Critical flicker frequency for quantification of low-grade hepatic encephalopathy

Comparison of 6 tests for diagnosing minimal hepatic encephalopathy and predicting clinical outcome: A prospective, observational study

BACKGROUND AND AIMS

Current guidelines recommend the assessment for minimal HE in patients with liver cirrhosis. Various efforts were made to find tools that simplify the diagnosis. Here, we compare the 6 most frequently used tests for their validity and their predictive value for overt hepatic encephalopathy (oHE), rehospitalization, and death.

APPROACH AND RESULTS

One hundred thirty-two patients with cirrhosis underwent the Portosystemic Encephalopathy-Syndrome-Test yielding the psychometric hepatic encephalopathy score (PHES), Animal Naming Test (ANT), Critical Flicker Frequency (CFF), Inhibitory Control Test (ICT), EncephalApp (Stroop), and Continuous Reaction Time Test (CRT). Patients were monitored for 365 days regarding oHE development, rehospitalization, and death. Twenty-three patients showed clinical signs of HE grade 1-2 at baseline. Of the remaining 109 neurologically unimpaired patients, 35.8% had abnormal PHES and 44% abnormal CRT. Percentage of abnormal Stroop (79.8% vs. 52.3%), ANT (19.3% vs. 51.4%), ICT (28.4% vs. 36.7%), and CFF results (18.3% vs. 25.7%) changed significantly when adjusted norms were used for evaluation instead of fixed cutoffs. All test results correlated significantly with each other ( p <0.05), except for CFF. During follow-up, 24 patients developed oHE, 58 were readmitted to the hospital, and 20 died. Abnormal PHES results were linked to oHE development in the multivariable model. No other adjusted test demonstrated predictive value for any of the investigated endpoints.

CONCLUSIONS

Where applicable, the diagnosis of minimal HE should be made based on adjusted norm values for the tests, exclusively. The minimal HE tests cannot be equated with one another and have an overall limited value in predicting clinical outcomes.

Other causes of neurocognitive impairment than covert hepatic encephalopathy (CHE) are very frequent, either alone or associated with CHE, in cirrhotic patients with cognitive complaints

BACKGROUND/AIMS

Although it is well admitted that cirrhotic patients display various causes of neurocognitive impairment (NI) hampering the diagnosis of covert hepatic encephalopathy (CHE), those are almost never investigated per se. The aims of this study were, in cirrhotic patients displaying cognitive complaints explored by a complete multimodal work-up, to assess: (1) the prevalence of CHE and/or that of other causes of NI and (2) their outcomes, according to the cause of NI.

METHODS

Prospective cohort of cirrhotic patients referred in a dedicated clinic because of cognitive complaints. Work-up included a complete neuropsychological assessment, electroencephalogram (EEG) and brain magnetic resonance imaging with spectroscopy. The diagnosis of CHE was made by an adjudication committee involving the physicians/neuropsychologist.

RESULTS

One hundred and twenty-three patients were included (alcohol/MASLD/virus in 63/53/14%, MELD = 11). Sixty-six per cent of them were diagnosed with CHE; among them, 73% exhibited also other causes of NI, mainly cerebrovascular diseases/psychiatric. Among patients without CHE, 48% and 59% displayed pathological Psychometric Hepatic Encephalopathy Score and animal naming test, respectively. Clinical improvement was observed in 77% of the patients re-evaluated after specific management. CHE, but not the other causes of NI, was independently associated with OHE occurrence.

CONCLUSION

Other causes of NI than CHE are frequent in patients with cirrhosis, and not ruled-out by the classical tests dedicated to CHE. Prognosis was influenced by the cause of NI. The management of patients even without CHE led to clinical improvement, underlining the need for a multifaceted approach of cirrhotic patients with cognitive complaints.

Hepatic Encephalopathy: Clinical Manifestations

Hepatic encephalopathy (HE) can occur as a complication of chronic liver disease as well as acute liver failure. HE is associated with significantly increased morbidity and worse patient outcomes. The clinical manifestation of HE ranges from early less-severe presentations that may only be accurately detected on dedicated psychomotor diagnostic testing to overt alterations in cognition and mental status to the most severe form of coma. Greater awareness of the clinical manifestations of HE across the spectrum of symptom severity is critical for early identification and timely initiation of appropriate therapy to improve patient outcomes.

Critical flicker fusion in patients with epilepsy under antiseizure medication

OBJECTIVE

Critical flicker frequency (CFF) and flicker frequency (FF) are used as indicators for the neurotoxic adverse events of drugs in pharmacology. In this pilot study, we investigated whether patients with epilepsy (PWE) treated with various antiseizure medications (ASM) had significantly different CFFs compared with healthy controls. In addition, we investigated the appropriateness of CFF as an objective measurement tool in PWE who reported adverse events according to the adverse event profile (AEP).

METHODS

Patients receiving regular antiseizure treatment at our center, along with healthy controls, were included in this study. Clinical neurotoxic symptoms, AEP scores, and serum ASM levels were assessed in the PWE group. We used a CFF device that produced a red-black, green-black, blue-black, or white-black flicker. CFF and FF were compared between PWE and healthy controls. In PWE, the correlation of alterations in CFF and FF with AEP results and through ASM serum concentrations was calculated.

RESULTS

A total of 33 PWE and 20 healthy controls participated in the study. Except for two light modalities, CFF and FF were significantly reduced in PWE compared with controls. CFF and FF did not differ significantly between PWE with AEP scores >44 points and those with lower scores. CFF and FF levels did not correlate with changes in AEP scores, serum concentrations, or doses.

SIGNIFICANCE

CFF and FF distinguished PWE with ASM from healthy controls. No clinically relevant differentiation was detected in the heterogenous PWE group. To investigate whether CFF and FF may serve as subtle indicators of neurotoxicity or specific modes of action, additional studies are needed in more homogenous PWE groups.

Subclinical Cognitive Impairment in Chronic Pancreatitis Is Associated With Reduced Mobility and Quality of Life

INTRODUCTION

This study explores how chronic pancreatitis (CP) relates to subclinical cognitive impairment (SCI) and its prevalence, characteristics, risk factors, and effects on patients' quality of life (QoL) and physical performance.

METHODS

Patients with fulfilled CP criteria in imaging were prospectively enrolled. Overt encephalopathy, neurodegenerative disorders, decompensated cirrhosis, and sepsis were exclusion criteria. All patients underwent psychometric testing and assessment of health-related QoL, such as mobility and strength. SCI was diagnosed when at least 1 test of the psychometric test battery was pathological.

RESULTS

Seventy-one patients were enrolled. The etiology was toxic (alcohol/smoking) in most (49%) of the cases. SCI was prevalent in 41% of the patients while 25% had only 1 and 16% had 2 or more pathological tests. Patients with SCI exhibited diminished overall QoL scores ( P = 0.048), primarily affecting physical functionality ( P < 0.001). This was reaffirmed in mobility tests, where patients with SCI were slower in the timed up-and-go test ( P = 0.008) and showed increased prevalence of abnormal chair rising tests ( P = 0.004). Among all variables analyzed, only alcohol abuse was an independent risk factor of SCI (odds ratio 3.46; P = 0.02) in a multivariable regression model together with the variables age, sex, education, and compensated cirrhosis. Despite SCI affecting global QoL, sleep disturbance seemed to be the strongest variable independently associated with impaired QoL (odds ratio 9.9; P = 0.001).

DISCUSSION

The largest study to the subject to date shows that SCI is common in patients with CP and is linked to significant morbidity. These findings suggest the need for addressing modifiable risk factors in patients with CP to improve outcomes.

The assessment and management of cirrhotic patients with encephalopathy

Hepatic encephalopathy (HE) is a debilitating complication associated with both acute and chronic liver injury. It is associated with a greater risk of death than any other significant hepatic decompensation event. It manifests as a wide spectrum of neuropsychological abnormalities ranging from subtle impairments in higher cognitive function, to confusion and coma. The pathophysiological role of ammonia in the development of HE is well known, but there is increasing recognition that the gut microbiome, gut-derived systemic inflammation and development of infection can serve as drivers of HE in patients with cirrhosis. The development of HE portents to the severity of cirrhosis and the prognosis is poor without liver transplantation. A referral for liver transplantation should therefore be considered early in those who are eligible. This review covers the pragmatic assessment of HE in patients with cirrhosis, as well as the current evidence base for the best practice management of HE in such patients.

Nutritional therapy for persistent cognitive impairment after resolution of overt hepatic encephalopathy in patients with cirrhosis: A double-blind randomized controlled trial

BACKGROUND AND AIM

Minimal hepatic encephalopathy (MHE) reflects cognitive impairment in patients with liver cirrhosis and is associated with poor prognosis. We assessed the effects of nutritional therapy on cognitive functions, health-related quality of life (HRQOL), anthropometry, endotoxins, and inflammatory markers in cirrhotic patients with MHE.

METHODS

In a double-blind randomized controlled trial, cirrhotic patients with MHE were randomized to nutritional therapy (group I: 30-35 kcal/kg/day and 1.0-1.5 g of protein/kg/day) and no nutritional therapy (group II: diet as patients were taking before) for 6 months. MHE was diagnosed based on psychometric hepatic encephalopathy score (PHES). Anthropometry, ammonia, endotoxins, inflammatory markers, myostatin, and HRQOL were assessed at baseline and after 6 months. Primary endpoints were improvement or worsening in MHE and HRQOL.

