusted Hazard Ratio [aHR] = 1.29 [1.14-1.45]), but not CBI (aHR = 1.21 [0.99-1.49]), were independently associated with mortality. Neither CBI phenotype, count, nor location was associated with mortality and there was no multiplicative interaction between CBI and WMH (p &gt; .1). As compared to patients without CBI or WMH, patients with moderate or severe WMH and additional CBI had the highest hazards of death (aHR = 1.62 [1.23-2.13]). The Cox regression model including CBI and WMH had a small but significant increment in Harrell's C when compared to the model including 14 clinical variables (0.831 vs. 0.827, p &lt; .001).

DISCUSSION

WMH represent a strong surrogate biomarker of long-term mortality in first-ever manifest AIS or TIA patients. CBI phenotypes, count, and location seem less relevant. Incorporation of CBI and WMH slightly improves predictive capacity of established risk scores.

Cognitive Predictors of Delirium on Long-Term Follow-Up after TIA and Stroke: Population-Based Cohort Study

INTRODUCTION

TIA and stroke cause cognitive impairment with a typical "vascular" pattern, including prominent frontal/executive deficits. Cognitive impairment is associated with increased delirium risk and the few available data suggest that executive dysfunction is important. We therefore determined the predictive value of both severity and pattern of cognitive deficits for delirium on long-term follow-up after TIA/stroke.

METHODS

Surviving TIA/stroke participants on October 1, 2013, in the Oxford Vascular Study (OXVASC) were assessed prospectively for delirium during all hospitalizations over the subsequent 6 months. Associations between OXVASC pre-admission mini-mental state examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores, and delirium during hospitalizations on follow-up were determined using logistic regression adjusted for covariates, including demographic factors, history of depression, baseline stroke severity, and admission illness severity.

RESULTS

Among 1,565 TIA/stroke survivors, 158 patients (mean/SD age = 79.2/11.5 years) had ≥1 admission and 59 (37%) had ≥1 delirium episode. Mean/SD time between baseline TIA/stroke and admission was 4.7/3.6 years and between most recent OXVASC cognitive testing and admission was 1.7/1.8 years. MMSE and MoCA scores were associated with delirium: odds ratio (OR) = 1.16 (95% CI 1.07-1.27, p < 0.0001 per point decrease in MMSE) and OR = 1.20 (1.11-1.30, p < 0.0001 MoCA) and associations were robust to adjustment for all covariates, including stroke severity: OR = 1.11 (1.01-1.22, p = 0.03, MMSE) and OR = 1.15 (1.05-1.25, p = 0.003, MoCA). All 10 subtests on the MoCA and 4/11 on the MMSE were significantly associated with delirium with highest predictive value for frontal/executive and recall domains.

CONCLUSIONS

Cognitive impairment of increasing severity after TIA/stroke predisposed to delirium particularly deficits in frontal/executive domains and recall. Long-term risk of delirium should be considered as part of the overall cerebrovascular disease burden.

C-reactive protein and white matter microstructural changes in COVID-19 patients with encephalopathy

Encephalopathy is a neurological complication of COVID-19. The objective of this exploratory study is to investigate the link between systemic inflammation and brain microstructural changes (measured by diffusion-weighted imaging) in patients with COVID-19 encephalopathy. 20 patients with COVID-19 encephalopathy (age: 67.3 [Formula: see text] 10.0 years; 90% men) hospitalized in the Geneva University Hospitals for a SARS-CoV-2 infection between March and May 2020 were included in this retrospective cohort study. COVID-19 encephalopathy was diagnosed following a comprehensive neurobiological evaluation, excluding common causes of delirium, such as hypoxemic or metabolic encephalopathy. We investigated the correlation between systemic inflammation (measured by systemic C-reactive protein (CRP)) and brain microstructural changes in radiologically normal white matter (measured by apparent diffusion coefficient (ADC)) in nine spatially widespread regions of the white matter previously associated with delirium. Systemic inflammation (CRP = 60.8 ± 50.0 mg/L) was positively correlated with ADC values in the anterior corona radiata (p = 0.0089), genu of the corpus callosum (p = 0.0064) and external capsule (p = 0.0086) after adjusting for patients' age. No statistically significant association between CRP and ADC was found in the other six white matter regions. Our findings indicate high risk of white matter abnormalities in COVID-19 encephalopathy patients with high peripheral inflammatory markers, suggesting aggressive imaging monitoring may be warranted in these patients. Future studies should clarify a possible specificity of the spatial patterns of CRP-white matter microstructure association in COVID-19 encephalopathy patients and disentangle the role of individual cytokines on brain inflammatory mechanisms.

