The psychomotor vigilance task: Role in the diagnosis of hepatic encephalopathy and relationship with driving ability

Impaired Vigilance in Patients with Narcolepsy Type 1: A Psychomotor Vigilance Task Study

Purpose

The psychomotor vigilance task (PVT) is one of the main methods to measure sustained vigilance/attention in sleep research. Vigilance is the main factor affecting daytime function in patients with narcolepsy type 1 (NT1). We aimed to quantify the negative effects of sleep-wake disorders on vigilance and investigate potential neural mechanisms.

Patients and Methods

We compared data from 42 patients and 31 healthy controls, including sociodemographics, nighttime sleep quality (Pittsburgh Sleep Quality Index, PSQI), sleepiness (Epworth Sleepiness Scale, ESS), cognitive abilities (Montreal Cognitive Assessment, MoCA), emotional control (Barratt Impulsiveness Scale-11, BIS-11), depressive symptoms (Patient Health Questionnaire-9, PHQ-9), and PVT performance. PVT outcomes analyzed included number of lapses, reaction time (RT), variability in RT, and the slowest and fastest 10% of RTs. All patients were diagnosed with NT1 based on The International Classification of Sleep Disorders-Third Edition.

Results

Patients with NT1 had a significantly higher body mass index and longer duration of education than healthy controls. The patients also had a greater tendency for daytime sleepiness and poorer nighttime sleep quality, higher depression and impulsiveness scores, and more severe cognitive dysfunction. PVT performance was better in the healthy controls than in patients with NT1. We also noticed that emotional changes and the proportion of rapid eye movement sleep at night are related to PVT performance.

Conclusion

More severe sleepiness and an increased emotional burden could underlie the arousal and vigilance deficits seen in patients with NT1. We speculate that impaired vigilance in patients with NT1 is associated with abnormal brain function caused by a resource allocation imbalance related to hypothalamic orexin neuron damage, sleep inertia may also have a slight impact on this. Future studies should delve into this topic more deeply.

Correlation of ammonia and blood laboratory parameters with hepatic encephalopathy: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Emerging research suggests that hyperammonemia may enhance the probability of hepatic encephalopathy (HE), a condition associated with elevated levels of circulating ammonia in patients with cirrhosis. However, some studies indicate that blood ammonia levels may not consistently correlate with the severity of HE, highlighting the complex pathophysiology of this condition.

METHODS

A systematic review and meta-analysis through PubMed, Scopus, Embase, Web of Science, and Virtual Health Library were conducted to address this complexity, analyzing and comparing published data on various laboratory parameters, including circulating ammonia, blood creatinine, albumin, sodium, and inflammation markers in cirrhotic patients, both with and without HE.

RESULTS

This comprehensive review, which included 81 studies from five reputable databases until June 2024, revealed a significant increase in circulating ammonia levels in cirrhotic patients with HE, particularly those with overt HE. Notably, significant alterations were observed in the circulating creatinine, albumin, sodium, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNFα) in HE patients.

CONCLUSIONS

These findings suggest an association between ammonia and HE and underscore the importance of considering other blood parameters such as creatinine, albumin, sodium, and pro-inflammatory cytokines when devising new treatment strategies for HE.

Development and evaluation of a virtual reality driving test for patients with cirrhosis

BACKGROUND

Patients with cirrhosis and especially those with HE may have impaired driving skills and may be prone to car accidents. This proof-of-concept study aimed to develop and evaluate the applicability of a virtual reality (VR)-based driving test in patients with cirrhosis. Additionally, the association between the results in the VR test and car accidents was investigated.

METHODS

A short driving test using a VR head-mounted display (HTC Vive Pro Eye) was developed to simulate five hazardous situations. The patient has to pull the brake when the hazardous situations occur. The time from triggering the event to pressing the brake is recorded as reaction time. Total reaction time (TRT) is defined as the combined reaction time to all 5 events. Car accidents were assessed retrospectively (previous 12 months) and patients were followed prospectively for 6 months. Minimal HE (MHE) was diagnosed using Psychometric Hepatic Encephalopathy Score.