RESULTS

A total of 150 patients were randomized to group I (n = 75, age 46.3 ± 12.5 years, 58 men) and group II (n = 75, age 45.2 ± 9.3 years, 56 men). Baseline PHES (-8.16 ± 1.42 vs -8.24 ± 1.43; P = 0.54) was comparable in both groups. Reversal of MHE was higher in group I (73.2% vs 21.4%; P = 0.001) than group II. Improvement in PHES (Δ PHES 4.0 ± 0.60 vs -4.18 ± 0.40; P = 0.001), HRQOL (Δ Sickness Impact Profile 3.24 ± 3.63 vs 0.54 ± 3.58; P = 0.001), anthropometry, ammonia, endotoxins, cytokines, and myostatin levels was also significantly higher in group I than group II. Overt hepatic encephalopathy developed in 6 patients in group I and 13 in group II (P = 0.04).

CONCLUSIONS

Nutritional therapy is effective in treatment of MHE and associated with improvement in nutritional status, HRQOL, ammonia, endotoxins, inflammatory markers, and myostatin levels.

Predicting overt hepatic encephalopathy after TIPS: Value of three minimal hepatic encephalopathy tests

Background & Aims

Hepatic encephalopathy (HE) is a frequent and severe complication in patients after transjugular intrahepatic portosystemic shunt (TIPS) insertion. However, risk factors for post-TIPS HE remain poorly defined. Minimal HE (mHE) is a well-known risk factor for overt HE in patients with cirrhosis without TIPS. We aimed to evaluate three tools frequently used for diagnosing mHE for their dynamic changes and their predictive value for overt HE after TIPS.

Methods

We prospectively recruited 84 consecutive patients before TIPS insertion and monitored them for 180 days for post-TIPS HE. Before TIPS insertion, the patients underwent the portosystemic encephalopathy (PSE) syndrome test, the animal naming test (ANT), and the critical flicker frequency (CFF). Patients were retested after TIPS insertion.

Results

The majority of patients were male (67.9%), and the predominant indication for TIPS was refractory ascites (75%). Median age was 59 years, model for end-stage liver disease score was 12, and 66.3%, 64.6%, and 28.4% patients had evidence for mHE according to the PSE syndrome test, ANT, and CFF, respectively. Overall, 25 patients developed post-TIPS HE within 180 days after TIPS insertion. Post-TIPS incidence of overt HE was 22.2, 28.6, 45.5, and 55.6% in those with no, one, two, and three pathological tests at baseline, respectively. However, none of the three tests was significantly associated with post-TIPS HE. Of note, mean performance in all tests remained stable over time after TIPS insertion.

Conclusions

PSE syndrome test, ANT and CFF, which are frequently used for diagnosing mHE have limited value for predicting HE after TIPS insertion. We could not find evidence that TIPS insertion leads to a psychometric decline in the long term.

Impact and implications

This prospective observational study compared three diagnostic tests for mHE and showed the limited value of these tests for predicting overt HE in patients with cirrhosis undergoing TIPS insertion. In addition, the results suggest that cognitive performance generally remains stable after TIPS insertion. These results are important for physicians and researchers involved in the management of patients with cirrhosis undergoing TIPS procedures. The study's findings serve as a starting point for further investigations on the development of more effective strategies for predicting and managing post-TIPS HE.

Clinical trial number

ClinicalTrials.gov NCT04801290.

Influence of NOD2 risk variants on hepatic encephalopathy and association with inflammation, bacterial translocation and immune activation

BACKGROUND

Nucleotide-binding oligomerization domain containing 2 (NOD2) risk variants lead to impaired mucosal barrier function, increased bacterial translocation (BT), and systemic inflammation.

AIM

To evaluate the association between the presence of NOD2 risk variants, BT, inflammation, and hepatic encephalopathy (HE).

PATIENTS AND METHODS

This prospective multicenter study included patients with cirrhosis and testing for NOD2 risk variants (p.R702W, p.G908R, c.3020insC, N289S, and c.-958T>C). Patients were evaluated for covert (C) and overt (O) HE. Markers of systemic inflammation (leukocytes, CRP, IL-6, LBP) and immune activation (soluble CD14) as well as bacterial endotoxin (hTRL4 activation) were determined in serum.

RESULTS

Overall, 172 patients (70% men; median age 60 [IQR 54-66] years; MELD 12 [IQR 9-16]; 72% ascites) were included, of whom 53 (31%) carried a NOD2 risk variant. In this cohort, 11% presented with OHE and 27% and CHE. Presence and severity of HE and surrogates of inflammation, BT, and immune activation did not differ between patients with and without a NOD2 risk variant, also not after adjustment for MELD. HE was associated with increased ammonia and systemic inflammation, as indicated by elevated CRP (w/o HE: 7.2 [2.7-16.7]; with HE 12.6 [4.5-29.7] mg/dL; p < 0.001) and elevated soluble CD14 (w/o HE 2592 [2275-3033]; with HE 2755 [2410-3456] ng/mL; p = 0.025).

CONCLUSIONS

The presence of NOD2 risk variants in patients with cirrhosis is not associated with HE and has no marked impact on inflammation, BT, or immune activation. In contrast, the presence of HE was linked to ammonia, the acute phase response, and myeloid cell activation.

Rifaximin for prevention and treatment of hepatic encephalopathy in people with cirrhosis

BACKGROUND

Hepatic encephalopathy describes the spectrum of neuropsychiatric changes that may complicate the course of cirrhosis and detrimentally affect outcomes. Ammonia plays a key role in its development. Rifaximin is a non-absorbable antibiotic that inhibits urease-producing bacteria and reduces absorption of dietary and bacterial ammonia.

OBJECTIVES

To evaluate the beneficial and harmful effects of rifaximin versus placebo, no intervention, or non-absorbable disaccharides for: (i) the prevention of hepatic encephalopathy, and (ii) the treatment of minimal and overt hepatic encephalopathy, in people with cirrhosis, both when used alone and when combined with a non-absorbable disaccharide.

SEARCH METHODS

We searched the Cochrane Hepato-Biliary Group Clinical Trials Register, CENTRAL, MEDLINE, Embase, three other databases, the reference lists of identified papers, and relevant conference proceedings. We wrote to authors and pharmaceutical companies for information on other published, unpublished, or ongoing trials. Searches were performed to January 2023.

SELECTION CRITERIA

We included randomised clinical trials assessing prevention or treatment of hepatic encephalopathy with rifaximin alone, or with a non-absorbable disaccharide, versus placebo/no intervention, or a non-absorbable disaccharide alone.

DATA COLLECTION AND ANALYSIS

Six authors independently searched for studies, extracted data, and validated findings. We assessed the design, bias risk, and participant/intervention characteristics of the included studies. We assessed mortality, serious adverse events, health-related quality of life, hepatic encephalopathy, non-serious adverse events, blood ammonia, Number Connection Test-A, and length of hospital stay.

