Cognitive impairment after liver transplantation: residual hepatic encephalopathy or posttransplant encephalopathy?

Reversibility of structural and functional alterations of hepatic encephalopathy

Hepatic Encephalopathy (HE) is a frequent complication of chronic liver disease. Type C HE mainly appears in episodes; only seldom chronic persistent forms occur. HE can lead to hospitalization and it has a huge impact on the health related quality of life. Symptoms of HE comprise alterations of the mental status and HE was associated with structural brain alterations. After the resolution of HE episodes alterations of the mental status seem to be reversible. However, cognitive impairment was described to persist in some patients in between HE episodes questioning the full reversibility of functional and structural alterations of HE. The causative treatment of chronic liver disease and subsequent HE episodes is liver transplantation. After liver transplantation functional and structural alterations caused by HE seem to be reversible, however, neurological complications in the first weeks after liver transplantation are frequent, especially in patients with a history of HE before transplantation. Furthermore, in patients in the long term after liver transplantation cognitive dysfunction was described. The underlying causes discussed are residual HE, side effects of immunosuppressive therapy and cerebrovascular disease besides others. It is an important question for patients and caregivers whether HE is a fully reversible episodic phenomenon or if it leads to persistent structural and functional brain alterations even after liver transplantation.

A Comparative Study of Cognitive and Motor Performance in Liver Recipients

Introduction: Neurocognitive and motor impairments are often observed both before and after liver transplantation, resulting in inefficiencies in dual-task performance. Specific aim: The aim of this study was to evaluate the motor-cognitive dual-task performance in liver recipients, with a particular emphasis on cognition, performance status, and the impact of the COVID-19 pandemic. Design: A prospective, cross-sectional, web-based design with a control group was used. The study included 22 liver transplant recipients and 23 controls. Participants completed a motor-cognitive dual-task test (timed up and go test, TUG), a cognitive assessment (mini mental state examination), and a physical performance test (5-repetition sit-to-stand test). The study also used a functional performance status scale (The Karnofsky performance status) and assessed fear of coronavirus disease (fear of COVID-19 scale). Dual-task interference was assessed and the rate of correct responses per second was calculated to assess cognitive performance. Results: The results indicated no statistically significant difference in TUG time and TUG correct responses per second between the groups (group × condition interactions; P > 0.05). There was no significant difference in cognitive and motor dual-task interference during the TUG test between the two groups (P > 0.05). The Karnofsky Performance Status score was significantly correlated with TUG motor dual-task interference (r = -0.424 and P = 0.049). Conclusion: This study suggests that dual-task performance does not differ in cognitive or motor performance between liver recipients and healthy controls under the same dual-task condition. However, further controlled studies are needed to improve the generalizability of these findings.

Prevalence of Minimal Hepatic Encephalopathy in Patients With Liver Cirrhosis: A Multicenter Study

INTRODUCTION

The prevalence of minimal hepatic encephalopathy (MHE), in particular in different subgroups, remains unknown. This study aimed to analyze the prevalence of MHE in different subgroups to identify patients at high risk and to pave the way for personalized screening approaches.

METHODS

In this study, data of patients recruited at 10 centers across Europe and the United States were analyzed. Only patients without clinical signs of hepatic encephalopathy were included. MHE was detected using the Psychometric Hepatic Encephalopathy Score (PHES, cut-off < or ≤-4 depending on local norms). Clinical and demographic characteristics of the patients were assessed and analyzed.

RESULTS

In total, 1,868 patients with cirrhosis with a median model for end-stage liver disease (MELD) of 11 were analyzed (Child-Pugh [CP] stages: A 46%, B 42%, and C 12%). In the total cohort, MHE was detected by PHES in 650 patients (35%). After excluding patients with a history of overt hepatic encephalopathy, the prevalence of MHE was 29%. In subgroup analyses, the prevalence of MHE in patients with CP A was low (25%), whereas it was high in CP B or C (42% and 52%). In patients with a MELD score <10, the prevalence of MHE was only 25%, but it was 48% in patients with a MELD score ≥20. Standardized ammonia levels (ammonia level/upper limit of normal of each center) correlated significantly, albeit weakly with PHES (Spearman ρ = -0.16, P < 0.001).

