Diagnostic and prognostic values of critical flicker frequency determination as new diagnostic tool for objective HE evaluation in patients undergoing TIPS implantation

Evaluating a Novel, Portable, Self-Administrable Device ("Beacon") That Measures Critical Flicker Frequency as a Test for Hepatic Encephalopathy

INTRODUCTION

We compared critical flicker frequency (CFF) thresholds obtained using a novel portable device "Beacon" with thresholds from the commercially available Lafayette Flicker Fusion System (Lafayette-FFS) in patients with cirrhosis.

METHODS

One hundred fifty-three participants with chronic liver disease underwent CFF testing using Beacon and Lafayette-FFS with a method-of-limits and/or forced-choice protocol.

RESULTS

Beacon demonstrated excellent test-retest reliability (intraclass correlation 0.91-0.97) and good correlation with the Lafayette-FFS values (intraclass correlation 0.77-0.84). Forced-choice CFF were on average 4.1 Hz higher than method-of-limits descending CFFs.

DISCUSSION

Beacon can be self-administered by patients with chronic liver disease and cirrhosis to measure CFF, a validated screening test for minimal hepatic encephalopathy.

Psychometric Hepatic Encephalopathy Score for the Diagnosis of Minimal Hepatic Encephalopathy in Thai Cirrhotic Patients

The psychometric hepatic encephalopathy score (PHES) is the gold standard for diagnosing minimal hepatic encephalopathy (MHE). Screening for MHE is frequently overlooked in clinical practice due to time constraints. Furthermore, the simplified animal naming test (S-ANT1) is a new simple tool for evaluating MHE in cirrhotic patients. The purpose of this study was to standardize the PHES in a healthy Thai population, assess the prevalence of MHE, and validate the S-ANT1 in detecting MHE in patients with cirrhosis. The study included 194 healthy controls and 203 cirrhotic patients without overt HE. Psychometric tests and the S-ANT1 were administered to all participants. Multiple linear regression was used to analyze factors related to PHES results, and formulas were developed to predict the results for each PHES subtest. In healthy controls, age and education were predictors of all five subtests. The PHES of the control group was −0.26 ± 2.28 points, and the threshold for detecting MHE was set at ≤ −5 points. The cirrhotic group had PHES values of −2.6 ± 3.1 points. Moreover, MHE was found to be present in 26.6% of cirrhotic patients. S-ANT1 had a moderate positive correlation with PHES (r = 0.44, p < 0.001). S-ANT1 < 22 named animals detected MHE with a sensitivity of 71.2%, specificity of 65%, and area under the receiver operating curve of 0.68 (p < 0.001). In conclusion, Thai PHES normative data have been developed to detect MHE in cirrhotic patients who do not have overt HE. The optimal cutoff for detecting MHE in Thai cirrhotic patients was PHES ≤ −5 points and S-ANT1 < 22 named.

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.

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.

Predictors of Occurrence and Risk of Hepatic Encephalopathy After TIPS Creation: A 15-Year Experience

PURPOSE

To identify clinical variables, including use of newer Viatorr TIPS endoprosthesis with controlled expansion (VCX) that may affect the occurrence and risk of hepatic encephalopathy after transjugular intrahepatic portosystemic shunt (TIPS) creation.

METHODS

A total of 376 patients who underwent TIPS creation at our institution between 2003 and 2018 were retrospectively identified. Of these patients, 71 received a Viatorr controlled expansion endoprosthesis and 305 received a Viatorr TIPS endoprosthesis (older version without controlled expansion). Multivariate regression analysis was used to identify factors predicting the occurrence of hepatic encephalopathy after TIPS creation; a Cox proportional hazard model was used to assess risk of HE through time to HE onset RESULTS: A total of 194 patients (52%) developed hepatic encephalopathy after TIPS creation, including 28 of 71 patients (39%) who received a VCX endoprosthesis. Older patient age and the use of Viatorr endoprosthesis without controlled expansion were significantly associated with the development of hepatic encephalopathy overall. Pre-TIPS pressure variables, patient age, plasma international normalized ratio, and model for end-stage liver disease score were risk factors for time to hepatic encephalopathy.