MAIN RESULTS

We included 41 trials involving 4545 people with, or at risk for, developing hepatic encephalopathy. We excluded 89 trials and identified 13 ongoing studies. Some trials involved participants with more than one type of hepatic encephalopathy or more than one treatment comparison. Hepatic encephalopathy was classed as acute (13 trials), chronic (7 trials), or minimal (8 trials), or else participants were considered at risk for its development (13 trials). The control groups received placebo (12 trials), no/standard treatment (1 trial), or a non-absorbable disaccharide (14 trials). Eighteen trials assessed rifaximin plus a non-absorbable disaccharide versus a non-absorbable disaccharide alone. We classified 11 trials as at high risk of overall bias for mortality and 28 for non-mortality outcomes, mainly due to lack of blinding, incomplete outcome data, and selective reporting. Compared to placebo/no intervention, rifaximin likely has no overall effect on mortality (risk ratio (RR) 0.83, 95% confidence interval (CI) 0.50 to 1.38; P = 48, I2 = 0%; 13 trials, 1007 participants; moderate-certainty evidence), and there may be no overall effect when compared to non-absorbable disaccharides (RR 0.99, 95% CI 0.49 to 1.97; P = 0.97, I2 = 0%; 10 trials, 786 participants; low-certainty evidence). However, there is likely a reduction in the overall risk of mortality when comparing rifaximin plus a non-absorbable disaccharide to a non-absorbable disaccharide alone (RR 0.69, 95% CI 0.55 to 0.86; number needed to treat for an additional beneficial outcome (NNTB) = 22; P = 0.001, I2 = 0%; 14 trials, 1946 participants; moderate-certainty evidence). There is likely no effect on the overall risk of serious adverse events when comparing rifaximin to placebo/no intervention (RR 1.05, 95% CI 0.83 to 1.32; P = 68, I2 = 0%; 9 trials, 801 participants; moderate-certainty evidence) and there may be no overall effect when compared to non-absorbable disaccharides (RR 0.97, 95% CI 0.66 to 1.40; P = 85, I2 = 0%; 8 trials, 681 participants; low-certainty evidence). However, there was very low-certainty evidence that use of rifaximin plus a non-absorbable disaccharide may be associated with a lower risk of serious adverse events than use of a non-absorbable disaccharide alone (RR 0.66, 95% CI 0.45 to 0.98; P = 0.04, I2 = 60%; 7 trials, 1076 participants). Rifaximin likely results in an overall effect on health-related quality of life when compared to placebo/no intervention (mean difference (MD) -1.43, 95% CI -2.87 to 0.02; P = 0.05, I2 = 81%; 4 trials, 214 participants; moderate-certainty evidence), and may benefit health-related quality of life in people with minimal hepatic encephalopathy (MD -2.07, 95% CI -2.79 to -1.35; P < 0.001, I2 = 0%; 3 trials, 176 participants). The overall effect on health-related quality of life when comparing rifaximin to non-absorbable disaccharides is very uncertain (MD -0.33, 95% CI -1.65 to 0.98; P = 0.62, I2 = 0%; 2 trials, 249 participants; very low-certainty evidence). None of the combined rifaximin/non-absorbable disaccharide trials reported on this outcome. There is likely an overall beneficial effect on hepatic encephalopathy when comparing rifaximin to placebo/no intervention (RR 0.56, 95% CI 0.42 to 0.77; NNTB = 5; P < 0.001, I2 = 68%; 13 trials, 1009 participants; moderate-certainty evidence). This effect may be more marked in people with minimal hepatic encephalopathy (RR 0.40, 95% CI 0.31 to 0.52; NNTB = 3; P < 0.001, I2 = 10%; 6 trials, 364 participants) and in prevention trials (RR 0.71, 95% CI 0.56 to 0.91; NNTB = 10; P = 0.007, I2 = 36%; 4 trials, 474 participants). There may be little overall effect on hepatic encephalopathy when comparing rifaximin to non-absorbable disaccharides (RR 0.85, 95% CI 0.69 to 1.05; P = 0.13, I2 = 0%; 13 trials, 921 participants; low-certainty evidence). However, there may be an overall beneficial effect on hepatic encephalopathy when comparing rifaximin plus a non-absorbable disaccharide to a non-absorbable disaccharide alone (RR 0.58, 95% CI 0.48 to 0.71; NNTB = 5; P < 0.001, I2 = 62%; 17 trials, 2332 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Compared to placebo/no intervention, rifaximin likely improves health-related quality of life in people with minimal hepatic encephalopathy, and may improve hepatic encephalopathy, particularly in populations with minimal hepatic encephalopathy and when it is used for prevention. Rifaximin likely has no overall effect on mortality, serious adverse events, health-related quality of life, or hepatic encephalopathy compared to non-absorbable disaccharides. However, when used in combination with a non-absorbable disaccharide, it likely reduces overall mortality risk, the risk of serious adverse events, improves hepatic encephalopathy, reduces the length of hospital stay, and prevents the occurrence/recurrence of hepatic encephalopathy. The certainty of evidence for these outcomes is very low to moderate; further high-quality trials are needed.

Assessing Critical Flicker Fusion Frequency: Which Confounders? A Narrative Review

The critical flicker fusion frequency (cFFF) refers to the frequency at which a regularly recurring change of light stimuli is perceived as steady. The cFFF threshold is often assessed in clinics to evaluate the temporal characteristics of the visual system, making it a common test for eye diseases. Additionally, it serves as a helpful diagnostic tool for various neurological and internal diseases. In the field of diving/hyperbaric medicine, cFFF has been utilized to determine alertness and cognitive functions. Changes in the cFFF threshold have been linked to the influence of increased respiratory gas partial pressures, although there exist inconsistent results regarding this effect. Moreover, the use of flicker devices has produced mixed outcomes in previous studies. This narrative review aims to explore confounding factors that may affect the accuracy of cFFF threshold measurements, particularly in open-field studies. We identify five broad categories of such factors, including (1) participant characteristics, (2) optical factors, (3) smoking/drug use, (4) environmental aspects, and (5) breathing gases and partial pressures. We also discuss the application of cFFF measurements in the field of diving and hyperbaric medicine. In addition, we provide recommendations for interpreting changes in the cFFF threshold and how they are reported in research studies.

Prediction and prevention of the first episode of overt hepatic encephalopathy in patients with cirrhosis

Hepatic encephalopathy (HE) is one of the most important complications of patients with liver cirrhosis. In addition, HE is associated with a dismal prognosis and has detrimental effects on patients' quality of life. Thus, it is of pivotal importance to identify patients at high risk for overt HE (OHE) in whom primary prophylaxis may be justified. In this narrative review, we aim to provide insight into predictors and prediction tools for a first-time episode of OHE and to scrutinize the current level of evidence of primary prophylaxis. In recent decades, several cognitive tests, composite scores, and blood-based biomarkers have been demonstrated to be predictive of a first-time episode of OHE. Among the best validated are the established tests for minimal HE, such as the Psychometric Hepatic Encephalopathy Score, determination of the critical flicker frequency, Stroop EncephalApp, or the Animal Naming Test. Individualized risk stratification using blood-based biomarkers and cross-sectional imaging (sarcopenia and spontaneous portosystemic shunts) is coming to the fore, but validation in larger multicenter cohorts is often lacking. On the basis of current evidence, a recommendation for primary prophylaxis of a first episode of OHE cannot be made in general. Only 2 studies have investigated the prevention of a first-time OHE episode as the primary endpoint. In this narrative review, we provide a concise overview of the current evidence levels on prediction tools and pharmacological prevention of a first episode of OHE. In addition, we give an outlook on future research targets to improve knowledge on this important topic.

J-difference GABA-edited MRS reveals altered cerebello-thalamo-cortical metabolism in patients with hepatic encephalopathy

Hepatic encephalopathy (HE) is a common neurological manifestation of liver cirrhosis and is characterized by an increase of ammonia in the brain accompanied by a disrupted neurotransmitter balance, including the GABAergic and glutamatergic systems. The aim of this study is to investigate metabolic abnormalities in the cerebello-thalamo-cortical system of HE patients using GABA-edited MRS and links between metabolite levels, disease severity, critical flicker frequency (CFF), motor performance scores, and blood ammonia levels. GABA-edited MRS was performed in 35 participants (16 controls, 19 HE patients) on a clinical 3 T MRI system. MRS voxels were placed in the right cerebellum, left thalamus, and left motor cortex. Levels of GABA+ and of other metabolites of interest (glutamine, glutamate, myo-inositol, glutathione, total choline, total NAA, and total creatine) were assessed. Group differences in metabolite levels and associations with clinical metrics were tested. GABA+ levels were significantly increased in the cerebellum of patients with HE. GABA+ levels in the motor cortex were significantly decreased in HE patients, and correlated with the CFF (r = 0.73; p < .05) and motor performance scores (r = -0.65; p < .05). Well-established HE-typical metabolite patterns (increased glutamine, decreased myo-inositol and total choline) were confirmed in all three regions and were closely linked to clinical metrics. In summary, our findings provide further evidence for alterations in the GABAergic system in the cerebellum and motor cortex in HE. These changes were accompanied by characteristic patterns of osmolytes and oxidative stress markers in the cerebello-thalamo-cortical system. These metabolic disturbances are a likely contributor to HE motor symptoms in HE. In patients with hepatic encephalopathy, GABA+ levels in the cerebello-thalamo-cortical loop are significantly increased in the cerebellum and significantly decreased in the motor cortex. GABA+ levels in the motor cortex strongly correlate with critical flicker frequency (CFF) and motor performance score (pegboard test tPEG), but not blood ammonia levels (NH3).

Hepatic encephalopathy - recent advances in treatment and diagnosis

INTRODUCTION

Hepatic encephalopathy (HE) is a peculiar kind of brain dysfunction typical of liver cirrhosis characterized by nonspecific neurological and psychiatric manifestations. HE ranges from minimal hepatic encephalopathy (MHE) to the most severe form characterized by alteration of consciousness or coma (overt HE, OHE). Once the diagnosis of OHE is made, every effort to identify and correct the precipitating cause is essential for the resolution of symptoms. Clinical studies that assessed the prevalence and incidence of any type of HE (MHE and OHE) in patients affected by cirrhosis were included in this review. No language, publication date, or publication status restrictions were imposed. The studies were identified by searching electronic databases (PubMed and SCOPUS).

AREAS COVERED

The most widely empirical pharmacological approach consists of non-absorbable antibiotics (rifaximin) and non-absorbable disaccharides (lactulose, lactitol per os and per enemas). Other agents (including branched-chain amino acids, probiotics, other antibiotics, or intravenous L-ornithine L-aspartate) are available, but the evidence supporting their efficacy remains under debate.

EXPERT OPINION

Gray areas and future needs remain the therapeutic approach to MHE and issues in the design of therapeutic studies for HE which have been extensively discussed in this review.

[Hepatic encephalopathy after portosystemic bypass surgery]

The most effective modern treatment for gastrointestinal bleeding following portal hypertension is portosystemic bypass surgery. Hepatic encephalopathy after these procedures is still an urgent problem in modern pediatric surgery, and radical treatment is unknown. To optimize treatment outcomes in children with hepatic encephalopathy, we should choose adequate treatment considering the risk of hepatic encephalopathy in the future. In this review, the authors discuss modern data on hepatic encephalopathy regarding symptoms, advantages and disadvantages of various treatment methods. Risk of hepatic encephalopathy with and without surgical treatment, as well as methods of diagnosis and treatment are particularly analyzed. Total portosystemic bypass surgery, especially portocaval shunt, is followed by higher risk of hepatic encephalopathy compared to selective shunts and physiological mesoportal bypass. The last two approaches are advisable to improve treatment outcomes in children with hepatic encephalopathy.