DISCUSSION

The prevalence of MHE in patients with cirrhosis was high but varied substantially between diseases stages. These data may pave the way for more individualized MHE screening approaches.

Cognitive function, self-management, and outcomes among liver transplant recipients: LivCog, a multicenter, prospective study

Liver transplantation is a life-saving option for decompensated cirrhosis. Liver transplant recipients require advanced self-management skills, intact cognitive skills, and care partner support to improve long-term outcomes. Gaps remain in understanding post-liver transplant cognitive and health trajectories, and patient factors such as self-management skills, care partner support, and sleep. Our aims are to (1) assess pre-liver transplant to post-liver transplant cognitive trajectories and identify risk factors for persistent cognitive impairment; (2) evaluate associations between cognitive function and self-management skills, health behaviors, functional health status, and post-transplant outcomes; and (3) investigate potential mediators and moderators of associations between cognitive function and post-liver transplant outcomes. LivCog is a longitudinal, prospective observational study that will enroll 450 adult liver transplant recipients and their caregivers/care partners. The duration of the study is 5 years with 24 additional months of patient follow-up. Data will be collected from participants at 1, 3, 12, and 24 months post-transplant. Limited pre-liver transplant data will also be collected from waitlisted candidates. Data collection methods include interviews, surveys, cognitive assessments, and actigraphy/sleep diary measures. Patient measurements include sociodemographic characteristics, pretransplant health status, cognitive function, physical function, perioperative measures, medical history, transplant history, self-management skills, patient-reported outcomes, health behaviors, and clinical outcomes. Caregiver measures assess sociodemographic variables, health literacy, health care navigation skills, self-efficacy, care partner preparedness, nature and intensity of care, care partner burden, and community participation. By elucidating various health trajectories from pre-liver transplant to 2 years post-liver transplant, LivCog will be able to better characterize recipients at higher risk of cognitive impairment and compromised self-management. Findings will inform interventions targeting health behaviors, self-management, and caregiver supports to optimize outcomes.

Regulation of mild cognitive impairment associated with liver disease by humoral factors derived from the gastrointestinal tract and MRI research progress: a literature review

Patients with liver disease are prone to various cognitive impairments. It is undeniable that cognitive impairment is often regulated by both the nervous system and the immune system. In this review our research focused on the regulation of mild cognitive impairment associated with liver disease by humoral factors derived from the gastrointestinal tract, and revealed that its mechanisms may be involved with hyperammonemia, neuroinflammation, brain energy and neurotransmitter metabolic disorders, and liver-derived factors. In addition, we share the emerging research progress in magnetic resonance imaging techniques of the brain during mild cognitive impairment associated with liver disease, in order to provide ideas for the prevention and treatment of mild cognitive impairment in liver disease.

Abnormal brain oxygen homeostasis in an animal model of liver disease

Background & Aims

Increased plasma ammonia concentration and consequent disruption of brain energy metabolism could underpin the pathogenesis of hepatic encephalopathy (HE). Brain energy homeostasis relies on effective maintenance of brain oxygenation, and dysregulation impairs neuronal function leading to cognitive impairment. We hypothesised that HE is associated with reduced brain oxygenation and we explored the potential role of ammonia as an underlying pathophysiological factor.

Methods

In a rat model of chronic liver disease with minimal HE (mHE; bile duct ligation [BDL]), brain tissue oxygen measurement, and proton magnetic resonance spectroscopy were used to investigate how hyperammonaemia impacts oxygenation and metabolic substrate availability in the central nervous system. Ornithine phenylacetate (OP, OCR-002; Ocera Therapeutics, CA, USA) was used as an experimental treatment to reduce plasma ammonia concentration.

Results

In BDL animals, glucose, lactate, and tissue oxygen concentration in the cerebral cortex were significantly lower than those in sham-operated controls. OP treatment corrected the hyperammonaemia and restored brain tissue oxygen. Although BDL animals were hypotensive, cortical tissue oxygen concentration was significantly improved by treatments that increased arterial blood pressure. Cerebrovascular reactivity to exogenously applied CO2 was found to be normal in BDL animals.

Conclusions

These data suggest that hyperammonaemia significantly decreases cortical oxygenation, potentially compromising brain energy metabolism. These findings have potential clinical implications for the treatment of patients with mHE.