CONCLUSION

Several variables are mild predictors of early hepatic encephalopathy development after TIPS creation, and the use of VCX endoprosthesis in TIPS creation is associated with a modest lower risk of hepatic encephalopathy. These preliminary findings should be considered in regard to patient selection, endoprosthesis selection, and post-transjugular intrahepatic portosystemic shunt creation monitoring for the development of hepatic encephalopathy.

Outcomes in Clinical Trials Evaluating Interventions for the Prevention and Treatment of Hepatic Encephalopathy

Randomised clinical trials and systematic reviews of research findings can provide high-quality evidence for decision-making in the management of patients with hepatic encephalopathy. A large number of clinical trials have been undertaken, over the last 50 years, relative to the prevention and treatment of this condition. However, changes have been made, during this time, in the classification of hepatic encephalopathy, diagnostic criteria and assessment measures. These temporally based changes and the consequent lack of standardisation make it difficult to compare interventions and to evaluate their comparative efficacy and safety. While some consensus has been reached in relation to the diagnostic evaluation, classification and monitoring of patients in clinical trials, there is less surety about the choice of clinical endpoints. These outcome measures should be universally applicable, easily measured and clinically relevant. This article reviews the current recommendations regarding outcome selection and outlines some of the potential problems and pitfalls inherent in clinical trial evaluating interventions for the management of hepatic encephalopathy.

Critical flicker frequency test predicts overt hepatic encephalopathy and survival in patients with liver cirrhosis

BACKGROUND

A critical flicker frequency (CFF) ≤39 Hz identifies cirrhotic patients with minimal hepatic encephalopathy (mHE) and predicts the risk of both overt hepatic encephalopathy (oHE) and mortality in patients with previous episodes of decompensation and/or oHE.

AIMS

Herein, we evaluated the effectiveness of CFF in predicting the first episode of oHE and survival in cirrhotics who had never experienced an episode of oHE.

METHODS

Our cohort study of 134 patients and 150 healthy subjects were examined. A CFF > 39 Hz was considered normal and pathological when ≤39 Hz. The median follow up was 36 months.

RESULTS

At baseline, all controls had CFF > 39 Hz. Ninety-three patients had a CFF > 39 Hz and 41 had a CFF ≤ 39 Hz. The prevalence of CFF ≤ 39 Hz significantly increased with the progression of the Child-Pugh class (p = 0.003). Moreover, the risk of oHE was increased by CFF ≤ 39 (p < 0.001, by log-rank test) [HR = 7.57; CI(3.27-17.50); p < 0.0001, by Cox model] and ammonia [HR = 1.02 CI(1.01-1.03), p = 0.0009]. Both a CFF value ≤ 39 Hz and Child-Pugh class were independent predictors of mortality by Cox model [HR = 1.97; CI(1.01-3.95), p = 0.049; HR = 3.85 CI(1.68-8.83), p = 0.003].

CONCLUSIONS

CFF predicts the first episode of oHE in cirrhotics that had never experienced oHE, and predicts mortality risk. These findings suggest that cirrhotic patients should be routinely screened by CFF.

Neuropsychiatric performance in patients with cirrhosis: Who is "normal"?

In patients with cirrhosis a normal neuropsychiatric performance has been traditionally defined by the absence of any degree of hepatic encephalopathy and/or the absence of psychometric or neurophysiological abnormalities, compared with data from the healthy population. As the understanding and management of end-stage liver disease continues to change, it is our impression that the concept of normal neuropsychiatric performance also needs updating. This review explores novel and more pragmatic interpretations of neuropsychiatric "normality" compared with top personal performance, in terms of risk of overt hepatic encephalopathy or brain failure and in relation with events such as liver transplantation, decompensation, acute-on-chronic liver failure and transjugular intrahepatic portosystemic shunt placement.