Intranasal insulin for treatment of delirium in older hospitalised patients: study protocol for a randomised controlled trial

INTRODUCTION

Delirium is one of the most common conditions diagnosed in hospitalised older people and is associated with numerous adverse outcomes, yet there are no proven pharmacological treatments. Recent research has identified cerebral glucose hypometabolism as a pathophysiological mechanism offering a therapeutic target in delirium. Insulin, delivered via the intranasal route, acts directly on the central nervous system and has been shown to enhance cerebral metabolism and improve cognition in patients with mild cognitive impairment and dementia. This trial will determine whether intranasal insulin can reduce the duration of delirium in older hospitalised patients.

METHODS AND ANALYSIS

This is a prospective randomised, placebo-controlled, double-blind study with 6 months follow-up. One hundred patients aged 65 years or older presenting to hospital with delirium admitted under geriatric medicine will be recruited. Participants will be randomised to intranasal insulin detemir or placebo administered twice daily until delirium resolves, defined as Confusion Assessment Method (CAM) negative for 2 days, or discharge from hospital. The primary outcome measure will be duration of delirium using the CAM. Secondary outcome measures will include length of hospital stay, severity of delirium, adherence to treatment, hospital complications, new admission to nursing home, mortality, use of antipsychotic medications during hospital stay and cognitive and physical function at 6 months postdischarge.

ETHICS AND DISSEMINATION

This trial has been approved by the South Eastern Sydney Human Research and Ethics Committee. Dissemination plans include submission to a peer-reviewed journal for publication and presentation at scientific conferences.

TRIAL REGISTRATION NUMBER

ACTRN12618000318280.

Delirium and abnormal autonomic nervous system response to head-up tilt testing

BACKGROUND

Delirium is a common condition with poorly understood pathophysiology. Various theories have been proposed including that delirious patients have reduced cerebral blood flow. We hypothesised that patients with delirium could have abnormal autonomic nervous system function, as assessed by tilt table testing, which would explain the alteration in blood flow.

METHODS

A prospective cohort study of medical inpatients aged 65 years and older was undertaken. Delirium was assessed using DRS-R98 and DSM-IV criteria. Beat-to-beat blood pressure (BP) was recorded during tilt testing. Differences in BP changes between the two groups (those with delirium and those without) were explored. The association between severity of delirium and magnitude of BP changes was also examined.

RESULTS

64 participants were recruited during hospitalisation. 29 completed follow-up Head-Up Tilt testing. The mean age of participants was 80.8 years (SD 6.2 years). The control group (n = 12) had a median decrease in systolic BP of 17.5 mmHg (IQR 20.75). The delirium group (n = 17) had a median decrease in systolic BP of 1 mmHg (IQR 38.5), p = 0.04. As delirium severity scores increased, systolic BP change during tilting also increased (r_s = 0.42, p = 0.03).

CONCLUSION

Participants in the delirium group showed different BP responses to tilt test which may represent abnormal sympathetic response. This would be consistent with other features of delirium such as treatment response to centrally acting alpha-2 blockers. Equity of access to research for older, frail and delirious cohorts is essential but feasibility and acceptability needs to be optimised and factored into study design.