The effect of induced hyperammonaemia on sleep and melanopsin-mediated pupillary light response in patients with liver cirrhosis: A single-blinded randomized crossover trial

Background & aims

Sleep disturbances are related to hepatic encephalopathy and hyperammonaemia in patients with cirrhosis. The circadian rhythm is regulated by light stimulation of the retina via melanopsin-containing ganglion cells. The study aimed to investigate whether induced hyperammonaemia affects the pupillary light response and sleep efficiency in patients with cirrhosis.

Methods

The study was a single-blinded crossover trial including nine patients with cirrhosis. Sleep was evaluated by Pittsburgh Sleep Quality Index (PSQI) and monitored for twelve nights with wrist accelerometers and sleep diaries. On two experimental days, separated by one week, patients were randomized to ingest either an oral amino acid challenge (AAC) or an isocaloric glucose solution (GS). We measured pupillary light response, capillary ammonia, the Karolinska Sleepiness Scale (KSS), and two neuropsychological tests on both experimental days.

Results

The patients had poor self-assessed sleep quality. The amino acid challenge led to a significant increase in capillary ammonia and KSS. The time spent in bed sleeping after AAC was longer and with a reduced movement index compared to baseline but not different from GS. We found no difference in the pupillary light response or neuropsychiatric tests when comparing the effect of AAC with GS.

Conclusions

Patients with cirrhosis had impaired sleep quality. Induced hyperammonaemia led to increased sleepiness but had no acute effect on pupillary light response or the neuropsychiatric tests.

Trial registration

Registration number: NCT04771104.

Hepatic encephalopathy

Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.

Digital Eyestrain and the Critical Fusion Frequency

SIGNIFICANCE

Although the high prevalence of digital eyestrain has been well established, to date, there is no objective measurement of this condition. Previous studies have suggested that digital eyestrain may be associated with decreased critical fusion frequency, but the published evidence to support this association is sparse.

PURPOSE

This study sought to determine whether symptoms of digital eyestrain after a sustained computer task are indeed associated with changes in critical fusion frequency.

METHODS

The experiment was performed on 30 young visual-normal subjects. They attended two sessions, during which they undertook a 20-minute reading task. This comprised either reading random words from a tablet computer or a story from a printed children's book. Critical fusion frequency was measured both before and immediately after each of the reading tasks. In addition, the level of digital eyestrain was assessed by subjects completing a questionnaire regarding ocular and visual symptoms experienced during each of the reading trials.

RESULTS

The mean increase in digital eyestrain symptoms after the digital and printed conditions was 11.37 (standard error of the mean [SEM], 2.23) and 4.40 (SEM, 1.34), respectively. Both the post-task symptom change (P < .001) and the difference between the two reading conditions (P = .004) were significant. The mean change in critical fusion frequency after the digital and printed conditions was -0.42 (SEM, 0.25) and -0.72 (SEM, 0.26), respectively. Neither the post-task change nor the difference between the two reading conditions was significant. In addition, when considering the digital condition only, no significant correlation was observed between the changes in critical fusion frequency and reported symptoms.

CONCLUSIONS

These results do not support the proposal that changes in critical fusion frequency can be used as an objective measure of eyestrain or other symptoms of digital eyestrain.

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?

Minimal hepatic encephalopathy - diagnosis and treatment

Hepatic encephalopathy is a dysfunction of the central nervous system caused by chronic and acute liver disease. It presents a wide spectrum of symptoms from undetectable in a standard clinical examination to hepatic coma. The mildest form of hepatic encephalopathy is minimal hepatic encephalopathy. It significantly influences the quality of life, prognosis, and the incidence of complications. A wide range of psychometric and neurophysiological tests are used in the diagnostics. Treatment is based on the same principles as in overt encephalopathy. The most commonly used drugs include rifaximin, ornithine aspartate, and LOLA.

Antibiotics and Liver Cirrhosis: What the Physicians Need to Know

The liver is the primary site of drug metabolism, which can be altered by a variety of diseases affecting the liver parenchyma, especially in patients with liver cirrhosis. The use of antibiotics in patients with cirrhosis is usually a matter of concern for physicians, given the lack of practical knowledge for drug choice and eventual dose adjustments in several clinical scenarios. The aim of the current narrative review is to report, as broadly as possible, basic, and practical knowledge that any physician should have when approaching a patient with liver cirrhosis and an ongoing infection to efficiently choose the best antibiotic therapy.

Determination of Turkish norms of psychometric tests for diagnosing minimal hepatic encephalopathy and proposal of a high sensitive screening test battery

BACKGROUND

Psychometric hepatic encephalopathy score (PHES) needs local standardization.

AIMS

This study aimed at standardizing PHES for Turkish patients and compare them with German norms; to determine minimal hepatic encephalopathy (mHE) prevalence with two different methods [PHES battery and Critical Flicker Frequency (CFF)] and to assess whether sub-tests of the battery can be used for screening for mHE.

METHODS

Healthy volunteers (n = 816; 400 male) and cirrhotics (n = 124; 58 male) were included. For mHE diagnosis PHES score threshold was set at ≤ - 5 points and that of CFF at < 39 Hz. For comparing German and Turkish norms, datasets were combined. Multiple backward procedure was applied to assess effects of age, sex and education on single tests of the battery. Receiver operating characteristic (ROC) curves were created for assessing diagnostic capabilities of subtests of the battery.

RESULTS

PHES norms for Turks were developed. MHE prevalence in compensated cirrhotics was 29.8% and 27.4% with PHES and CFF tests, respectively, with low compatibility (kappa coefficient 0.389); mHE prevalence decreased to 16% when both tests were combined. Turks performed worse vs Germans in the digit symbol (DS) and serial dotting (SD) subtests but performed better in other subtests. In ROC analyzes of subtests, the combination of DS + SD tests achieved an AUROC of 0.974 versus PHES.

CONCLUSIONS

Use of two methods for diagnosing mHE is important for research purposes. From a clinical perspective, sensitivity with acceptable specificity may suffice for screening instruments for mHE. Combined use of DS and SD subtests of the PHES battery appears suitable for this purpose.

Evaluation of different diagnostic modalities of minimal hepatic encephalopathy in cirrhotic patients: case-control study

Introduction

Minimal hepatic encephalopathy (MHE) represents one of the most overlooked complications of liver cirrhosis.

Aim of the study

To compare the utility and efficacy of different MHE diagnostic modalities.

Material and methods

This case-control study was conducted on hepatitis C virus (HCV)-related compensated cirrhotic patients. The Psychometric Hepatic Encephalopathy Score (PHES) was used to assign patients to MHE and controls. All patients were subjected to plasma ammonia, serum 3-nitrotyrosine (3-NT), critical flicker frequency (CFF), and the modified inhibitory control test (ICT).

Results

CFF was significantly lower in the control group (38.5, 40 Hz, p = 0.003). The unweighted lures on ICT were 8.7, 4.9 in MHE and controls (p < 0.001). Moreover, ammonia was higher in the MHE group (89, 61.5 µmol/l, p < 0.001). 3-NT was also higher in the MHE group (31.5, 13.7 nmol/l, p < 0.001) respectively. CFF at cutoff < 39 Hz had sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 57.5%, 77.5%, 71.9% and 64.6%, respectively; in modified ICT, at cutoff > 5 unweighted lures the values were 87.5%, 80%, 81.4% and 86.5%, respectively; in ammonia, at cutoff ≥ 76.45 µmol/l the values were 65%, 72.5%, 70.3% and 67.4%, respectively; for 3-NT at cutoff ≥ 14.15 nmol/l the values were 85%, 82.5%, 82.9% and 84.6%, respectively. The accuracy for MHE diagnosis was 67.5%, 83.3%, 68.8%, 83.8% relying on CFF, 3-NT, ammonia, and ICT respectively. On multivariate analysis, CFF < 39 Hz (OR = 10.2, p = 0.04), modified ICT > 5 unweighted lures (OR = 43.2, p = 0.002), and serum 3-NT levels ≥ 14.15 nmol/l (OR = 50.4, p < 0.001) were independent predictors of MHE.

Conclusions

3-NT and ICT are advantageous to reveal MHE in compensated liver cirrhosis, while CFF can be only used as adjuncts, with humble merits of ammonia.

Artificial Intelligence and Its Application to Minimal Hepatic Encephalopathy Diagnosis

Hepatic encephalopathy (HE) is a brain dysfunction caused by liver insufficiency and/or portosystemic shunting. HE manifests as a spectrum of neurological or psychiatric abnormalities. Diagnosis of overt HE (OHE) is based on the typical clinical manifestation, but covert HE (CHE) has only very subtle clinical signs and minimal HE (MHE) is detected only by specialized time-consuming psychometric tests, for which there is still no universally accepted gold standard. Significant progress has been made in artificial intelligence and its application to medicine. In this review, we introduce how artificial intelligence has been used to diagnose minimal hepatic encephalopathy thus far, and we discuss its further potential in analyzing speech and handwriting data, which are probably the most accessible data for evaluating the cognitive state of the patient.