Hepatic encephalopathy: what the multidisciplinary team can do

Hepatic encephalopathy (HE) is a complex disease requiring a multidisciplinary approach among specialists, primary care team, family, and caregivers. HE is currently a diagnosis of exclusion, requiring an extensive workup to exclude other possible etiologies, including mental status changes, metabolic, infectious, traumatic, and iatrogenic causes. The categorization of HE encompasses a continuum, varying from the clinically silent minimal HE (MHE), which is only detectable using psychometric tests, to overt HE, which is further divided into four grades of severity. While there has been an increased effort to create fast and reliable methods for the detection of MHE, screening is still underperformed due to the lack of standardization and efficient methods of diagnosis. The management of HE requires consultation from various disciplines, including hepatology, primary care physicians, neurology, psychiatry, dietician/nutritionist, social workers, and other medical and surgical subspecialties based on clinical presentation and clear communication among these disciplines to best manage patients with HE throughout their course. The first-line therapy for HE is lactulose with or without rifaximin. Following the initial episode of overt HE, secondary prophylaxis with lactulose and/or rifaximin is indicated with the goal to prevent recurrent episodes and improve quality of life. Recent studies have demonstrated the negative impact of MHE on quality of life and clinical outcomes. In light of all this, we emphasize the importance of screening and treating MHE in patients with liver cirrhosis, particularly through a multidisciplinary team approach.

Qualifying and quantifying minimal hepatic encephalopathy

Minimal hepatic encephalopathy is the term applied to the neuropsychiatric status of patients with cirrhosis who are unimpaired on clinical examination but show alterations in neuropsychological tests exploring psychomotor speed/executive function and/or in neurophysiological variables. There is no gold standard for the diagnosis of this syndrome. As these patients have, by definition, no recognizable clinical features of brain dysfunction, the primary prerequisite for the diagnosis is careful exclusion of clinical symptoms and signs. A large number of psychometric tests/test systems have been evaluated in this patient group. Of these the best known and validated is the Portal Systemic Hepatic Encephalopathy Score (PHES) derived from a test battery of five paper and pencil tests; normative reference data are available in several countries. The electroencephalogram (EEG) has been used to diagnose hepatic encephalopathy since the 1950s but, once popular, the technology is not as accessible now as it once was. The performance characteristics of the EEG are critically dependent on the type of analysis undertaken; spectral analysis has better performance characteristics than visual analysis; evolving analytical techniques may provide better diagnostic information while the advent of portable wireless headsets may facilitate more widespread use. A large number of other diagnostic tools have been validated for the diagnosis of minimal hepatic encephalopathy including Critical Flicker Frequency, the Inhibitory Control Test, the Stroop test, the Scan package and the Continuous Reaction Time; each has its pros and cons; strengths and weaknesses; protagonists and detractors. Recent AASLD/EASL Practice Guidelines suggest that the diagnosis of minimal hepatic encephalopathy should be based on the PHES test together with one of the validated alternative techniques or the EEG. Minimal hepatic encephalopathy has a detrimental effect on the well-being of patients and their care-givers. It responds well to treatment with resolution of test abnormalities and the associated detrimental effects on quality of life, liver-related mortality and morbidity. Patients will only benefit in this way if they can be effectively diagnosed. Corporate efforts and consensus agreements are needed to develop effective diagnostic algorithms.

Diagnosing covert hepatic encephalopathy

NOTE: Could not find interview file for this one by Lauridsen and Vilstrup; thought we had this, but it was just LAU, so mistakenly saw this as Lauridsen when I scan files. Can you confirm they were filmed at AASLD 2014?