Current Challenges in the Recognition and Management of Delirium Superimposed on Dementia

Delirium occurring in a patient with preexisting dementia is referred to as delirium superimposed on dementia (DSD). DSD commonly occurs in older hospitalized patients and is associated with worse outcomes, including higher rates of mortality and institutionalization, compared to inpatients with delirium or dementia alone. This narrative review summarizes the screening, diagnosis, management, and pathophysiology of DSD and concludes by highlighting opportunities for future research. Studies were identified via Medline and PsycINFO keyword search, and handsearching reference lists. Conceptually, DSD could be considered an "acute exacerbation" of dementia precipitated by a noxious insult akin to an acute exacerbation of heart failure or acute on chronic renal failure. However, unlike other organ systems, there are no established biomarkers for delirium, so DSD is diagnosed and monitored clinically. Because cognitive dysfunction is common to both delirium and dementia, the diagnosis of DSD can be challenging. Inattention, altered levels of arousal, and motor dysfunction may help distinguish DSD from dementia alone. An informant history suggestive of an acute change in cognition or alertness should be investigated and managed as delirium until proven otherwise. The key management principles include prevention, identifying and treating the underlying precipitant(s), implementing multicomponent interventions to create an ideal environment for brain recovery, preventing complications, managing distress, and monitoring for resolution. Informing and involving family members or caregivers throughout the patient journey are essential because there is significant prognostic uncertainty, including the risk of persistent cognitive and functional decline following DSD and relapse. Furthermore, informal carers can provide significant assistance in management. Emerging evidence demonstrates that increased exposure to delirium is associated with neuronal injury and worse cognitive outcomes although the mechanisms through which this occurs remain unclear. Given the clinical overlap between delirium and dementia, studying shared pathophysiological pathways may uncover diagnostic tests and is an essential step in therapeutic innovation.

Neurocognitive disorders in the elderly: altered functional resting-state hyperconnectivities in postoperative delirium patients

Postoperative delirium (POD) represents a confusional state during days/weeks after surgery and is particularly frequent in elderly patients. Hardly any fMRI studies were conducted to understand the underlying pathophysiology of POD patients. This prospective observational cohort study aims to examine changes of specific resting-state functional connectivity networks across different time points (pre- and 3-5 months postoperatively) in delirious patients compared to no-POD patients. Two-hundred eighty-three elderly surgical patients underwent preoperative resting-state fMRI (46 POD). One-hundred seventy-eight patients completed postoperative scans (19 POD). For functional connectivity analyses, three functional connectivity networks with seeds located in the orbitofrontal cortex (OFC), nucleus accumbens (NAcc), and hippocampus were investigated. The relationship of POD and connectivity changes between both time points (course connectivity) were examined (ANOVA). Preoperatively, delirious patients displayed hyperconnectivities across the examined functional connectivity networks. In POD patients, connectivities within NAcc and OFC networks demonstrated a decrease in course connectivity [max. F = 9.03, p = 0.003; F = 4.47, p = 0.036, resp.]. The preoperative hyperconnectivity in the three networks in the patients at risk for developing POD could possibly indicate existing compensation mechanisms for subtle brain dysfunction. The observed pathophysiology of network function in POD patients at least partially involves dopaminergic pathways.

Delirium in acute stroke: A prospective, cross-sectional, cohort study

BACKGROUND AND PURPOSE

Delirium is a neuropsychiatric disorder of attention and awareness that develops over a short time and fluctuates in severity. Although delirium has been extensively studied in intensive care units, the incidence of delirium in stroke units and its predictors in stroke patients need further investigation. The endpoints of our study were incidence of delirium in acute stroke and the risk factors that predispose to this condition.

METHODS

Patients were consecutively enrolled in a stroke unit from April to October 2020. Inclusion criteria were: age ≥18 years, acute stroke and National Institute of Health Stroke Scale (NIHSS) score ≥1 at the time of clinical assessment of delirium. Exclusion criteria were: transient ischemic attack; absence of neuroimaging evidence of brain lesion; cerebral venous thrombosis; subarachnoid hemorrhage; and clinical conditions requiring intensive care unit treatment. All patients were evaluated by means of Richmond Agitation-Sedation Scale (RASS) and Confusion Assessment Method-Intensive Care Unit (CAM-ICU) scores at baseline, evaluations which were repeated within 72 h or when patients developed symptoms suggesting delirium.