RESULTS

In total, 112 outpatients with cirrhosis and 52 controls without cirrhosis were recruited. MHE was detected in 14% (n = 15). Patients with cirrhosis and MHE (5.67 s) had higher TRTs compared to patients without MHE (5.02 s) and controls without cirrhosis above the age of 50 (4.98 s) (MHE vs. no MHE or controls p<0.01, no MHE vs. controls: not significant). Seven patients reported car accidents during the twelve months prior to study inclusion. TRTs were numerically higher in patients with reported car accidents (p = 0.099). When patients who stopped driving for HE-related/cirrhosis-related reasons (n = 14) were added to the group of patients with accidents, then a longer TRT was significantly associated with the modeled outcome in univariable (p<0.01) and multivariable analyses (OR 2.83, p<0.01). Two car accidents occurred during follow-up. Both patients had TRTs above the 90th percentile.

CONCLUSIONS

The VR driving test is easy and rapid to perform in patients with cirrhosis and could be helpful as a point-of-care tool for predicting car accidents.

The Assessment of Driving Fitness Using an On-Road Evaluation in Patients With Cirrhosis

INTRODUCTION

The association between cirrhosis and driving performance is of particular clinical relevance because of the life-threatening safety issues both for the driver with cirrhosis and the general public. Study aims were to assess (i) driving competency through the use of an in-office computerized battery and on-road driving assessment (DriveABLE) and (ii) the association between minimal hepatic encephalopathy (MHE), in-office paper-pencil tools, and additional measures (e.g., frailty, depression, cognitive testing) with unsafe driving.

METHODS

Patients were prospectively recruited from 2 tertiary care liver clinics. In-office tests and in-office and on-road assessments of driving competence were completed. The χ 2 test and 1-way analysis of variance were used to analyze differences among those with and without MHE. Logistic regression was used to evaluate predictors of an indeterminate/fail result on the in-office computerized driving assessment battery (DriveABLE Cognitive Assessment Tool [DCAT]).

RESULTS

Eighty patients participated with a mean age of 57 years, 70% male, 75% Child-Pugh B/C, and 36% with a history of overt hepatic encephalopathy. Thirty percent met MHE criteria on both the psychometric hepatic encephalopathy score and the Stroop app tests. Only 2 patients (3%) were categorized as "unfit to drive" in the on-road driving test, one with MHE and the other without. Fifty-eight percent of the patients were scored as indeterminate/fail on the DCAT. This corresponded to a higher mean number of on-road driving errors (5.3 [SD 2.1] vs 4.2 [SD 1.6] in those who passed the DCAT, P = 0.01). Older age (odds ratio 1.3; confidence interval 1.1, 1.5; P = 0.001) and MHE by Stroop/psychometric hepatic encephalopathy score (odds ratio 11.0; confidence interval 2.3, 51.8; P = 0.002) were independently predictive of worse performance on the DCAT.

DISCUSSION

Worse performance in in-office testing was associated with worse scores on a computerized driving assessment battery and more on-road driving errors, but in-office tools were insufficient to predict on-road driving failures. A diagnosis of MHE should not be used alone to restrict driving in patients with cirrhosis. At-risk patients require on-road driving tests under the supervision of driving regulatory agencies. Future studies should continue to refine and evaluate in-office or at-home testing to predict driving performance.