Severe liver fibrosis caused by Schistosoma mansoni: management and treatment with a transjugular intrahepatic portosystemic shunt

Liver diseases are common in inhabitants and migrants of tropical countries, where the liver can be exposed not only to toxins but also to many viral, bacterial, fungal, and parasitic infections. Schistosomiasis--a common parasitic infection that affects at least 240 million people worldwide, mostly in Africa--is regarded as the most frequent cause of liver fibrosis worldwide. We present a case of a 19-year-old male refugee from Guinea with recurrent oesophageal variceal bleeding due to schistosomal liver fibrosis refractory to endoscopic therapy. This case was an indication for portosystemic surgery, which is a highly invasive non-reversible intervention. An alternative, less invasive, reversible radiological procedure, used in liver cirrhosis, is the placement of a transjugular intrahepatic portosystemic shunt (TIPS). After thorough considerations of all therapeutic options we placed a TIPS in our patient. In more than 3 years of observation, he is clinically well apart from one episode of hepatic encephalopathy related to an acute episode of viral gastroenteritis. Bleeding from oesophageal varices has not recurred. In this Grand Round, we review the diagnostic approaches and treatment options for portal hypertension due to schistosomal liver fibrosis.

Diagnosis of minimal hepatic encephalopathy

Minimal hepatic encephalopathy (mHE) has significant impact upon a liver patient's daily living and health related quality of life. Therefore a majority of clinicians agree that mHE should be diagnosed and treated. The optimal means for diagnosing mHE, however, is controversial. This paper describes the currently most frequently used methods-EEG, critical flicker frequency, Continuous Reaction time Test, Inhibitory Control Test, computerized test batteries such as the Cognitive Drug Research test battery, the psychometric hepatic encephalopathy score (PHES) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)-and their pros and cons.

Progress in diagnosis of minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) is defined as HE without symptoms on clinical/neurological examination, but with deficits in some cognitive areas that can only be measured by neuropsychometric testing. MHE is associated with reduced quality of working, driving, memory, and cognitive function, and is a risk factor for the development of overt HE. Compared with non-MHE patients, MHE patients have a high mortality rate, so positive screening and intervention in patients with MHE are needed to improve the quality of life in patients with cirrhosis and reduce traffic accidents and the social burden of medical care. The current approach to the diagnosis of MHE includes mental scales (paper pencil test, computer test, or the combination of the two), electrophysiological examination, and imaging examination. Diagnosis of MHE is still a challenge now, and it is needed to establish a better clinical diagnosis standard to improve the diagnostic level.

Useful tests for hepatic encephalopathy in clinical practice

Hepatic encephalopathy (HE) is a serious complication of liver disease and portosystemic shunting that represents a continuum of neuropsychiatric changes and altered consciousness. It is classified as overt HE (OHE) when clinically apparent or as covert HE (CHE) in its mildest form. Progression of CHE to OHE and its impact of quality of life make its early diagnosis imperative. Several diagnostic techniques ranging from simple clinical scales to sophisticated computerized tests exist, yet diagnosis remains a challenge, due to the time, cost, and personnel involved. Psychometric tests appear promising due to their high sensitivity and low cost, but results are variable depending on age and education. The pros and cons of current diagnostic methods for OHE and CHE are reviewed, along with strategy for CHE testing.

Neurologic manifestations of acute and chronic liver disease

PURPOSE OF REVIEW

This article summarizes the most common neurologic sequelae of acute and chronic liver failure, liver transplantation, and other treatments for liver disease, and outlines the pathogenesis, neurologic manifestations, and treatment of Wilson disease.

RECENT FINDINGS

The neurologic manifestations of liver disease are caused by the liver's failure to detoxify active compounds that have deleterious effects on the central and peripheral nervous systems. In addition, treatments for liver disease such as liver transplantation, transjugular intrahepatic portosystemic shunt, and antiviral medications can also be neurotoxic. Wilson disease affects the liver and nervous system simultaneously and may often initially be diagnosed by a neurologist; treatment options have evolved over recent years.

SUMMARY

Acute and chronic liver diseases are encountered commonly in the general population. Neurologic dysfunction will eventually affect a significant number of these individuals, especially if the disease progresses to liver failure. Early recognition of these neurologic manifestations can lead to more effective management of these patients.

Value of critical flicker frequency and psychometric hepatic encephalopathy score in diagnosis of low-grade hepatic encephalopathy

BACKGROUND & AIMS

Critical flicker frequency (CFF) and psychometric hepatic encephalopathy score (PHES) analyses are widely used to diagnose hepatic encephalopathy (HE), but little is known about their value in the diagnosis of low-grade HE.