RESULTS

The overall incidence of delirium was 36/120 (30%). Delirium was associated with aphasia (odds ratio [OR] 9.77; confidence interval [CI] 1.2-79.6), chronic obstructive pulmonary disease (COPD; OR 16.67; CI 1.1-263.0), deep Fazekas score (OR 5.05; CI 1.7-14.8), and physical restraint (OR 45.02; CI 1.4-1411.5). Diabetes was associated with a lower incidence of delirium (OR 0.04; CI 0.026-0.7).

CONCLUSIONS

Nearly one-third of patients (30%) had delirium in the acute phase of stroke. This finding supports the notion that delirium is a common complication of stroke. Delirium was associated with speech disorder, leukoencephalopathy, COPD and early use of physical restraint.

Clinical utility of brain computed tomography in prediction of post-stroke delirium

Delirium is a common and serious complication of stroke. Early prediction of delirium is important for preventive strategies and close monitoring of high-risk patients. Pre-existing degenerative and vascular changes in the brain could predispose to delirium. We aimed to determine if computed tomography (CT)-based indices could provide additional information about a risk of stroke-associated delirium beyond easiest-to-access clinical predictors. Using semi-quantitative scales (global cortical atrophy, age-related white matter changes, and Scheltens scale), we assessed global and regional brain atrophy and white matter changes in 88 stroke patients with delirium and 142 patients without delirium matched for age and stroke severity. Patients with delirium had greater global and local brain atrophy (the right temporal region, the left parieto-occipital region, the right frontal and occipital horn, and the right and left temporal horn) than patients without delirium. Scores of white matter changes did not differ between groups with exception of greater white matter damage in the right parieto-occipital area in patients with delirium. The discriminatory properties of studied radiological indices were modest (areas under receiver operator curves: 0.58-0.64). CT-based indices of brain atrophy and white matter changes do not provide additional information about a risk of post-stroke delirium beyond the most important clinical predictors.

Delirium in the acute hospital setting: the role of psychiatry

In this overview we discuss the role of psychiatry in managing delirium in acute hospital admissions. We briefly discuss the role psychiatry can offer in four main domains: (a) assessment; (b) management; (c) recovery; and (d) paradigm, education and research. In the assessment section we discuss accurately detecting delirium in the context of comorbid mixed neuropsychiatric syndromes, including depression and dementia, and the clinical importance of delirium subtyping. The management section briefly outlines pharmacological and non-pharmacological approaches to delirium and their evidence-based rationale. The recovery section focuses on the effect delirium can have on cognitive decline, mental health and long-term health, including functional outcome and need for institutional care after hospital discharge. Finally, we outline the role of psychiatry in delirium research and education. We hope that this article will encourage clinicians to reflect on their current practice and consider holistic and evidence-based care for this vulnerable population in the acute hospital setting.

Delirium

Delirium, a syndrome characterized by an acute change in attention, awareness and cognition, is caused by a medical condition that cannot be better explained by a pre-existing neurocognitive disorder. Multiple predisposing factors (for example, pre-existing cognitive impairment) and precipitating factors (for example, urinary tract infection) for delirium have been described, with most patients having both types. Because multiple factors are implicated in the aetiology of delirium, there are likely several neurobiological processes that contribute to delirium pathogenesis, including neuroinflammation, brain vascular dysfunction, altered brain metabolism, neurotransmitter imbalance and impaired neuronal network connectivity. The Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) is the most commonly used diagnostic system upon which a reference standard diagnosis is made, although many other delirium screening tools have been developed given the impracticality of using the DSM-5 in many settings. Pharmacological treatments for delirium (such as antipsychotic drugs) are not effective, reflecting substantial gaps in our understanding of its pathophysiology. Currently, the best management strategies are multidomain interventions that focus on treating precipitating conditions, medication review, managing distress, mitigating complications and maintaining engagement to environmental issues. The effective implementation of delirium detection, treatment and prevention strategies remains a major challenge for health-care organizations globally.

