Visual attention orienting in liver cirrhosis without overt hepatic encephalopathy

The PHES battery does not detect all cirrhotic patients with early neurological deficits, which are different in different patients

Background and aims

The psychometric hepatic encephalopathy score (PHES) is the “gold standard” for minimal hepatic encephalopathy (MHE) diagnosis. Some reports suggest that some cirrhotic patients “without” MHE according to PHES show neurological deficits and other reports that neurological alterations are not homogeneous in all cirrhotic patients. This work aimed to assess whether: 1) a relevant proportion of cirrhotic patients show neurological deficits not detected by PHES; 2) cirrhotic patients with mild neurological deficits are a homogeneous population or may be classified in sub-groups according to specific deficits.

Methods

Cirrhotic patients “without” (n = 56) or “with” MHE (n = 41) according to PHES and controls (n = 52) performed psychometric tests assessing attention, concentration, mental processing speed, working memory and bimanual and visuomotor coordination. Heterogeneity of neurological alterations was analysed using Hierarchical Clustering Analysis.

Results

PHES classified as “with” MHE 42% of patients. Around 40% of patients “without” MHE according to PHES fail two psychometric tests. Oral SDMT, d2, bimanual and visuo-motor coordination tests are failed by 54, 51, 51 and 43% of patients, respectively. The earliest neurological alterations are different for different patients. Hierarchical clustering analysis shows that patients “without” MHE according to PHES may be classified in clusters according to the tests failed. In some patients coordination impairment appear before cognitive impairment while in others concentration and attention deficits appear before.

Conclusions

PHES is not sensitive enough to detect early neurological alterations in a relevant proportion of cirrhotic patients. Oral SDMT, d2 and bimanual and visuo-motor coordination tests are more sensitive. The earliest neurological alterations are different in different cirrhotic patients. These data also have relevant clinical implications. Patients classified as “without MHE” by PHES belonging to clusters 3 and 4 in our study have a high risk of suffering clinical complications, including overt HE and must be diagnosed and clinically followed.

Patients with minimal hepatic encephalopathy show impaired mismatch negativity correlating with reduced performance in attention tests

Attention deficit is an early event in the cognitive impairment of patients with minimal hepatic encephalopathy (MHE). The underlying mechanisms remain unclear. Mismatch negativity (MMN) is an auditory event-related potential that reflects an attentional trigger. Patients with schizophrenia show impaired attention and cognitive function, which are reflected in altered MMN. We hypothesized that patients with MHE, similarly to those with schizophrenia, should show MMN alterations related with attention deficits. The aims of this work were to assess whether (1) MMN is altered in cirrhotic patients with MHE, compared to those without MHE, (2) MMN changes in parallel with performance in attention tests and/or MHE in a longitudinal study, and (3) MMN predicts performance in attention tests and/or in the Psychometric Hepatic Encephalopathy Score (PHES). We performed MMN analysis as well as attention and coordination tests in 34 control subjects and in 37 patients with liver cirrhosis without MHE and 23 with MHE. Patients with MHE show reduced performance in selective and sustained attention tests and in visuomotor and bimanual coordination tests. The MMN wave area was reduced in patients with MHE, but not in those without MHE. In the longitudinal study, MMN area improved in parallel with performance in attention tests and PHES in 4 patients and worsened in parallel in another 4. Logistic regression analyses showed that MMN area predicts performance in attention tests and in PHES, but not in other tests or critical flicker frequency. Receiver operating characteristic curve analyses showed that MMN area predicts attention deficits in the number connection tests A and B, Stroop tasks, and MHE, with sensitivities of 75%-90% and specificities of 76%-83%.

CONCLUSION

MMN area is useful to diagnose attention deficits and MHE in patients with liver cirrhosis.

Top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients: An ERP study

OBJECTIVE

This study aims to evaluate the efficiency of top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients without overt hepatic encephalopathy (HE).

METHODS

Reaction times (RTs), accuracy and event-related potentials (ERPs) were recorded during the execution of a visual Simon task in 17 cirrhotic patients and 10 healthy controls. Amplitude and latency of the P1 and N1 (indexes of bottom-up processes) and of the N2pc (index of top-down processes) were measured.