Standardization of the psychometric hepatic encephalopathy score in a French population

The Psychometric Hepatic Encephalopathy Score (PHES) has previously been standardized in thirteen countries on three continents, confirming its status of gold standard test to detect minimal hepatic encephalopathy (MHE). In the meantime, performance has also been shown to vary with variables such as age, education, and barely sex. The present study aimed at standardizing the PHES in a French population. One hundred and ninety-six French healthy participants completed a French version of the paper-and-pencil PHES, involving five tests and six measures. Importantly, the balance was perfect between all levels of the three controlled factors, which were sex, age (seven decade-levels from 20–29 to 80–89 years), and education (two levels below or above 12 years of education). Raw measures were transformed to fit the normal distribution. ANOVAs on transformed variables showed no effect of sex, but an effect of age on all measures, and of education on five measures. Multiple or simple regressions were completed to build up normograms. Thorough analysis of variability within each test failed to find outliers that may bias the results. Comparison between French and seminal German data showed that they highly fitted though cultural and cognitive style specificities could be observed. This is the first study to standardize the PHES in a French population and to extensively explore the effects of sex, age and education using perfectly balanced samples. Subtle differences between countries of the same continent emphasize the need to build up normative data in each country to get accurate PHES in patients.

Risk of recurrent hepatic encephalopathy in patients with liver cirrhosis: a German registry study

BACKGROUND AND AIMS

Patients with hepatic encephalopathy (HE) show low quality of life, recurrent hospitalizations and an increased mortality. We aimed to assess the natural course of patients after a recent episode of overt HE and to identify risk factors for HE recurrence in Germany.

METHODS

Fifteen sites took part in a prospective, observational study including patients with liver cirrhosis who had been hospitalized for HE within 3 months before recruitment. Clinical data, psychometric hepatic encephalopathy score (PHES) and critical flicker frequency were assessed quarterly for 1 year. Primary endpoint was HE recurrence requiring hospitalization, all-cause-mortality was treated as a competing risk factor.

RESULTS

From January 2014 to March 2016, a total of 115 patients were recruited. Overall 14 premature deaths were documented. For 78 subjects follow-up data were available in accordance with the protocol. After a median of 118 days, more than half of the per-protocol cohort was readmitted to hospital due to HE (N = 34) or died (N = 11). The risk for hospitalization was significantly increased in patients who had been recruited by liver transplant centers (P = 0.003), had had frequent HE relapses prior to recruitment (P = <0.0001) or an abnormal PHES result of <-4 (P = 0.044). Abnormal PHES results barely missed level of significance as an independent risk factor for re-hospitalization in a multivariable competing risk model (P = 0.093).

CONCLUSION

Patients with a history of HE are at high risk for the development of recurrent overt HE demanding hospitalization. The PHES test may aid in detection, monitoring and risk stratification of recurrent HE.

Altered motor cortical plasticity in patients with hepatic encephalopathy: A paired associative stimulation study

OBJECTIVE

Hepatic encephalopathy (HE) is a potentially reversible brain dysfunction caused by liver failure. Altered synaptic plasticity is supposed to play a major role in the pathophysiology of HE. Here, we used paired associative stimulation with an inter-stimulus interval of 25 ms (PAS25), a transcranial magnetic stimulation (TMS) protocol, to test synaptic plasticity of the motor cortex in patients with manifest HE.

METHODS

23 HE-patients and 23 healthy controls were enrolled in the study. Motor evoked potential (MEP) amplitudes were assessed as measure for cortical excitability. Time courses of MEP amplitude changes after the PAS25 intervention were compared between both groups.

RESULTS

MEP-amplitudes increased after PAS25 in the control group, indicating PAS25-induced synaptic plasticity in healthy controls, as expected. In contrast, MEP-amplitudes within the HE group did not change and were lower than in the control group, indicating no induction of plasticity.

CONCLUSIONS

Our study revealed reduced synaptic plasticity of the primary motor cortex in HE.

SIGNIFICANCE

Reduced synaptic plasticity in HE provides a link between pathological changes on the molecular level and early clinical symptoms of the disease. This decrease may be caused by disturbances in the glutamatergic neurotransmission due to the known hyperammonemia in HE patients.

Pathomechanisms in hepatic encephalopathy

Hepatic encephalopathy (HE) is a frequent neuropsychiatric complication in patients with acute or chronic liver failure. Symptoms of HE in particular include disturbances of sensory and motor functions and cognition. HE is triggered by heterogeneous factors such as ammonia being a main toxin, benzodiazepines, proinflammatory cytokines and hyponatremia. HE in patients with liver cirrhosis is triggered by a low-grade cerebral edema and cerebral oxidative/nitrosative stress which bring about a number of functionally relevant alterations including posttranslational protein modifications, oxidation of RNA, gene expression changes and senescence. These alterations are suggested to impair astrocyte/neuronal functions and communication. On the system level, a global slowing of oscillatory brain activity and networks can be observed paralleling behavioral perceptual and motor impairments. Moreover, these changes are related to increased cerebral ammonia, alterations in neurometabolite and neurotransmitter concentrations and cortical excitability in HE patients.

Therapeutic Applications of Resveratrol in Hepatic Encephalopathy through Its Regulation of the Microbiota, Brain Edema, and Inflammation

Hepatic encephalopathy is a common complication in patients with liver cirrhosis and portosystemic shunting. Patients with hepatic encephalopathy present a variety of clinical features, including neuropsychiatric manifestations, cognitive dysfunction, impaired gut barrier function, hyperammonemia, and chronic neuroinflammation. These pathogeneses have been linked to various factors, including ammonia-induced oxidative stress, neuronal cell death, alterations in the gut microbiome, astrocyte swelling, and blood-brain barrier disruptions. Many researchers have focused on identifying novel therapeutics and prebiotics in the hope of improving the treatment of these conditions. Resveratrol is a natural polyphenic compound and is known to exert several pharmacological effects, including antioxidant, anti-inflammatory, and neuroprotective activities. Recent studies suggest that resveratrol contributes to improving the neuropathogenic effects of liver failure. Here, we review the current evidence describing resveratrol's effects in neuropathogenesis and its impact on the gut-liver axis relating to hepatic encephalopathy. We highlight the hypothesis that resveratrol exerts diverse effects in hepatic encephalopathy and suggest that these effects are likely mediated by changes to the gut microbiota, brain edema, and neuroinflammation.

Minimal portosystemic encephalopathy: A new nosological entity in patients with hereditary haemorrhagic telangiectasia

BACKGROUND

Portosystemic shunts in Hereditary Haemorrhagic Telangiectasia (HHT) are often overlooked by conventional imaging although they could reduce hepatic clearance of gut-derived toxins.

AIMS

To evaluate, the presence of subclinical neurological alterations (SNAs), that we named "minimal portosystemic encephalopathy" (mPSE) in HHT patients without advanced liver disease (ALD).

METHODS

In this cross sectional study, consecutive HHT outpatients were firstly screened by critical flicker frequency (CFF) test (abnormal ≤39Hz), and the simplified animal naming test (S-ANT₁) (abnormal <15) was used to confirm the diagnosis of mPSE. Furthermore, we evaluated the effect of lactulose administration on mPSE. Multi-slice CT, cerebral dynamic magnetic resonance, laboratory analyses and transient elastography were also used.

RESULTS

None of the 37 enrolled patients showed portosystemic shunts at imaging techniques. However, 33 patients had normal CFF values (CFF-) and 4 displayed CFF alterations (37.0±0.7Hz, CFF+). The S-ANT₁ confirmed an impaired neurological performance (10.2±2.8) in CFF+ patients thus confirming the presence of mPSE. Noteworthy, lactulose administration determined a CFF increase (39.1±0.4Hz) and S-ANT₁ normalization in these patients. Neither mPSE- nor mPSE+ patients had ALD and showed similar demographic, clinical and laboratory parameters. Finally, no mPSE+ patient showed radiologically-detectable brain vascular malformations or other brain abnormalities at imaging.

CONCLUSIONS

HHT patients represent a human model of mPSE secondary to portosystemic shunts escaping radiological detection. mPSE evaluation should be incorporated in HHT surveillance protocols since it can affect both health-related/social aspects and pharmacokinetics of orally administered drugs with a narrow therapeutic index and high hepatic first-pass uptake.

Hepatitis C related cognitive impairment: Impact of viral and host factors and response to therapy

Chronic hepatitis C virus (HCV) infection is associated with cognitive impairment via several suggested mechanisms including direct neurotoxicity and minimal hepatic encephalopathy. The prevalence of HCV-related cognitive impairment and whether it is reversed by anti-viral therapy is unknown. We aimed to assess predictors and reversibility of cognitive impairment of HCV-infected patients after successful treatment. Consecutive HCV patients treated during the EMERALD study (AbbVie 3D regimen for protease inhibitors failure) underwent neuropsychological (number connection test A [NCTA] and digital symbol test [DST]) and neurophysiological (critical flicker frequency [CFF]) tests at baseline and at 12 weeks post-treatment. Patient self-reported outcomes (PROs) were prospectively collected. Patients with a history of hepatic encephalopathy were excluded. Thirty-two patients underwent the cognitive tests at baseline. Seven of them had abnormal CFF test findings. Twenty-five (25/32, 78%) patients had repeated evaluations 3 months post-treatment. High viral loads were significantly associated with abnormal CFF across fibrosis levels (area under the ROC curve 0.817). CFF results significantly improved following viral eradication, from 40.9 (interquartile range 38.6-42.9) at baseline to 41.5 (39.8-44), p = .042, at follow-up. Both NCTA and DST results improved, but not significantly. There was improvement in the PROs of general health perception and vitality. The NCTA and DST results were more significantly associated with PROs than CFF. This prospective interventional study showed greater cognitive impairment in HCV patients with high viral load and demonstrated partial reversibility of HCV neurotoxicity and subsequent improvement in PROs following treatment.