A Systematic Review of Delirium Biomarkers and Their Alignment with the NIA-AA Research Framework

OBJECTIVES

To identify whether delirium biomarkers aligned with the National Institute on Aging-Alzheimer's Association (NIA-AA) research framework, a conceptual model that describes the use of diagnostic biomarkers for Alzheimer's disease and other related dementias (ADRD).

DESIGN

Systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

SETTING

Acute care and outpatient settings.

PARTICIPANTS

Adults diagnosed with delirium.

METHODS AND MEASUREMENTS

MEDLINE, PsycInfo, Embase, and the Cochrane Library were searched for English-language studies published from January 2010 to February 2020. Studies included adults older than 18 years, identified delirium with a standardized assessment tool, and measured an ADRD biomarker. Independent reviewers determined whether an association between delirium and ADRD biomarker was found, the quality of biomarker data based on the REMARK (REporting recommendations for tumor MARKer prognostic studies) checklist, and the study bias based on the Newcastle-Ottawa Scale.

RESULTS

A total of 61,256 citations were identified; 113 studies were included. Most studies did not examine amyloid, tau, or neurodegeneration biomarkers. Delirium may be associated with neurodegeneration biomarkers, but few to no studies found an association with amyloid and tau biomarkers. Delirium was not consistently associated with inflammatory biomarkers. The quality of biomarker data was moderate, and the risk of bias was moderate to high. Studies often did not collect prehospital and posthospital cognitive data.

CONCLUSION

Most delirium diagnostic biomarker studies did not measure amyloid, tau, and/or neurodegenerative biomarkers, making characterization of the relationship between delirium and ADRD difficult. Future delirium biomarker diagnostic studies could improve the understanding of pathophysiologic links between delirium with other conditions affecting cognition.

Clinical and Neuroimaging Correlates of Post-Transplant Delirium

Delirium is common among adults undergoing hematopoietic stem cell transplantation (HCT), although the clinical and neuroimaging correlates of post-HCT delirium have not been adequately delineated. We therefore examined the frequency of delirium and neuroimaging correlates of post-transplant delirium in a retrospective cohort of 115 adults undergoing neuroimaging after allogeneic HCT. Delirium was established using previously validated methods for retrospective identification of chart-assessed postprocedural delirium. Chart reviews were independently conducted by a multidisciplinary team with expertise in HCT, psychiatry, and psychology on consecutive allogeneic HCT patients who underwent neuroimaging assessments and transplantation at a single center between January 2009 and December 2016. Neuroimaging markers of white matter damage and brain volume loss were also recorded. In total, 115 patients were included, ranging in age from 20 to 74 years (mean [SD] age, 49 [13]). Fifty-three patients (46%) developed post-HCT delirium. In an adjusted model, delirium incidence was associated with older age (odds ratio [OR], 1.92 [1.28, 2.87] per decade, P = .002), greater severity of white matter hyperintensities (OR, 1.95 [1.06, 3.57], P = .031), and conditioning intensity (OR, 6.37 [2.20, 18.45], P < .001) but was unrelated to cortical atrophy (P = .777). Delirium was associated with fewer hospital-free days (P = .023) but was not associated with overall survival (hazard ratio, 0.95 [0.56, 1.61], P = .844). Greater incidence of delirium following HCT was associated with greater age, microvascular burden, and conditioning intensity. Pre-HCT consideration of microvascular burden and other neuroimaging biomarkers of risk may be warranted.