RESULTS

Patients were slower than controls, and patients with minimal HE (MHE) were slower than patients without MHE. The distribution analysis of RTs showed that the Simon effect decays with slower RTs in all the groups and that the shape of the distribution was different in MHE patients. No differences were found between cirrhotic patients and controls for P1 and N1 amplitude and latency. In contrast, N2pc latency was delayed in cirrhotic patients compared to controls independently of MHE.

CONCLUSIONS

In the extrastriate cortex of cirrhotic patients without HE, top-down processes are altered whereas bottom-up processes are preserved.

SIGNIFICANCE

The analysis of exogenous and endogenous visual components of ERPs provides a model to study the functional dissociation between top-down and bottom-up processes inside the extrastriate cortex.

Disruption of smooth pursuit eye movements in cirrhosis: relationship to hepatic encephalopathy and its treatment

Smooth pursuit eye movements (SPEM) are the conjugate movements used to track the smooth trajectory of small dots. Jerky or 'saccadic' ocular pursuit has been reported in patients with cirrhosis, but no formal assessment of SPEM has ever been undertaken. The aim of this study was to evaluate SPEM in patients with cirrhosis and varying degrees of hepatic encephalopathy. The patient population comprised 56 individuals (31 men, 25 women) of mean age 51.1 (range, 25-70) years, with biopsy-proven cirrhosis, classified, using clinical, electroencephalographic, and psychometric variables, as either neuropsychiatrically unimpaired or as having minimal or overt hepatic encephalopathy; patients were further categorized in relation to their treatment status. The reference population comprised 28 healthy volunteers (12 men, 16 women) of mean age 47.3 (range, 26-65) years. SPEM was assessed using an electro-oculographic technique. Visual inspection of the SPEM recordings showed clear disruption of smooth pursuit in the patients with minimal hepatic encephalopathy, and more pronounced disruption, if not complete loss, of smooth pursuit in patients with overt hepatic encephalopathy. The differences observed in quantifiable SPEM indices between the healthy volunteers/unimpaired patients and those with overt hepatic encephalopathy were significant (P < .05). In conclusion, SPEM performance is impaired in patients with hepatic encephalopathy in parallel with the degree of neuropsychiatric disturbance: the pathophysiology of these changes is unknown, but retinal, extrapyramidal, and attentional abnormalities are likely to play a role. Treatment status confounds the classification of neuropsychiatric status and should be taken into account when categorizing these patients.

Attention dysfunction in cirrhotic patients: an inquiry on the role of executive control, attention orienting and focusing

Attention alterations are reported in cirrhotics. Aiming at clarifying attention functioning in cirrhotics, an inquiry on the functioning of the anterior (AAS) and the posterior (PAS) attention system was performed. Thirty-six cirrhotics without overt hepatic encephalopathy (24 with EEG or TMT-A alterations) and 16 matched control subjects were enrolled. The AAS was studied by the Stroop task measuring selective attention control, the PAS was studied by the Posner task and the Focus task measuring automatic covert orienting and visual focusing of attention respectively. Cirrhotics presented a task-dependent psychomotor slowing (Stroop > Posner > Focus) with an increased percentage of errors in the incongruent condition of the Stroop task [F(1, 57) = 4.9, p < 0.03]. Class C patients had both a selective slowing [F(1, 33) = 4.3, p < 0.05] and an increased percentage of errors in the incongruent condition [F(1, 34) = 5.1, p < 0.05] compared to Class A-B patients and controls. The patients with an altered EEG performed the Stroop test significantly slowly than those without EEG alterations [F(1, 41) = 8.9, p < 0.01] and with a clear trend for a higher number of errors in the incongruent condition [F(1, 39) = 3.8, p < 0.06]. In contrast, attention orienting and focusing were maintained. In conclusion, the AAS is more sensitive than the PAS to the early stages of hepatic encephalopathy.

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.

