The use of the visual evoked potential (VEP) in delineating a state of subclinical encephalopathy. A comparison with the number connection test (NCT)

Safety profile of sedative endoscopy including cognitive performance in liver cirrhosis: A double-blind randomized controlled trial

The indiscriminate use of sedative drugs during endoscopy can pose multiple risks including cognitive impairment in advanced liver cirrhosis. However, the data are scarce regarding which sedative drugs are safest in these populations. The aim of this study was to evaluate the safety profiles including cognitive performance among midazolam, propofol, and combination therapy in advanced cirrhotic patients. This double-blind randomized controlled study included 60 consecutive advanced cirrhotic patients who underwent upper gastrointestinal endoscopy. The Stroop application was used to screen for cognitive impairment. Patients were randomly assigned to one of 3 groups, midazolam, propofol, or the combination group, and underwent Stroop test before and two hours after the completion of endoscopy. Hemodynamic safety and the subjective satisfaction score were also evaluated. Patients did not show significant changes in on-time or off-time on the Stroop test before and two hours after sedatives, and there was no significant difference among the 3 treatment groups. Also, there were no significant vital sign changes after sedatives. Time-to-recovery was longest in midazolam group, and patient awakening and patient memory were highest in propofol group. However, all 3 groups showed no difference in patient satisfaction, but the combination group was more preferred in terms of subjective satisfaction by physicians. Factors affecting worsened Stroop speed after sedatives were older age, low education level and high MELD score. All sedative methods using midazolam, propofol, or combination therapy showed similar safety profile in advanced cirrhosis, and were not associated with increased risk of cognitive impairment.

Normalization of the psychometric hepatic encephalopathy score in Polish population. A prospective, quantified electroencephalography study

BACKGROUND

The psychometric hepatic encephalopathy score (PHES) is recommended as a gold standard in evaluation of minimal hepatic encephalopathy (HE). Normative databases have been collected in few countries, clearly showing differences among studied groups. Thus, the standardization of PHES for selected populations remains necessary.

AIMS

To standardize PHES in a large cohort of Polish healthy subjects and to evaluate the normograms in patients with cirrhosis with quantified electroencephalography (EEG).

METHODS

Three hundred and sixteen (142 males/174 females, aged 44.5 ± 12.1) normal individuals and 50 (31 males/19 females, aged 52.8 ± 12.4) patients with cirrhosis without overt HE were included. Key correction variables of psychometric tests were performed. The multivariate linear regression was used to calculate PHES normograms.

RESULTS

Age and education levels were identified as predictors of all tests, therefore age- and education-adjusted normograms were developed. A weighted time-errors regression model for line tracing test (LTT) scoring was used. The PHES ranged between +5 and -15 points and the cut-off between normal and pathological PHES was set on ≤-5 points. By this cut-off level, PHES had a sensitivity of 57% and specificity of 97% to diagnose minimal HE (AUC = 0.866 ± 0.028). In patients with cirrhosis, PHES correlated with severity of liver disease (MELD, r = -0.475, P < 0.001 and Child-Pugh classification, r = -0.452, P < 0.002) and EEG (r = 0.547, P < 0.002). In patients with impaired EEG, PHES was lower than in individuals with unaltered EEG (P < 0.02); however, agreement between these two modalities was limited.

CONCLUSIONS

Valid Polish PHES normograms, which incorporates w-LTT scoring system have been developed. Future multi-centre international studies are needed to validate widely applicable norms.

Minimal hepatic encephalopathy does not impair health-related quality of life in patients with cirrhosis: a prospective study

BACKGROUND

Minimal hepatic encephalopathy (HE) is a serious complication of cirrhosis; however, the impact of minimal HE on health-related quality of life (HRQoL) remains controversial. The Psychometric Hepatic Encephalopathy Score (PHES) remains a 'gold standard' for the assessment of minimal HE, but its results clearly differ between studied populations.

AIM

We studied the effect of minimal HE on patient HRQoL.