The role of nicotinic cholinergic neurotransmission in delusional thinking

Delusions are a difficult-to-treat and intellectually fascinating aspect of many psychiatric illnesses. Although scientific progress on this complex topic has been challenging, some recent advances focus on dysfunction in neural circuits, specifically in those involving dopaminergic and glutamatergic neurotransmission. Here we review the role of cholinergic neurotransmission in delusions, with a focus on nicotinic receptors, which are known to play a part in some illnesses where these symptoms appear, including delirium, schizophrenia spectrum disorders, bipolar disorder, Parkinson, Huntington, and Alzheimer diseases. Beginning with what we know about the emergence of delusions in these illnesses, we advance a hypothesis of cholinergic disturbance in the dorsal striatum where nicotinic receptors are operative. Striosomes are proposed to play a central role in the formation of delusions. This hypothesis is consistent with our current knowledge about the mechanism of action of cholinergic drugs and with our abstract models of basic cognitive mechanisms at the molecular and circuit levels. We conclude by pointing out the need for further research both at the clinical and translational levels.

Sepsis Associated Delirium

Sepsis is a potentially life-threatening condition caused by a systemic dysregulated host response to infection. The brain is particularly susceptible to the effects of sepsis with clinical manifestations ranging from mild confusion to a deep comatose state. Sepsis-associated delirium (SAD) is a cerebral manifestation commonly occurring in patients with sepsis and is thought to occur due to a combination of neuroinflammation and disturbances in cerebral perfusion, the blood brain barrier (BBB) and neurotransmission. The neurological impairment associated with SAD can persist for months or even longer, after the initial septic episode has subsided which may impair the rehabilitation potential of sepsis survivors. Early identification and treatment of the underlying sepsis is key in the management of SAD as once present it can be difficult to control. Through the regular use of validated screening tools for delirium, cases of SAD can be identified early; this allows potentially aggravating factors to be addressed promptly. The usefulness of biomarkers, neuroimaging and electroencephalopathy (EEG) in the diagnosis of SAD remains controversial. The Society of Critical Care Medicine (SCCM) guidelines advise against the use of medications to treat delirium unless distressing symptoms are present or it is hindering the patient’s ability to wean from organ support.

Evaluating Mechanisms of Postoperative Delirium and Cognitive Dysfunction Following Elective Spine Surgery in Elderly Patients (CONFESS): Protocol for a Prospective Observational Trial

Background

Elderly people are at particular high risk for postoperative delirium (POD) following spine surgery, which is associated with longer hospital stays, higher costs, risk for delayed complications, long-term care dependency, and cognitive dysfunction (POCD). It is insufficiently understood which mechanisms and risk factors contribute to the development of POD and POCD following these major but plannable surgeries.

Objective

This study aims to identify modifiable risk factors in spine surgery. A better understanding thereof would help adapt medical management and surgical strategies to individual risk profiles.

Methods

This is a single-center observational study jointly conducted by the departments of neurosurgery, neurology, and anesthesiology at a tertiary care hospital in Germany. All patients aged 60 years and older presenting to the neurosurgery outpatient clinic or ward for elective spine surgery are screened for eligibility. Exclusion criteria include presence of neurodegenerative or history of psychiatric disease and medication with significant central nervous system activity (eg, antidepressants, antipsychotics, sedatives). Surgical and anesthetic procedures including duration of surgery as primary end point of this study are thoroughly documented. All patients are furthermore evaluated for their preoperative cognitive abilities by a number of tests, including the Consortium to Establish a Registry for Alzheimer's Disease Plus test battery. Physical, mental, and social health and well-being are assessed using the Patient-Reported Outcome Measurement Information System Profile 29 and Hospital Anxiety and Depression Scale. Patients additionally receive preoperative cerebrovascular ultrasound and structural and functional brain imaging. The immediate postoperative period includes screening for POD using the Nursing Delirium Screening Scale and validation through Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, criteria. We furthermore investigate markers of (neuro)inflammation (eg, interleukins, C-reactive protein, tumor necrosis factor alpha). Preoperative examinations are repeated 3 months postoperatively to investigate the presence of POCD and its mechanisms. Statistical analyses will compare delirious and nondelirious patients for predictors of immediate (POD) and delayed (POCD) cognitive dysfunction.

Results

This is the first study to prospectively evaluate risk factors for POD and POCD in spine surgery. Recruitment is ongoing, and data collection is estimated to be finished with the inclusion of 200 patients by mid-2020.