Development and Validation of a Clinical-Genetic Risk Score to Predict Hepatic Encephalopathy in Patients With Liver Cirrhosis

INTRODUCTION

We aimed to define the impact of the genetic background on overt hepatic encephalopathy (HE) in patients with liver cirrhosis by developing a combined clinical-genetic risk score.

METHODS

Patients suffering from liver cirrhosis from the outpatient clinics of 4 hospitals (n = 600) were included and followed up for at least 5 years until HE bouts, liver transplant, or death. Patients were genotyped for 60 candidate single nucleotide polymorphisms together with the microsatellite in the promoter region of the gene GLS.

RESULTS

Single nucleotide polymorphisms rs601338 (FUT2), rs5743836 (TRL9), rs2562582 (SLC1A3), rs313853 (SLC1A5), and GLS microsatellite did predict independently the incidence and severity of overt HE and were included as genetic score. Competing risk analysis revealed that bilirubin (subhazard ratio [sHR] 1.30 [1.15-1.48], P < 0.001), albumin (sHR 0.90 [0.86-0.93], P < 0.001), genetic score (sHR 1.90 [1.57-2.30], P < 0.001), and previous episodes of overt HE (sHR 2.60 [1.57-4.29], P < 0.001) were independently associated to HE bouts during the follow-up with an internal (C-index 0.83) and external validation (C-index 0.74). Patients in the low-risk group had 5% and 12% risk of HE at 1 (log-rank 92.1; P < 0.001) and 5 (log-rank 124.1; P < 0.001) years, respectively, whereas 36% and 48% in the high-risk group.

DISCUSSION

The genetic background influenced overt HE risk and severity. The clinical-genetic HE Risk score, which combined genetic background together with albumin, bilirubin, and previous episodes of overt HE, could be a useful tool to predict overt HE in patients with cirrhosis.

Outcome Prediction of Covert Hepatic Encephalopathy in Liver Cirrhosis: Comparison of Four Testing Strategies

Despite the negative impact of covert hepatic encephalopathy on the outcome of patients with liver cirrhosis, data regarding the ability of different testing strategies to predict overt hepatic encephalopathy (OHE) development and mortality are limited. This study aimed to compare the ability of Psychometric Hepatic Encephalopathy Score (PHES), critical flicker frequency (CFF), simplified animal naming test (S-ANT1), and clinical covert hepatic encephalopathy (CCHE) score to predict OHE development and mortality.

Diagnosis and Management of Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a severe complication of cirrhosis. The prevalence of overt HE (OHE) ranges from 30% to 45%, whereas the prevalence of minimal HE (MHE) is as high as 85% in some case series. Widespread use of transjugular intrahepatic portosystemic shunt to control complications related to portal hypertension is associated with an increase in HE incidence. If the diagnosis of OHE remains simple in most cases, then the diagnosis of MHE is less codified because of many differential diagnoses with different therapeutic implications. This review analyzes current knowledge about the pathophysiology, diagnosis, and different therapeutic options of HE.

A novel method: can stapedial acoustic reflex have a role in the diagnosis of minimal hepatic encephalopathy?

OBJECTIVE

Stapedial acoustic reflex is an easily accessible and applicable test which is also valuable for the clinical conditions which affect the various locations of the central nervous system. Searching the diagnostic value of stapedial acoustic reflex at minimal hepatic encephalopathy is the aim of this research.

METHODS

Diagnosis of minimal hepatic encephalopathy was conducted by mini-mental state and critical flickered frequency tests. Minimal hepatic encephalopathy diagnosed patients were established in the first group. Cirrhosis (without minimal hepatic encephalopathy or overt hepatic encephalopathy) diagnosed patients were created the control group. The stapedial acoustic reflex test was applied for minimal hepatic encephalopathy and the control group by audiologists in a soundproof room.

RESULTS

In total, 221 patients were screened and 97 patients meet the inclusion criterions. Out of 97 patients, 52 were the minimal hepatic encephalopathy patients and the remaining patients were the control group. Acoustic reflex tests battery includes the evaluation of two pathways called ipsilateral and contralateral. Ipsilateral way test results were found positive in all minimal hepatic encephalopathy patients and 95% positive in the control group. Contralateral acoustic reflex test results were found 36% positive in minimal hepatic encephalopathy patients and 95% positive in the control group, respectively. A comparison of ipsilateral and contralateral acoustic reflex test results was displayed a statistical significance.

CONCLUSION

Stapedial acoustic reflex test results of cirrhosis patients may cover additional parameters for the diagnosis of minimal hepatic encephalopathy.

Undersampled Differential Phase Shift On–Off Keying for Visible Light Vehicle-to-Vehicle Communication

An important development direction for the future of the automotive industry is connected and cooperative vehicles. Some functionalities in traffic need the cars to communicate with each other. In platooning, multiple cars driving in succession reduce the distances between them to drive in the slipstream of each other to reduce drag, energy consumption, emissions, and the probability of traffic jams. The car in front controls the car behind remotely, so all cars in the platoon can accelerate and decelerate simultaneously. In this paper, a system for vehicle-to-vehicle communication is proposed using modulated taillights for transmission and an off-the-shelf camera with CMOS image sensor for reception. An Undersampled Differential Phase Shift On–Off Keying modulation method is used to transmit data. With a frame sampling rate of 30 FPS and two individually modulated taillights, a raw data transmission rate of up to 60 bits per second is possible. Of course, such a slow communication channel is not applicable for time-sensitive data transmission. However, the big benefit of this system is that the identity of the sender of the message can be verified, because it is visible in the captured camera image. Thus, this channel can be used to establish a secure and fast connection in another channel, e.g., via 5G or 802.11p, by sending a verification key or the fingerprint of a public key. The focus of this paper is to optimize the raw data transmission of the proposed system, to make it applicable in traffic and to reduce the bit error rate. An improved modulation mode with smoother phase shifts is used that can reduce the visible flickering when data is transmitted. By additionally adjusting the pulse width ratio of the modulation signal and by analyzing the impact of synchronization offsets between transmitter and receiver, major improvements of the bit error rate (BER) are possible. In previously published research, such a system without the mentioned adjustments was able to transmit data with a BER of 3.46%. Experiments showed that with those adjustments a BER of 0.48% can be achieved, which means 86% of the bit errors are prevented.

Brain-derived neurotrophic factor as a potential diagnostic marker in minimal hepatic encephalopathy

Introduction

Minimal hepatic encephalopathy (MHE) is a common complication of liver cirrhosis not only leading to a decrease in the quality of life, but also predicting development of overt encephalopathy. The diagnosis of MHE usually relies on a combination of neuropsychological tests, while robust serum biomarkers are lacking. We aimed to assess serum concentrations of brain-derived neurotrophic factor (BDNF) in MHE patients.

Material and methods

Serum BDNF was assessed in 78 patients with liver cirrhosis (53 male, median age 55 years) and 40 healthy individuals. 43 subjects underwent extensive evaluation for MHE by psychometric hepatic encephalopathy score (PHES) and inhibitory control test (ICT) or critical flicker frequency (CFF).

Results

Serum BDNF was twofold lower in liver cirrhosis compared to healthy subjects [13.6 (7.8-22.6) vs. 33.0 (24.1-40.7) ng/ml, p < 0.001] and its decrease reflected a degree of liver insufficiency assessed by model for end-stage liver disease (MELD). BDNF showed a negative correlation with bilirubin (R = –0.35, p = 0.005) and international normalized ratio (INR) (R = –0.37, p = 0.003), and positive with platelets (PLT) (R = 0.36, p = 0.004), while no associations with age, sex, body mass index (BMI), waist-hip ratio (WHR), creatinine and ammonia were noted. Importantly, subjects with a diagnosis of MHE by at least two modalities showed the lowest levels of BDNF [10.9 (2.5-14.4) vs. 19.9 (9.3-29.4) ng/ml, p < 0.01]. Patients with self-reported sleep disturbances had significantly lower serum BDNF [13.0 (2.5-23.4) vs. 20.0 (8.4-31.3) ng/ml, p = 0.04].

Conclusions

The lowest serum BDNF concentration was noted in patients with MHE and sleep disturbances, which suggests a role in pathophysiology of hepatic encephalopathy but also as a potential biomarker.