METHODS

The diagnostic values of CFF and PHES were compared using a computerized test battery and West Haven criteria as reference. We performed CFF analysis on 559 patients with cirrhosis and 261 without (controls). Of these 820 patients, 448 were evaluated using a modified PHES system and 148 were also evaluated using the conventional PHES system.

RESULTS

CFF distinguished between patients with overt HE and without minimal or overt HE in the entire study population with 98% sensitivity and 94% specificity and in the subgroup of patients who were evaluated by conventional PHES with 97% sensitivity and 100% specificity. Conventional PHES identified patients with overt HE with 73% sensitivity and 89% specificity. CFF distinguished between patients with and without minimal HE with only 37% sensitivity but 94% specificity (entire study population). In the subgroup of patients evaluated by conventional PHES, CFF distinguished between patients with and without minimal HE with 22% sensitivity and 100% specificity; these values were similar to those for conventional PHES (30% sensitivity and 89% specificity). The modified PHES distinguished between patients with and without minimal HE with 49% sensitivity and 74% specificity. The diagnostic agreement values between CFF and conventional or modified PHES in patients with minimal HE were only 54% or 47%, respectively.

CONCLUSIONS

In an analysis of patients with cirrhosis and controls, CFF distinguished between patients with overt HE and without minimal or overt HE. PHES testing produced a statistically significant difference among groups, but there was considerable overlap between controls and patients with overt HE. PHES, CFF, and a combination of PHES and CFF could not reliably distinguish patients with minimal HE from controls or those with overt HE.

Pre-transjugular intrahepatic portosystemic shunts (TIPS) prediction of post-TIPS overt hepatic encephalopathy: the critical flicker frequency is more accurate than psychometric tests

Transjugular intrahepatic portosystemic shunts (TIPS) is a second-line treatment because of an increased incidence of overt hepatic encephalopathy (OHE). A better selection of patients to decrease this risk is needed and one promising approach could be the detection of minimal hepatic encephalopathy (MHE). The aim of the present prospective study was to determine whether pre-TIPS minimal hepatic encephalopathy was predictive of post-TIPS OHE and to compare Psychometric Hepatic Encephalopathy Sum Score(PHES) and the Critical Flicker Frequency (CFF) in this setting. From May 2008 to January 2011, 54 consecutive patients treated with TIPS were included. PHES and CFF were performed 1 to 7 days before and after TIPS at months 1, 3, 6, 9, and 12 or until liver transplantation or death. Before TIPS, MHE was detected by PHES and CFF in 33% and 39% of patients, respectively. After the TIPS procedure, 19 patients (35%) experienced a total of 64 episodes of OHE. OHE developed significantly more often inpatients for whom an indication for TIPS had been refractory ascites, with a history of OHE or of renal failure, lower hemoglobin level, or MHE as diagnosed by CFF. Post-TIPS OHE was more accurately predicted by CFF than by PHES. Absence of MHE at CFF had a good negative predictive value (91%) for the risk of post-TIPS recurrent OHE, defined as the occurrence of three or more episodes of OHE or of one episode which lasted more than 15 days. The absence of pre-TIPS history of OHE and a CFF value equal to or greater than 39 Hz had a 100% negative predictive value for post-TIPS recurrent OHE.

CONCLUSION

Aiming to decrease the rate of post-TIPS HE, the use of CFF could help selecting patients for TIPS.

TIPS: 25 years later

In the 25 years since the first TIPS intervention has been performed, technical standards, indications, and contraindications have been set up. The previous considerable problem of shunt failure by thrombosis or intimal proliferation in the stent or in the draining hepatic vein has been reduced considerably by the availability of polytetrafluoroethylene (PTFE)-covered stents resulting in reduced rebleeding and improved survival. Unfortunately, most clinical studies have been performed prior to the release of the covered stent and, therefore, do not represent the present state of the art. In spite of this, TIPS has gained increasing acceptance in the treatment of the various complications of portal hypertension and vascular diseases of the liver.

