Subcortical impairment in subclinical hepatic encephalopathy

Clinical neurophysiology of hepatic encephalopathy

BACKGROUND/OBJECTIVES

Hepatic encephalopathy (HE) has relevant impact on the quality of life of patients and their caregivers and causes relevant costs because of hospitalizations and work days lost. Its quantification is important to perform adequate clinical trials on this relevant complication of cirrhosis and portal-systemic shunting. Clinical neurophysiology, which detects functional alterations of the nervous system, has been applied to the study of HE for over 60 years. This review aims at summarizing and clarifying the role of neurophysiologic techniques in the study of HE.

METHODS

A narrative review was performed aiming at interpreting the cited papers and the techniques on the basis of their physiological and pathophysiological meaning.

RESULTS

The potential role of EEG, quantified EEG, evoked potentials-both exogenous, endogenous and motor-have been clarified to the reader that may be unfamiliar with neurophysiology.

CONCLUSIONS

The EEG, reflecting the oscillatory changes of neural network is the preferable tool to detect and monitor HE, with the exception of its most severe stage, when EEG flattens. SSEP and MEP have indication to detect and monitor transmission alterations that are likely related to myelin changes and microedema.

Neurophysiological investigations of hepatic encephalopathy: ISHEN practice guidelines

By studying neuronal activity through neuronal electrogenesis, neurophysiological investigations provide a functional assessment of the nervous system and, therefore, has been used for quantitative assessment and follow-up of hepatic encephalopathy (HE). The different clinical neurophysiological approaches can be classified depending on the function to explore and their sensitivity to HE. The reliable techniques are those that reflect cortical function, i.e., cognitive-evoked potentials (EPs) (P300 paradigm), electroencephalogram (EEG), visual EPs (latency>100 ms) and somatosensory EPs (SEPs) (latency between 25 and 100 ms). Short-latency EPs (brainstem acoustic EPs, SEPs of a latency<25 ms) are in principle insensitive to HE, but can disclose brainstem conduction deficits due to oedema. SEPs and motor EPs can disclose myelopathies. Because of its parallelism to the clinical examination, clinical neurophysiology can complement the neurological examination: (i) to provide evidence of HE in patients who have normal consciousness; (ii) to rule out, at least under some conditions, disturbances of consciousness due to other causes (e.g. drug-induced disturbances, non-convulsive status epilepticus) with the reservation that the mildest degrees of encephalopathy might be associated with an EEG pattern similar to that induced by drugs; and (iii) to demonstrate the worsening or, conversely improvement, of HE in the follow-up period.

Cognitive impairment in people diagnosed with end-stage liver disease evaluated for liver transplantation

Cognitive impairments are common in patients with end-stage liver disease (ESLD). The aim of the present study was to identify and characterize the neuropsychological deficits between groups of patients with a variety of causes of ESLD and to assess the impact of heavy alcohol use on cognitive functioning. Cognitive functioning in 300 consecutive outpatients presenting for liver transplantation evaluation was assessed using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). All patients underwent a psychiatric interview and a physical and laboratory assessment. The prevalence of neuropsychological impairment was highest among patients with liver disease secondary to alcohol. Poor performance on neuropsychological testing was correlated strongly with the severity of liver disease as measured by the model for end-stage liver disease (MELD). After controlling for the linear effects of MELD in subsequent analysis, a group difference emerged in patients with cholestatic liver disease showing less cognitive impairment when compared to all other groups. After controlling for the severity of liver disease, those patients with a history of alcohol abuse or dependence were found to perform more poorly on neuropsychological testing than those patients without such a history. Furthermore, the presence of these cognitive impairments predicted disability independent of the severity of the underlying liver disease.

Neurophysiological investigation of hepatic encephalopathy

The neurophysiological tools used to study hepatic encephalopathy (HE) are the electroencephalogram (EEG) and the evoked potentials (EPs), both exogenous and endogenous. These tools are used (1) to diagnose HE in patients with severe liver disease and mental alteration, (2) to grade overt HE and monitor the effect of treatment for HE, (3) to diagnose minimal HE (4) to predict the occurrence of episodes of overt HE or liver-related death. The rationale for the use of each of these tools together with their theoretical and practical role is reviewed.

Effects of hepatic function and hepatitis C virus on the nervous system assessment of advanced-stage HIV-infected individuals

OBJECTIVES

To examine the effects of liver function and hepatitis C virus (HCV) serostatus on neurological, neuropsychological, and psychiatric abnormalities in an advanced-stage HIV-infected cohort.

DESIGN

A correlational analysis of baseline data accumulated on 137 participants in the Manhattan HIV Brain Bank, a longitudinal study of HIV-infected individuals.

METHODS

Patients underwent a battery of neuropsychological tests, a semi-structured psychiatric interview, and a neurological examination. The resulting diagnostic data were correlated with biochemical indices of hepatic function and HCV serostatus.

RESULTS

Biochemical indices of liver function correlated with motor dysfunction determined by neurological evaluation, but not with neuropsychological or psychiatric disorders. Discrete neurological diagnostic entities showed no relationship with biochemical indices, with one exception: patients with cryptococcal leptomeningitis had worse liver function than those without. HCV had no relationship with any neurological disorder or symptom complex. In contrast, HCV serostatus was related to neuropsychological and psychiatric abnormalities, and indices of liver function were not. HCV-seropositive patients were more likely to have histories of opiate, cocaine or stimulant dependency, to have greater impairment in executive functioning, and to meet diagnostic criteria for AIDS dementia, compared with HCV-negative individuals of similar immunological and virological status.