Hepatic Encephalopathy: Diagnosis and Management

Type C hepatic encephalopathy (HE) is a brain dysfunction caused by severe hepatocellular failure or presence of portal-systemic shunts in patients with liver cirrhosis. In its subclinical form, called “minimal hepatic encephalopathy (MHE), only psychometric tests or electrophysiological evaluation can reveal alterations in attention, working memory, psychomotor speed and visuospatial ability, while clinical neurological signs are lacking. The term “covert” (CHE) has been recently used to unify MHE and Grade I HE in order to refer to a condition that is not unapparent but also non overt. “Overt” HE (OHE) is characterized by personality changes, progressive disorientation in time and space, acute confusional state, stupor and coma. Based on its time course, OHE can be divided in Episodic, Recurrent or Persistent. Episodic HE is generally triggered by one or more precipitant factors that should be found and treated. Unlike MHE, clinical examination and clinical decision are crucial for OHE diagnosis and West Haven criteria are widely used to assess the severity of neurological dysfunction. Primary prophylaxis of OHE is indicated only in the patient with gastrointestinal bleeding using non-absorbable antibiotics (Rifaximin) or non-absorbable disaccharides (Lactulose). Treatment of OHE is based on the identification and correction of precipitating factors and starting empirical ammonia-lowering treatment with Rifaximin and Lactulose (per os and enemas). The latter should be used for secondary prophylaxis, adding Rifaximin if HE becomes recurrent. In recurrent/persistent HE, the treatment options include fecal transplantation, TIPS revision and closure of eventual splenorenal shunts. Treatment of MHE should be individualized on a case-by-case basis.

Covert hepatic encephalopathy and spontaneous portosystemic shunts increase the risk of developing overt hepatic encephalopathy

AIM

The aim of the study was to evaluate the presence of covert hepatic encephalopathy (cHE) and its characteristics according to the presence of spontaneous portosystemic shunts (SPSS) and their influence on the development of overt hepatic encephalopathy.

METHODS

Secondary analysis of a multicentre study, which evaluated the association between SPSS and complications of cirrhosis. The present study population includes those patients who also underwent cHE diagnostic evaluation. Presence of SPSS was evaluated by cross-sectional imaging and quantified by total SPSS-area. Logistic and Cox-regression competing risk analyses were performed.

RESULTS

About 65 patients were included of age 58 (IQR 50-66), MELD 15 (IQR 10-20), with alcoholic liver disease 63%. Thirty-two patients (49%) had cHE, had higher MELD [16 (IQR 12-24) vs 13 (IQR 9-17), P = .027], a greater proportion of SPSS [n = 18 (56%) vs n = 8 (24%); P = .008] and a higher total cross-sectional SPSS-area [28.3 (0-94.2) vs 0 (0-14.1); P = .005]. On multivariate analysis MELD [OR 1.11 (95% CI 1.01-1.21)] and presence of SPSS [OR 3.95 (95% CI 1.22-12.80)] were independently associated to cHE at baseline. During follow-up cHE was an independent predictor of oHE [cHE: HR 6.93 (95% CI 2.64-18.20). The effect of cHE on the development of oHE was greater in patients with SPSS [only cHE: HR 5.66 (95% CI 1.82-17.62), cHE and SPSS: HR 8.63 (95% CI 3.15-23.65)].

CONCLUSIONS

cHE is independently associated to the presence of SPSS (and total cross-sectional SPSS-area) and MELD. Furthermore, the presence of SPSS seems to increase the risk of cHE of developing of overt hepatic encephalopathy.

Sleep disorder in patients with chronic liver disease: a narrative review

Sleep disturbance is a common feature of chronic liver disease (CLD) with impact on health-related quality of life; 60-80% of patients with CLD report subjective poor sleep; frequent presentations of sleep disturbance include insomnia, reduced sleep efficiency, increased sleep latency, reduced time in rapid eye movement (REM) sleep, restless leg syndrome and excessive daytime sleepiness (EDS). Key contributors to sleep disturbance include hepatic encephalopathy (HE) and circadian rhythm imbalance due to altered melatonin metabolism. Specific conditions causing CLD, such as non-alcoholic fatty liver disease (NAFLD), chronic viral hepatitis and primary biliary cholangitis (PBC) result in different types of sleep disturbance, and the treatment of these conditions can often also lead to sleep disturbance. There are currently limited management options for sleep disturbance in CLD. Obstructive sleep apnoea (OSA) is a common condition that causes chronic intermittent hypoxia due to airway collapse during sleep. This chronic intermittent hypoxia appears to contribute to the development of NAFLD. The presence of reactive oxygen species and the overexpression of hypoxia inducible factor 1-alpha secondary to hypoxia may be responsible for the second 'hit' of the 'two-hit' hypothesis of NAFLD. Treatment of the intermittent hypoxia with continuous positive airway pressure therapy has limited efficacy against liver dysfunction. There remain many outstanding areas of investigation in the management of sleep disturbance in CLD, and of liver dysfunction in OSA.

A dichoptic presentation device and a method for measuring binocular temporal function in the visual system

Recent studies highlight the importance of the temporal domain in visual processing. Critical Flicker Frequency (CFF), the frequency at which a flickering light is perceived as continuous, is a widely used measure for evaluating visual temporal processing. Another important issue to investigate is the cortical interactions arising between the flicker stimuli of both eyes. This paper presents a robust and reliable dichoptic tool for evaluating the CFF threshold in both eyes. This system is based on an analog output device used to independently drive two LEDs through a custom-written MATLAB code (using a laptop PC) for eliciting sinusoidal flickering stimuli and for psychophysically measuring the perceived CFF threshold. The luminance and phases of each LED are individually controlled, enabling the investigation of the effect of phase and luminance differences on binocular summation in subjects with different ocular pathologies. Experiments were designed to evaluate the CFF threshold through a psychophysical test, based on a discrimination task with a stimulus duration of 1 s, based on a temporal alternative forced-choice paradigm. The target stimulus temporal features were modulated using the staircase method. Subjects were requested to discriminate between a target stimulus (a flickering light at various frequencies) and a flickering light at a frequency of 120 Hz, which is significantly higher than the CFF in humans; therefore, it is perceived as constant. One of the main advantages of the introduced dichoptic presentation system is that it enables the visual temporal performance to be measured under both monocular and binocular conditions where phenomena such as temporal binocular summation (BS) can be evaluated. Moreover, the system offers great flexibility by introducing a stimulus phase shift, which enables studying how stimulus timing affects the temporal function at millisecond scale resolution. Our results confirm that no crosstalk exists between the eyes and that the system can reliably separate the stimuli presented to the eyes. Using this set-up, we observed the binocular summation of CFF for low target luminance levels. The CFF was significantly (p = 0.011) higher (5.2%) under binocular compared with monocular viewing conditions. More importantly, introducing an inter - ocular phase shift reduced the binocular CFF in normally sighted subjects. Finally, in amblyopic subjects the amblyopic eye showed a decrease of 3.9 Hz (15%) in CFF, compared with the fellow eye (p = 0.001). The ability to assess binocular temporal performance using a dichoptic display can shed light on visual temporal performance in general, and on binocular temporal summation processes in particular, both for subjects with normal binocular vision and for subjects with impaired binocular vision (e.g., amblyopic subjects). Furthermore, such a presentation set-up may facilitate the development of training paradigms aimed at improving binocular vision performance. In this paper we describe the system and methods in detail and provide all necessary computer code and other details that will enable an easy and quick adaptation of the method by scientists interested in studying the temporal resolution of the visual system in general, and in studying inter-ocular differences or interactions in particular.

Novel computerized psychometric tests as primary screening tools for the diagnosis of minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) is a critical neurocognitive complication of decompensated liver cirrhosis and portosystemic shunting, which results in a wide range of cognitive deficits including impairments in working attention, psychomotor speed, and executive function. Current guidelines have recommended paper-and-pencil psychometric tests for the diagnosis of MHE. Most high-risk cirrhotic patients are required to be examined; however, paper-and-pencil psychometric tests are neither convenient nor rapid to perform in the clinic. Recently, novel computerized psychometric tests, including the inhibitory control test, EncephalApp Stroop App, and critical flicker frequency, have been proven to be rapid, effective, and convenient methods for screening MHE in clinical practice and for identifying high-risk cirrhotic patients for further validation using rigid neuropsychometric examinations. However, diagnostic accuracy of these tests is influenced by educational background, age, and cultural differences. This review summarizes clinical evidence of the application of novel computerized psychometric tests for screening MHE.

Impaired brain function improved by L-carnitine in patients with cirrhosis: evaluation using near-infrared spectroscopy

To evaluate the effects of l-carnitine on impaired brain function in patients with liver cirrhosis. We conducted a retrospective cohort study that included sequential 80 liver cirrhosis patients with impaired brain function evaluated using near-infrared spectroscopy (NIRS). Among them, l-carnitine was administered to 48 patients. The NIRS data and blood ammonia level at baseline and after 8 weeks of treatment were compared between patients administered with l-carnitine (l-carnitine group) and those who were not (control group). The NIRS data at baseline were similar between the l-carnitine and control groups (0.04 ± 0.04 vs. 0.04 ± 0.05 mMmm, p = n.s), whereas those in the l-carnitine group (n = 48) were significantly better than that of the control group at 8 weeks of treatment (n = 32) (0.103 ± 0.081 vs. 0.040 ± 0.048 mMmm, p < 0.001). In the l-carnitine group, 35.4% (17/48) of patients had hyperammonemia. The NIRS data of the l-carnitine group at 8 weeks of treatment were significantly improved than that of the control group, irrespective of baseline ammonia levels (0.11 ± 0.09 vs. 0.04 ± 0.05 mMmm, p = 0.005, and 0.10 ± 0.06 vs. 0.02 ± 0.03 mMmm, p = 0.003, for normal baseline ammonia and elevated ammonia levels, respectively). In the multivariate analysis, l-carnitine administration (odds ratio [OR] 3.51, 95% confidence interval [CI] 1.23–9.99, p = 0.019) and baseline NIRS data of ≤ 0.07 mMmm (OR 5.21, 95% CI 1.69–16.0, p = 0.0041) were found as independent significant factors. l-carnitine improves impaired brain function in patients with liver cirrhosis.