Lay summary

Brain dysfunction is a serious complication of cirrhosis and affects approximately 30% of these patients; however, its treatment continues to be an unmet clinical need. This study shows that oxygen concentration in the brain of an animal model of cirrhosis is markedly reduced. Low arterial blood pressure and increased ammonia (a neurotoxin that accumulates in patients with liver failure) are shown to be the main underlying causes. Experimental correction of these abnormalities restored oxygen concentration in the brain, suggesting potential therapeutic avenues to explore.

Subjective Cognition Reported by Caregivers Is Correlated With Objective Cognition in Liver Transplant Recipients

Objective cognitive assessments, a gold standard diagnostic tool for cognitive impairment, may not be feasible in busy liver transplantation (LT) practice because they are often time consuming. This study determined whether subjective cognition, patients' self-ratings and/or caregivers' ratings of patients' cognition, reflects objective cognition in LT recipients. A convenience sample of 60 adult LT recipients and their caregivers, recruited at a single transplant center, participated in this cross-sectional descriptive study. Subjective cognition (ie, recipient self-rated and caregiver rated) was measured using the Everyday Cognition (ECog; global and 6 domain scores). Objective global and domain-specific cognition of recipients was measured using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Trail Making Test parts A and B, Digit Span Backward, and Rey-Osterrieth Complex Figure. Agreement between LT recipients' ECog scores and those of their caregivers was fair to moderate (intraclass correlation coefficient = 0.48 for global score, 0.35-0.56 for domain scores). Significant, albeit rather weak, correlations were found between subjective and objective scores. Recipients' ECog visuospatial abilities scores were correlated with Rey-Osterrieth Complex Figure scores (r_s  = -0.39; P = 0.007), whereas caregivers' ECog global, attention, visuospatial abilities, and organization scores were, respectively, correlated with the scores of RBANS global (r_s  = -0.33; P = 0.04) and attention (r_s  = -0.46; P = 0.005), Rey-Osterrieth Complex Figure (Copy; r_s  = -0.34; P = 0.03), and Trail Making Test part A (r_s  = 0.31; P = 0.049). The findings suggest that caregivers may estimate LT recipients' cognition better than recipients themselves. Caregivers may provide supplemental information that could be useful for clinicians when considering the cognitive functioning of LT recipients.

Hepatic Encephalopathy and Liver Transplantation: The Past, Present, and Future Toward Equitable Access

Cirrhosis is a debilitating chronic disease with high morbidity and mortality, with the only real cure being liver transplantation (LT). Currently, we allocate organs for transplantation based on the Model for End-Stage Liver Disease-Sodium (MELD-Na) score that does not account for hepatic encephalopathy (HE). HE affects patients, families, and the health care system because of high rates of recurrence and major readmission burden. Moreover, HE casts a long shadow even after LT. Accounting for HE and incorporating it into the current allocation system has many proponents, but the framework to do this is currently lacking because of differences in consensus or in operationalization parameters. We review the latest evidence of the burden of HE, management of HE before and after LT, and evaluate pros and cons of several methods of diagnosing HE objectively to ensure early and equitable access to LT in this underserved population.

Renormalization of Thalamic Sub-Regional Functional Connectivity Contributes to Improvement of Cognitive Function after Liver Transplantation in Cirrhotic Patients with Overt Hepatic Encephalopathy

Objective

The role of preoperative overt hepatic encephalopathy (OHE) in the neurophysiological mechanism of cognitive improvement after liver transplantation (LT) remains elusive. This study aimed to explore changes in sub-regional thalamic functional connectivity (FC) after LT and their relationship with neuropsychological improvement using resting-state functional MRI (rs-fMRI) data in cirrhotic patients with and without a history of OHE.

Materials and Methods

A total of 51 cirrhotic patients, divided into the OHE group (n = 21) and no-OHE group (n = 30), and 30 healthy controls were enrolled in this prospective study. Each patient underwent rs-fMRI before and 1 month after LT. Using 16 bilateral thalamic subregions as seeds, we conducted a seed-to-voxel FC analysis to compare the thalamic FC alterations before and after LT between the OHE and no-OHE groups, as well as differences in FC between the two groups of cirrhotic patients and the control group. Correction for multiple comparisons was conducted using the false discovery rate (p < 0.05).