Clinical features and survivial of cirrhotic patients with subclinical cognitive alterations detected by the number connection test and computerized psychometric tests

The prevalence and the clinical implications of subclinical cognitive alterations in cirrhotic patients have not been well defined as yet. Therefore, we performed a study to assess the clinical features and the survival of cirrhotic patients with cognitive alterations detected by the number connection test (NCT) and a set of computerized psychometric tests (Scan, Choice1, and Choice2) measuring the reaction times and the percentage of errors in performing specific tasks. Ninety-four cirrhotic patients (aged 58 +/- 9 years) without overt hepatic encephalopathy and 80 controls (aged 53 +/- 15 years) were consecutively enrolled. The median follow-up in cirrhotic patients was 426 days (lower quartile = 213 days; upper quartile = 718 days). Results of the NCT, Scan test, and Choice2 test were significantly worse in cirrhotic patients, whereas Choice1 did not differ significantly from the controls. In cirrhotic patients, the prevalence of altered psychometric tests was 21% (CI95% = 14%-31%) by NCT, 23% (CI95% =15%-33%) by Scan test, and 20% (CI95% =16%-30%) by Choice2 test. The alterations of NCT, Scan, and Choice2 were found to be related to the severity of liver disease, independently of its etiology. Increased risk of death was found to be associated with altered Scan test (hazard ratio = 2.4; CI95% =1. 1-5.3), or altered Choice2 test (hazard ratio = 2.8; CI95% = 1.2-6. 3). Multivariate regression showed that Scan and Choice2 tests had prognostic value on survival, in addition to Child-Pugh classes in the first year of follow-up.

Visual attention in cirrhotic patients: a study on covert visual attention orienting

Attentional dysfunction, which influences overall cognitive productivity, is not well characterized in cirrhotic patients. The aim of this study was to clarify the features of covert visual attention orienting in cirrhotics without overt hepatic encephalopathy. One hundred consecutive cirrhotic patients and 40 controls were enrolled. Visual covert attention orienting was assessed by the Posner test, which evaluates the effect of a cue on visual reaction times. Patients were characterized by the number connection test (NCT) and electroencephalographic (EEG) spectral analysis. The severity of liver disease was graded using standard laboratory parameters and the Child-Pugh's classification. Fifty-five psychometric and EEG evaluations were performed in the follow-up of 17 patients to assess the relationship between the variations of psychometric and neurophysiological findings. NCT and quantified-EEG parameters (altered in 19% and 40% of cirrhotic patients, respectively) were linked to each other and to the severity of liver disease. The Posner test showed a delay of visual reaction times in class B-C cirrhotic patients. Reaction times were correlated with ammonia and EEG parameters. The effect of the cue was higher in cirrhotic patients than in controls, particularly in the invalid position. This study suggests that cirrhotic patients have a reduced activity rate and reduced capacity to disengage attention previously focused on a cue. Such alterations are linked to NCT and EEG findings.

Study on the Sternberg paradigm in cirrhotic patients without overt hepatic encephalopathy

Memory dysfunction is reported in cirrhotics. The aim of this paper was to increase insight into memory function of cirrhotic patients without overt hepatic encephalopathy. Eighty-six consecutive cirrhotics without overt hepatic encephalopathy (aged 54+/-10 yr., mean+/-s.d.) and 28 controls (52+/-10 yr.) with comparable education level were enrolled. Seventeen patients were class A, 55 class B, 14 class C according to Child-Pugh classification; 29 had alcoholic cirrhosis. The presence of subclinical signs of central nervous system dysfunction were assessed by Number Connection Test (NCT) and quantified EEG analysis. Memory scanning was evaluated by reaction times (RTs) in the Sternberg paradigm. MANOVA analysis showed that RTs were higher (F1,99=11, p<0.01) and time outs (TOs) more frequent (F1,110=10, p<0.01) in cirrhotics than in controls, whereas button press errors (BPEs) did not differ significantly (F1,110=2, p=n.s.). In cirrhotics, an interaction Child-Pugh class x memory set size was found (F2,146=4, p<0.05), showing exceedingly delayed RTs with greater memory set size in class C patients. Patients with altered NCT had significantly prolonged RTs (F1,71=4, p<0.05) and more TOs (F1,82=11, p<0.01) than patients with normal NCT. Cirrhotics with altered EEG had significantly prolonged RTs (F2,70=6, p<0.01). RTs were found to be correlated to alpha relative power (r=-0.4, p<0.01) and theta relative power (r=0.4, p<0.01). In conclusion, cirrhotics without over encephalopathy, but with NCT or EEG alterations, perform a computerized digit recognition task more slowly and with higher TOs than cirrhotic patients with normal NCT or EEG. In severe liver insufficiency (class C cirrhotics) also an impairment of memory scanning was detected. Sternberg test performance correlates with NCT and quantitative EEG parameters.