Conclusions

The identification of mechanisms, possibly common, underlying POD and POCD would be a major step toward defining effective interventional strategies early in or even before the postoperative period, including the adaptation of surgical strategies to individual risk profiles.

Trial Registration

ClinicalTrials.gov NCT03486288; https://clinicaltrials.gov/ct2/show/NCT03486288

Cortical and subcortical changes in resting-state functional connectivity before and during an episode of postoperative delirium

OBJECTIVE

Delirium is an acute brain failure related to uncertain problems in neural connectivity, including aberrant functional interactions between remote cortical regions. This study aimed to elucidate the underlying neural mechanisms of delirium by clarifying the changes in resting-state functional connectivity induced by postoperative delirium using imaging data scanned before and after surgery.

METHOD

Fifty-eight patients with a femoral neck fracture were preoperatively scanned using resting-state functional magnetic resonance imaging. Twenty-five patients developed postoperative delirium, and 14 of those had follow-up scans during delirium. Eighteen patients without delirium completed follow-up scans 5 or 6 days after surgery. We assessed group differences in voxel-based connectivity, in which the seeds were the posterior cingulate cortex, medial prefrontal cortex and 11 subcortical regions. Connections between the subcortical regions were also examined.

RESULTS

The results showed four major findings during delirium. Both the posterior cingulate cortex and medial prefrontal cortex were strongly connected to the dorsolateral prefrontal cortex. The posterior cingulate cortex had hyperconnectivity with the inferior parietal lobule, whereas the medial prefrontal cortex had hyperconnectivity with the frontopolar cortex and hypoconnectivity with the superior frontal gyrus. Connectivity of the striatum with the anterior cingulate cortex and insula was increased. Disconnections were found between the lower subcortical regions including the neurotransmitter origins and the striatum/thalamus in the upper level.

CONCLUSIONS

Our findings suggest that cortical dysfunction during delirium is characterized by a diminution of the anticorrelation between the default mode network and task-positive regions, excessive internal connections in the posterior default mode network and a complex imbalance of internal connectivity in the anterior default mode network. These dysfunctions can be attributed to the loss of reciprocity between the default mode network and central executive network associated with defective function in the salience network, which might be closely linked to aberrant subcortical neurotransmission-related connectivity and striato-cortical connectivity.

Structural Brain Changes in Delirium: An Integrative Review

Delirium is a serious complication of acute illness. Little is known, however, regarding the neurobiology of delirium, largely due to challenges in studying the complex inpatient population. Neuroimaging is one noninvasive method that can be used to study structural and functional brain abnormalities associated with delirium. The purpose of this integrative literature review was to examine the content and quality of current structural neuroimaging evidence in delirium. After meeting inclusion criteria, 11 articles were included in the review. Commonly noted structural abnormalities were impaired white matter integrity, brain atrophy, ischemic lesions, edema, and inflammation. Findings demonstrated widespread alterations in several brain structures. Limitations of the studies in this review included small sample sizes, inappropriate or questionable delirium measurements, and failure to consider confounding variables. This review provides insight into possible structural changes responsible for the signs and symptoms seen in patients with delirium, but more high-quality studies are needed.

The Life Course Health Development Model: A theoretical research framework for paediatric delirium

AIMS AND OBJECTIVES

To create a framework for future research through application and critique of the Life Course Health Development Model to the phenomenon of paediatric delirium.

BACKGROUND

Delirium in the paediatric intensive care unit is associated with increased duration of mechanical ventilation, length of stay and mortality. Nurses are uniquely positioned at the bedside to identify, prevent and treat delirium. An understanding of the potential long-term consequences of paediatric delirium is necessary to provide impetus for nursing research and practice change. The Life Course Health Development Model is a valuable tool when considering the multiple mechanisms and processes through which the experience of delirium could affect a child's life trajectory.

DESIGN

Critical review of the literature through application and critique of the Life Course Health Development Model in the context of paediatric delirium. Gaps in the current understanding of paediatric delirium, as well as future directions for research and practice, are discussed.