Results

We found abnormally increased FC between the thalamic sub-region and prefrontal cortex, as well as an abnormally decreased FC between the bilateral thalamus in both OHE and no-OHE cirrhotic patients before LT, which returned to normal levels after LT. Compared with the no-OHE group, the OHE group exhibited more extensive abnormalities prior to LT, and the increased FC between the right thalamic subregions and right inferior parietal lobe was markedly reduced to normal levels after LT.

Conclusion

The renormalization of FC in the cortico-thalamic loop might be a neuro-substrate for the recovery of cognitive function after LT in cirrhotic patients. In addition, hyperconnectivity between thalamic subregions and the inferior parietal lobe might be an important feature of OHE. Changes in FC in the thalamus might be used as potential biomarkers for recovery of cognitive function after LT in cirrhotic patients.

Bile-duct ligation renders the brain susceptible to hypotension-induced neuronal degeneration: Implications of ammonia

Hepatic encephalopathy (HE) is a debilitating neurological complication of cirrhosis. By definition, HE is considered a reversible disorder, and therefore HE should resolve following liver transplantation (LT). However, persisting neurological complications are observed in as many as 47% of LT recipients. LT is an invasive surgical procedure accompanied by various perioperative factors such as blood loss and hypotension which could influence outcomes post-LT. We hypothesize that minimal HE (MHE) renders the brain frail and susceptible to hypotension-induced neuronal cell death. Six-week bile duct-ligated (BDL) rats with MHE and respective SHAM-controls were used. Several degrees of hypotension (mean arterial pressure of 30, 60 and 90 mm Hg) were induced via blood withdrawal from the femoral artery and maintained for 120 min. Brains were collected for neuronal cell count and apoptotic analysis. In a separate group, BDL rats were treated for MHE with the ammonia-lowering strategy ornithine phenylacetate (OP; MNK-6105), administered orally (1 g/kg) for 3 weeks before induction of hypotension. Hypotension 30 and 60 mm Hg (not 90 mm Hg) significantly decreased neuronal marker expression (NeuN) and cresyl violet staining in the frontal cortex compared to respective hypotensive SHAM-operated controls as well as non-hypotensive BDL rats. Neuronal degeneration was associated with an increase in cleaved caspase-3, suggesting the mechanism of cell death was apoptotic. OP treatment attenuated hyperammonaemia, improved anxiety and activity, and protected the brain against hypotension-induced neuronal cell death. Our findings demonstrate that rats with chronic liver disease and MHE are more susceptible to hypotension-induced neuronal cell degeneration. This highlights MHE at the time of LT is a risk factor for poor neurological outcome post-transplant and that treating for MHE pre-LT might reduce this risk.

Cognitive Function in Liver Transplant Recipients Who Survived More Than 6 Months

Introduction:

Current research in the areas of liver transplant and cognitive function has primarily examined cognitive changes from pre- to 1-year posttransplant, resulting in an insufficient understanding of cognitive trajectory beyond early periods of transplant and its impact on self-management. This study aimed (1) to describe global and domain-specific cognitive function in liver transplant recipients who survived more than 6 months after transplant and (2) to describe patient and clinical characteristics of recipients with impaired global and/or domain-specific cognitive function. Further, this study explored the potential relationships between cognitive function and self-management by examining differences in cognitive function by levels of self-management.

Design:

This secondary data analysis included 107 adult liver transplant recipients, who had a functioning transplant for at least 6 months. Data of cognitive function, demographic and clinical characteristics, and self-management were extracted for this study. T tests, Mann-Whitney tests, and Kruskal-Wallis tests were used to examine differences in cognitive function by variables.

Results:

More than half of the recipients had global cognitive impairment. Significant differences were found in global and domain-specific cognitive function. Older, male, married, or deceased donor recipients had lower cognitive test scores than younger, female, single, or living donor recipients. There were no significant differences in global and domain-specific cognitive function by time since transplant and levels of self-management.

Discussion:

Future longitudinal studies should examine the long-term trajectory of cognitive function posttransplant. Other factors such as caregivers’ participation in self-management should be accounted for in future studies when examining the relationship between cognitive function and self-management.