Assessment and usefulness of clinical scales for semiquantification of overt hepatic encephalopathy

Hepatic encephalopathy (HE) represents the effects of liver dysfunction on the brain. When HE is clinically obvious (eg, confusion, poor judgment, personality change), it is termed overt HE. The severity of HE is measured by different methods. Assessing the severity of HE is important for determining patient prognosis and effectiveness of therapy. This article discusses the different methods for grading HE, including clinical rating scales, neuropsychological tests, and neurophysiologic measures.

Pathogenesis, diagnosis, and treatment of hepatic encephalopathy

Hepatic encephalopathy (HE) is a neuropsychiatric disorder seen in patients with advanced liver disease or porto-systemic shunts. Based on etiology and severity of HE, the World Congress of Gastroenterology has divided HE into categories and sub-categories. Many user-friendly computer-based neuropsychiatric tests are being validated for diagnosing covert HE. Currently, emphasis is being given to view HE deficits as a continuous spectrum rather than distinct stages. Ammonia is believed to play crucial role in pathogenesis of HE via astrocyte swelling and cerebral edema. However, evidence has been building up which supports the synergistic role of oxidative stress, inflammation and neurosteroids in pathogenesis of HE. At present, treatment of HE aims at decreasing the production and intestinal absorption of ammonia. But as the role of new pathogenetic mechanisms becomes clear, many potential new treatment strategies may become available for clinician.

Critical flicker frequency and continuous reaction times for the diagnosis of minimal hepatic encephalopathy: a comparative study of 154 patients with liver disease

Minimal hepatic encephalopathy (MHE) is intermittently present in up to 2/3 of patients with chronic liver disease. It impairs their daily living and can be treated. However, there is no consensus on diagnostic criteria except that psychometric methods are required. We compared two easy-to-perform reproducible bedside methods: the critical flicker frequency (CFF) and continuous reaction times (CRT) tests. A CFF <39 Hz and CRT-index <1.9 (index: the ratio 50/(90 minus 10) percentiles of reaction times) indicates cerebral dysfunction. 154 patients with acute or chronic liver disease with out overt hepatic encephalopathy (HE) underwent both tests at the same occasion. Both tests were abnormal in 20% of the patients and both tests were normal in 40% of the patients. In more than 1/3 the two tests were not in agreement as CFF classified 32% and CRT-index classified 48% of the patients as having MHE (p < 0.005). The two tests were weakly linearly correlated (r(2) = 0.14, p < 0.001) and neither test correlated with the metabolic liver function measured by the Galactose Elimination Capacity (GEC), nor with the blood ammonia concentration. Both tests identified a large fraction of the patients as having MHE and cleared only 40%. The two tests did not show concordant results, likely because they describe different aspects of MHE: the CFF gives a measure of astrocytic metabolic state and hence pathogenic aspects of MHE, whereas the CRT measures a composite key performance, viz. the ability of reacting appropriately to a sensory stimulus. The choice of test depends on the information needed in the clinical and scientific care and study of the patients.

Mechanisms, diagnosis and management of hepatic encephalopathy

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication of both acute and chronic liver disease. Symptoms of HE can include confusion, disorientation and poor coordination. A general consensus exists that the synergistic effects of excess ammonia and inflammation cause astrocyte swelling and cerebral edema; however, the precise molecular mechanisms that lead to these morphological changes in the brain are unclear. Cerebral edema occurs to some degree in all patients with HE, regardless of its grade, and could underlie the pathogenesis of this disorder. The different grades of HE can be diagnosed by a number of investigations, including neuropsychometric tests (such as the psychometric hepatic encephalopathy score), brain imaging and clinical scales (such as the West Haven criteria). HE is best managed by excluding other possible causes of encephalopathy alongside identifying and the precipitating cause, and confirming the diagnosis by a positive response to empiric treatment. Empiric therapy for HE is largely based on the principle of reducing the production and absorption of ammonia in the gut through administration of pharmacological agents such as rifaximin and lactulose, which are approved by the FDA for the treatment of HE.