CONCLUSIONS

HCV and biochemical indices of liver function associate differentially with nervous system abnormalities in this HIV-infected population. Neurological abnormalities correlate with biochemical indices of liver function, whereas neuropsychological and psychiatric dysfunction are linked to HCV infection. We postulate that multifactorial impacts of HCV and liver disease on HIV-related nervous system disorders may originate in different anatomical and cellular compartments.

Methods for diagnosing hepatic encephalopathy in patients with cirrhosis: a multidimensional approach

There is no "gold standard" for diagnosing hepatic encephalopathy in patients with cirrhosis. In consequence, the presence of this condition, unless floridly overt, is often missed. As a result, the majority of patients are denied the benefits of treatment. There are a number of individual techniques, which access different aspects of cerebral function that can be used, singly or in combination, to provide diagnostic information in this condition, including mental state assessment, psychometric testing, electroencephalography, sensory and cognitive evoked potentials, and neuroimaging. These have been variously applied to the study of hepatic encephalopathy but fundamental differences in the essential aims of the studies, as well as differences in the patient populations and the acquisition and analysis of the data, have made comparisons difficult. Thus, there is no clear consensus as to the sensitivity, specificity, or validity of these tests when used alone or in combination. There are, however, a number of additional methods that could be used to analyze the electrophysiological data, and a number of alternative evoked potentials that could be measured to provide better diagnostic information. In addition, there are a number of techniques, such as critical flicker frequency and smooth pursuit eye movements, which have not yet been applied systematically in this condition and which may provide useful diagnostic information. Clearly the methods for assessing hepatic encephalopathy need to be reviewed, newer methods for analyzing the electrophysiological data and newer techniques for assessing alternative aspects of cerebral function need to be explored for their diagnostic utility. This process should aim at developing a multidimensional diagnostic tool.

Characteristics of minimal hepatic encephalopathy

The term minimal hepatic encephalopathy refers to the subtle changes in cognitive function, electrophysiological parameters, cerebral neurochemical/neurotransmitter homeostasis, cerebral blood flow, metabolism, and fluid homeostasis that can be observed in patients with cirrhosis who have no clinical evidence of hepatic encephalopathy. Use of this term emphasizes the fact that the entity of hepatic encephalopathy is a single syndrome with quantitatively distinct features relating to severity. The absence of clinical evidence of hepatic encephalopathy is key to the diagnosis and can only be determined by a detailed assessment of the patients' history and a comprehensive neurological assessment of consciousness, cognitive, and motor function. The neuropsychological features of minimal hepatic encephalopathy point to a disorder of executive functioning, particularly selective attention and psychomotor speed, but other abnormalities may be observed. Alterations in electrophysiological variables have been described; endogenous evoked potentials are, in principle, more likely to reflect the presence of minimal hepatic encephalopathy, since they reflect cognitive phenomena rather than mere stimulus conduction but the specificity of the changes observed is unclear at present. Changes have also been described in the execution of diadochokinetic movements and in the capacity to discriminate flickering light, both of which may have diagnostic potential. The changes observed in cerebral blood flow and metabolism in SPET, PET, and 1H and 31P MRS studies reflect the pathogenic process that underlies the condition rather than providing diagnostic information. Similarly, the morphological brain abnormalities identified in this population, including mild brain oedema, hyperintensity of the globus pallidus and other subcortical nuclei observed in cerebral MR studies, and the central and cortical atrophy observed in neural imaging studies, are unlikely to have diagnostic utility. The presence of minimal hepatic encephalopathy is not without clinical consequence; it has a detrimental effect on health-related quality of life, the ability to perform complex tasks such as driving, and on outcome.

Minimal hepatic encephalopathy and extrapyramidal signs in patients with cirrhosis

OBJECTIVE

Two types of neurological dysfunction can occur in compensated cirrhosis: 1) extrapyramidal signs related to the accumulation of manganese in the basal ganglia and 2) milder degrees of cognitive impairment known as minimal hepatic encephalopathy (mHE). We assessed whether there was any relationship between both disorders in 42 patients with compensated cirrhosis.

METHODS

Minimal hepatic encephalopathy was diagnosed using a battery of manual neuropsychological tests. Cognitive functioning was assessed by the Mini-Mental State Examination. Extrapyramidal signs were evaluated by the Columbia scale.

RESULTS

Minimal hepatic encephalopathy was diagnosed in 15 (35.7%) patients. A total of 52.4% of patients showed significant extrapyramidal signs. Scores for the Columbia scale were higher in the presence of mHE (mean +/- SD, 16.0 +/- 10.9 vs 5.3 +/- 7.1, p = 0.0004). In the bivariate analysis, mHE, Child-Pugh score, and Mini-Mental State Examination score were significantly associated with extrapyramidal signs, whereas in the multivariate analysis, mHE was the only independent variable related to extrapyramidal signs.

CONCLUSIONS

There was a link between extrapyramidal signs and diagnosis of mHE based on manual neuropsychological testing. This finding may be explained by the influence of extrapyramidal manifestations on test performance or by a real pathophysiological relationship between both disorders. Further studies are necessary to resolve this question.

Hepatic encephalopathy

In the last decade, a significant amount of research has been devoted to the pathogenesis and treatment of hepatic encephalopathy (HE). Non-invasive neuroimaging techniques such as magnetic resonance imaging and spectroscopy have become important research tools. The search for a suitable animal model of HE associated with cirrhosis is still ongoing. Moreover, consensus terminology and diagnostic criteria for HE in humans are badly needed.