Psychometric methods for diagnosing and monitoring minimal hepatic encephalopathy -current validation level and practical use

Hepatic encephalopathy (HE) is cerebral dysfunction caused by liver failure and inflicts 30-40% of patients with liver cirrhosis during their disease course. Clinically manifest HE is often preceded by minimal HE (MHE) - a clinically undetectable cognitive disturbance closely associated with loss of quality of life. Accordingly, detecting and treating MHE improve the patients' daily functioning and prevent HE-related hospital admissions. The scope of this review article is to create an overview of the validation level and usage of psychometric tests used to detect MHE: Portosystemic hepatic encephalopathy test, continuous reaction time test, Stroop EncephalApp, animal naming test, critical flicker frequency test, and inhibitory control test. Our work is aimed at the clinician or scientist who is about to decide on which psychometric test would fit best in their clinic, cohort, or study. First, we outline psychometric test validation obstacles and requirements. Then, we systematically approach the literature on each test and select well-conducted studies to answer the following questions:• Which percentage of patients with cirrhosis does the test deem as having MHE?• Is the test able to predict clinically manifest HE?• Is there a well-known test-retest variation and inter-observer variation?• Is the test able to detect a treatment response?• Is the test result affected by age, educational level, gender, or comorbidities?

A Field Study on Safety Performance of Apron Controllers at a Large-Scale Airport Based on Digital Tower

The innovative concept of digital tower provides a new solution for reducing the construction and operation costs of airports with adverse natural environments, poor intervisibility conditions, or sparse traffic. However, it leads to changes in the situational awareness of air traffic controllers and to challenges in safety performance. To research the safety performance of apron controllers at a large-scale airport applying a digital tower, a field study was conducted at Baiyun International Airport in Guangzhou, China. In this study, we established a comprehensive index system from the perspective of situational awareness, which provided measurements on the areas of interests, gaze and physiological features, and vigilance of controllers. Three modules were compared: a physical tower module, a digital tower module with a large panoramic screen, and a digital tower module with a small panoramic screen. The differences in the safety performances of apron controllers are discussed in two aspects: adaptability and reliability. The results indicated that the apron controllers at the three modules performed different cognition patterns, but similar cognition effort was paid toward maintaining performance. Furthermore, the significant vigilance decrement of controllers exists between after-duty and before-duty, but with no significant difference among the three modules. In conclusion, apron controllers at a large-scale airport could obtain effective safety performances based on a digital tower that were no less than those from a physical tower.

Effect of Physical Exercise Program Based on Active Breaks on Physical Fitness and Vigilance Performance

The scientific literature has shown the beneficial effects of chronic Physical Exercise (PE) on a wide range of tasks that involve high-order functioning. For this reason, the present study aimed to investigate the effects of active breaks on physical fitness and vigilance performance in high school students through eight weeks of physical training. A total of 42 healthy students (age = 16.50 ± 0.59 years; height = 171.08 ± 8.07 cm; weight = 67.10 ± 13.76 kg) from one Andalusian high school (Spain) were assigned for convenience and matched into two groups, a Control Group (CG) and an Active-Break Group (ABG). The ABG performed two active breaks (based on strength and self-loading exercises) during the school day, first at 10:00 a.m. and second at 12:30 p.m. The participants were assessed before and after the training program using the Alpha-Fitness test battery and the Psychomotor Vigilance Task (PVT). Significant differences were observed in the post-training PVT results, compared with the pretraining PVT, showing ABG responding faster than CG. Thus, the presents study demonstrated that eight weeks of physical training affects vigilance performance (compared to CG) and improves the efficiency of vigilance in high school students, contributing to enhancement of quality of education.

Learning Generalized Representations of EEG between Multiple Cognitive Attention Tasks

Attention can be measured by different types of cognitive tasks, such as Stroop, Eriksen Flanker, and Psychomotor Vigilance Task (PVT). Despite the differing content of the three cognitive tasks, they all require the use of visual attention. To learn the generalized representations from the electroencephalogram (EEG) of different cognitive attention tasks, extensive intra and inter-task attention classification experiments were conducted on three types of attention task data using SVM, EEGNet, and TSception. With cross-validation in intra-task experiments, TSception has significantly higher classification accuracies than other methods, achieving 82.48%, 88.22%, and 87.31% for Stroop, Flanker, and PVT tests respectively. For inter-task experiments, deep learning methods showed superior performance over SVM with most of the accuracy drops not being significant. Our experiments indicate that there is common knowledge that exists across cognitive attention tasks, and deep learning methods can learn generalized representations better.