METHODS

The seven core principles of the model are considered in the context of paediatric delirium. Each of the principles has the potential to further understanding of paediatric delirium and identify areas for future inquiry. This discussion leads to a critique of the ability of the model to lead future research and practice change.

CONCLUSIONS

The Life Course Health Development Model depicts a process in which the acute and severe stress of critical illness leads to maladaptive neurologic changes that contribute to the development of delirium and impair a child's life trajectory.

RELEVANCE TO CLINICAL PRACTICE

By emphasising the potential lifelong consequences for critically ill children who experience delirium, this application of the Life Course Health Development Model will stimulate discussion, research and practice change among paediatric clinicians and researchers.

Delirium is associated with frequency band specific dysconnectivity in intrinsic connectivity networks: preliminary evidence from a large retrospective pilot case-control study

Background

Pathophysiological concepts in delirium are not sufficient to define objective biomarkers suited to improve clinical approaches. Advances in neuroimaging have revalued electroencephalography (EEG) as a tool to assess oscillatory network activity in neuropsychiatric disease. Yet, research in the field is limited to small populations and largely confined to postoperative delirium, which impedes generalizability of findings and planning of prospective studies in other populations. This study aimed to assess effect sizes of connectivity measures in a large mixed population to demonstrate that there are measurable EEG differences between delirium and control patients.

Methods

This retrospective pilot study investigated EEG measures as biomarkers in delirium using a case-control design including patients diagnosed with delirium (DSM-5 criteria) and age-/gender-matched controls drawn from a database of 9980 patients (n = 129 and 414, respectively). Assessors were not blinded for groups. Power spectra and connectivity estimates, using the weighted phase log index, of continuous EEG data were compared between conditions. Alterations of information flow through nodes of intrinsic connectivity networks (ICN; default mode, salience, and executive control network) were evaluated in source space using betweenness centrality. This was done frequency specific and network nodes were defined by the multimodal human cerebral cortex parcellation based on human connectome project data.

Results

Delirium and control patients exhibited distinct EEG power, connectivity, and network characteristics (F_(72,540) = 70.3, p < .001; F_(493,1079) = 2.69, p < .001; and F_(718,2159) = 1.14, p = .007, respectively). Connectivity analyses revealed global alpha and regional beta band disconnectivity that was accompanied by theta band hyperconnectivity in delirious patients. Source and network analyses yielded that these changes are not specific to single intrinsic connectivity networks but affect multiple nodes of networks engaged in level of consciousness, attention, working memory, executive control, and salience detection. Effect sizes were medium to strong in this mixed population of delirious patients.

Conclusions

We quantified effect sizes for EEG connectivity and network analyses to be expected in delirium. This study implicates that theta band hyperconnectivity and alpha band disconnectivity may be essential mechanisms in the pathophysiology of delirium. Upcoming prospective studies will build upon these results and evaluate the clinical utility of identified EEG measures as therapeutic and prognostic biomarkers.

Electronic supplementary material

The online version of this article (10.1186/s40814-018-0388-z) contains supplementary material, which is available to authorized users.

Reconceptualizing delirium as a disorder of complex system failure

Delirium is conceptually elusive and falls outside of conventional biomedical models. Positivist theoretical paradigms of single linear causality are therefore insufficient to provide mechanistic enlightenment. Delirium does, however, share parallels with features of failure within a complex system. Lessons from complex system theory provide important potential healthcare dividends with respect to delirium. The brain is complex and exhibits emergence, a feature of consciousness, which is crucially impacted in delirium. Volatility, non-linear relationships and multiple point failures are cardinal features of complex system failure, thence delirium. An alternative emphasis away from end of chain analysis and oversimplification of cause and an attempt to avoid introduction of new forms of failure in a responsive healthcare environment are lessons from complex system theory. Insights from complex systems provide potentially important mechanistic underpinnings and new lines of research enquiry for delirium. Not least, a fuller understanding of delirium from a complex system viewpoint may help transform management and outcomes in one of the biggest challenges of acute healthcare.