Impact of sustained viral response in the evolution of minimal hepatic encephalopathy: A prospective pilot study

INTRODUCTION AND AIMS

To determine the prevalence of minimal hepatic encephalopathy(MHE) in patients with liver cirrhosis (LC) due to hepatitis C virus (HCV) infection and to evaluate the impact of sustained viral response (SVR) on MHE.

MATERIALS AND METHODS

We performed a prospective study using MHE screening and follow-up on patients with HCV and LC. The patients were evaluated at the beginning of treatment and 24 weeks after treatment.

RESULTS

64 patients were included. 51.6% were male, the median age was 62 years, Child-Pugh classification A/B/C 93.8%/4.7%/1.6% and median MELD was 8.3. Prior hydropic decompensation was present in 11 patients. Median values of liver stiffness, as measured by transient elastography (TE) were 22.8kPa. Indirect signs of portal hypertension (PH) were present in 53.1% of patients, with a mean of 11.9mmHg among the ones with a measurement of the hepatic venous pressure gradient. The prevalence of MHE before treatment was 26.6%. After treatment, 98.4% of patients achieved SVR. The presence of MHE at 24 weeks post-treatment had an statistically significant association with the presence of pre-treatment MHE (80% vs. 21.6%; p<0.01), higher MELD scores at 24-weeks post-treatment (9.8 vs. 8; p=0.02), higher Child-Pugh scores at 24-weeks post-treatment (p=0.04), higher baseline INR levels (1.4 vs. 1.1; p<0.001) and with the presence of indirect signs of PH (100% vs. 47.1%; p=0.02). During follow-up, those patients without MHE at 24 weeks post-treatment had a higher probability of experiencing an improvement in post-treatment TE (80.9% vs. 40%, p=0.04).

CONCLUSION

We found that SVR may lead to MHE resolution in a considerable proportion of patients, which has potential implications for disease prognosis.

Animal Naming Test - a simple and accurate test for diagnosis of minimal hepatic encephalopathy and prediction of overt hepatic encephalopathy

Aim of the study

Minimal hepatic encephalopathy (MHE) is the mildest form in the spectrum of hepatic encepha-lopathy (HE). We compared the usefulness of the Psychometric Hepatic Encephalopathy Score (PHES) and Animal Naming Test (ANT) for the diagnosis of MHE and the prediction of the development of overt episodes of HE.

Material and methods

103 consecutive patients with liver cirrhosis without overt HE were subjected to PHES and ANT evaluation. The receiver-operating characteristic curve was used to determine the optimum cut-off of the ANT value for the diagnosis of MHE.

Results

Thirty-seven (35.9%) patients had MHE as assessed by altered PHES. ANT (< 14) was positive in 36 (34.95%) patients with MHE with a sensitivity of 89.19% and specificity of 95.7%, positive predictive value (PPV) of 91.67%, negative predictive value (NPV) of 94.03% and diagnostic accuracy of 93.20%. The area under the curve for diagnosis of MHE was 0.978 (95% CI: 0.954-1.0). MHE patients had significantly lower ANT as compared to non-MHE patients and controls (10.81 ±0.324 vs. 15.27 ±0.147 vs. 15.78 ±0.192, respectively, p = 0.01). ANT correlated with PHES (r = 0.752, p = 0.001) and also with Child-Pugh (r = –0.408, p = 0.001) and MELD (r = –0.318, p = 0.001) scores. During follow-up, 14 patients in the MHE group and 4 in the non-MHE group developed overt episodes of HE (p = 0.001).

Conclusions

ANT is simple and accurate for the diagnosis of MHE and prediction of overt episodes of HE in patients with cirrhosis and correlates well with the Child-Pugh and MELD scores.

Epidemiology of Hepatic Encephalopathy

Hepatic encephalopathy (HE) is a complex condition with multiple causes each with varying degrees of severity. HE negatively impacts patients' quality of life, and it is associated with significant burdens to patients and their caregivers. The prevalence of cirrhosis, the most common risk factor for HE, has steadily increased during recent years. In turn, an upsurge in the clinical and health care burdens related to HE is expected in the upcoming years. This article provides a comprehensive review of the epidemiology of HE.

Role of Brain Biomarkers S-100-Beta and Neuron-Specific Enolase for Detection and Follow-Up of Hepatic Encephalopathy in Cirrhosis before, during and after Treatment with L-Ornithine-L-Aspartate

Introduction

Hepatic encephalopathy (HE), in the context of liver cirrhosis, seems to result from low-grade cerebral edema of the astrocytes. Serum brain biomarkers S-100-beta und neuron-specific enolase (NSE) are often elevated in brain injury. We hypothesized that neuromarkers S-100-beta and NSE can be used in the diagnosis of HE, compared with standardized diagnostic tools.

Material and Methods

A prospective non-randomized intervention study was performed using L-ornithine-L-aspartate (LOLA) for HE treatment. Primary endpoint was the evaluation of neuromarkers S-100-beta and NSE for detection and diagnosis of follow-up of HE. As secondary endpoints, the efficacy of LOLA on the course of HE and the diagnostic role of Portosystemic-Encephalopathy-Syndrome score (PHES) and critical flicker frequency (CFF) were analyzed. For diagnosis of covert (CHE) and overt (OHE) HE, West-Haven criteria (WHC), PHES and CFF were assessed at study entry. LOLA was applied (20 g i.v.) for 6 days. At the end of the study, HE evaluation was repeated. S-100-beta, NSE and ammonia were assessed in each patient before, during and after therapy with LOLA.

Results

30 patients were included. At study entry, CHE was diagnosed in 50% and OHE in 50% of all subjects. A total of 25 participants completed the study. After LOLA therapy, deterioration of HE occurred in <11%, while most patients showed improvement (e.g. improved CFF in 79%). No significant correlation with HE severity (as diagnosed by WHC, PHES and CFF) could be demonstrated for any biochemical parameter. In addition, there were no significant changes in brain biomarkers during the treatment period.

Discussion

While CFF as well as PHES showed good correlation with treatment response, S-100-beta and NSE did not significantly correlate with HE severity compared to proven diagnostic methods, and do not seem reliable biochemical markers for the follow-up under therapy.

Advances in psychometric tests for screening minimal hepatic encephalopathy: From paper-and-pencil to computer-aided assessment

Minimal hepatic encephalopathy (MHE) is a major neuropsychiatric complication of liver cirrhosis and portosystemic shunting. Although MHE produces a spectrum of cognitive impairments in the domains of short-term attention, working memory, and executive function, it generally does not present with obvious clinical manifestation on conventional assessments. Paper-and-pencil psychometric tests, such as the psychometric hepatic encephalopathy score and the repeatable battery for the assessment of neuropsychological status, are recommended to diagnose MHE. However, these tests are neither rapid nor convenient to use in practice. To facilitate repeated testing in clinic and follow-up, computer-aided psychometric tests, such as the scan test, Cognitive Drug Research assessment battery, inhibitory control test, EncephalApp Stroop App, and critical flicker frequency, have been used to screen for MHE among patients with liver cirrhosis. The aim of this review was to describe the progression from the utility of paper-and-pencil to computer-aided psychometric tests for MHE screening in clinical practice.

Influence of contrast-reversing frequency on the amplitude and spatial distribution of visual cortex hemodynamic responses

Visual stimulation is one of the most commonly used paradigms for cerebral cortex function investigation. Experiments typically involve presenting to a volunteer a black-and-white checkerboard with contrast-reversing at a frequency of 4 to 16 Hz. The aim of the present study was to investigate the influence of the flickering frequency on the amplitude of changes in the concentration of oxygenated and deoxygenated hemoglobin. The hemoglobin concentrations were assessed with the use of a high resolution diffuse optical tomography method. Spatial distributions of changes in hemoglobin concentrations overlaying the visual cortex are shown for various stimuli frequencies. Moreover, the hemoglobin concentration changes obtained for different source-detector separations (from 1.5 to 5.4 cm) are presented. Our results demonstrate that the flickering frequency had a statistically significant effect on the induced oxyhemoglobin changes (p < 0,001). The amplitude of oxy hemoglobin concentration changes at a frequency of 8 Hz was higher in comparison with that measured at 4 Hz :[median(25th-75thpercentiles) 1.24 (0.94-1.71) vs. 0.92(0.73-1.28)µM, p < 0.001]; 12 Hz:[1.24 (0.94-1.71) vs. 1.04 (0.78-1.32) µM, p < 0.001]; and 16 Hz:[1.24 (0.94-1.71) vs. 1.15(0.87-1.48) µM, p < 0.001]. No significant differences were observed between the size of an area of activation for various frequencies. The demonstrated superiority of 8 Hz over other frequencies can advance understanding of visual stimulations and help guide future fNIRS protocols.