The role of astrocytes in generating circadian rhythmicity in health and disease

Evidence is accumulating that the mammalian circadian clock system is considerably more complex than previously believed, also in terms of the cell types that actually contribute to generating the oscillation within the master clock, in the suprachiasmatic nuclei of the hypothalamus. Here we review the evidence that has lead to the identification of a bona fide astrocytic circadian clock, and that of the potential contribution of such clock to the generation of circadian and seasonal rhythmicity in health and in neurodegenerative disorders. Finally, we speculate on the role of the astrocytic clock in determining some of the clinical features of hepatic encephalopathy, a reversible neuropsychiatric syndrome associated with advanced liver disease, which is characterized by transient, profound morphological and functional astrocytic abnormalities, in the absence of significant, structural neuronal changes.

Important Unresolved Questions in the Management of Hepatic Encephalopathy: An ISHEN Consensus

Management of hepatic encephalopathy (HE) remains challenging from a medical and psychosocial perspective. Members of the International Society for Hepatic Encephalopathy and Nitrogen Metabolism recognized 5 key unresolved questions in HE management focused on (i) driving, (ii) ammonia levels in clinical practice, (iii) testing strategies for covert or minimal HE, (iv) therapeutic options, and (v) nutrition and patient-reported outcomes. The consensus document addresses these topical issues with a succinct review of the literature and statements that critically evaluate the current science and practice, laying the groundwork for future investigations.

Minimal Hepatic Encephalopathy

Minimal hepatic encephalopathy, previously called subclinical hepatic encephalopathy, represents the earliest and mildest form of hepatic encephalopathy. It is the most under-recognized and underdiagnosed form of hepatic encephalopathy. Although there is no diagnostic gold standard, validated testing modalities have been devised to detect this neurocognitive complication. The newest developments include medically related apps for smartphones or tablets that can be easily used to diagnose and monitor minimal hepatic encephalopathy. Although recognition of this neurocognitive impairment can be challenging, early detection is paramount with the discovery of an association with worse clinical outcomes in patients diagnosed with minimal hepatic encephalopathy.

Peripheral inflammation induces neuroinflammation that alters neurotransmission and cognitive and motor function in hepatic encephalopathy: Underlying mechanisms and therapeutic implications

Several million patients with liver cirrhosis suffer minimal hepatic encephalopathy (MHE), with mild cognitive and coordination impairments that reduce their quality of life and life span. Hyperammonaemia and peripheral inflammation act synergistically to induce these neurological alterations. We propose that MHE appearance is because of the changes in peripheral immune system, which are transmitted to brain, leading to neuroinflammation that alters neurotransmission leading to cognitive and motor alterations. We summarize studies showing that MHE in cirrhotic patients is associated with alterations in the immune system and that patients died with HE show neuroinflammation in cerebellum, with microglial and astrocytic activation and Purkinje cell loss. We also summarize studies in animal models of MHE on the role of peripheral inflammation in neuroinflammation induction, how neuroinflammation alters neurotransmission and how this leads to cognitive and motor alterations. These studies identify therapeutic targets and treatments that improve cognitive and motor function. Rats with MHE show neuroinflammation in hippocampus and altered NMDA and AMPA receptor membrane expression, which impairs spatial learning and memory. Neuroinflammation in cerebellum is associated with altered GABA transporters and extracellular GABA, which impair motor coordination and learning in a Y maze. These alterations are reversed by treatments that reduce peripheral inflammation (anti-TNFα, ibuprofen), neuroinflammation (sulphoraphane, p38 inhibitors), GABAergic tone (bicuculline, pregnenolone sulphate) or increase extracellular cGMP (sildenafil or cGMP). The mechanisms identified would also occur in other chronic diseases associated with inflammation, aging and some mental and neurodegenerative diseases. Treatments that improve MHE may also be beneficial to treat these pathologies.