METHODS

Eighty-seven consecutive cirrhotic patients were included. All patients underwent clinical and psychometric evaluation at the same day. Ten subjects with overt HE confirmed with West Haven criteria were excluded from the study, thus 77 patients were finally analysed. Patients with minimal HE were identified on the grounds of altered PHES. HRQoL was assessed by the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36) and the Chronic Liver Disease Questionnaire (CLDQ). Normative reference data for PHES were established from a cohort of 305 healthy Polish subjects.

RESULTS

Twenty-nine (37.7%) patients were diagnosed with minimal HE. When patients with and without minimal HE were compared, HRQoL was not significantly different in none of the SF-36 and CLDQ domains.

CONCLUSION

Minimal HE does not affect HRQoL.

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.

Electrophysiological and neuropsychological tests for the diagnosis of subclinical hepatic encephalopathy and prediction of overt encephalopathy

BACKGROUND

Subclinical hepatic encephalopathy (SHE) features in 30-84% of patients with cirrhosis of the liver. Its clinical significance with regards to progression to overt encephalopathy has however, not been established.

AIMS

The present study was conducted (i) to compare the diagnostic usefulness of neuropsychological tests with that of electrophysiological (EP) tests in detection of SHE, and (ii) to examine the natural course of SHE.

METHODS

Seventy-five-nonencephalopathic cirrhotics (11 females, 64 males; mean (+/- SD) age 43.6 (+/- 11.7) years; mean (+/- SD) education 11(+/- 3) years) were studied using a battery of tests for intelligence and memory, the number connection test (NCT), and EP tests viz. electroencephalogram (EEG) and auditory P300 event related potentials (P3ERP). All the patients were followed up for a period of 6 months to 2 years for development of overt encephalopathy.

RESULTS

Thirty-five out of 75(47%) patients were diagnosed to have SHE based on at least one abnormal test result. The P3ERP latencies detected SHE in maximum number of patients (23%) followed by EEG (21%). Nearly 59% of patients with SHE progressed to overt encephalopathy within a mean duration of 4 months. Multivariate analysis showed that prior episode of encephalopathy (RR = 6.3; 95% CI = 2.0-19.7), abnormality on EEG (RR = 7.5; 95% CI = 2.2-25.3), abnormal performance on psychometric battery of tests (RR = 35.2; 95% CI = 4.3-287.3), occurrence of gastrointestinal bleed (RR = 19.3; 95% CI = 4.1-88.9), occurrence of dehydration (RR = 10.7; 95% CI = 2.5-45.4) and infection (RR = 11.4; 95% CI = 2.0-64.4) had significantly higher risk for development of overt encephalopathy.

CONCLUSIONS

EP methods were more sensitive in detection of SHE. Amongst all the tests used, presence of only an abnormal EEG was significantly associated with development of overt encephalopathy along with the precipitating factors.

Auditory P300 event-related potentials and number connection test for evaluation of subclinical hepatic encephalopathy in patients with cirrhosis of the liver: a follow-up study

BACKGROUND AND AIMS

The P300 event-related potentials (P3ERP) have been recently advocated for detection of cognitive disturbances in early encephalopathy. However, no systematic follow-up study has been conducted to understand the clinical significance of subclinical hepatic encephalopathy (SHE) detected by this or other methods. The present study was therefore undertaken to examine the diagnostic usefulness of auditory P3ERP in the detection of SHE, to compare it with that of the number connection test (NCT), and to investigate the clinical outcome of patients with SHE in terms of progression to overt encephalopathy.

METHODS

P300 event-related potential latencies were measured and the NCT time was recorded in 81 non-encephalopathic cirrhotic patients (Aged 43.8 +/- 11 years, 23 alcoholic and 58 non-alcoholics) attending the outpatient department at our tertiary care hospital (All India Institute of Medical Sciences Hospital). Cut-off values for abnormality in the tests were developed from age-, sex- and education-matched controls. Patients were followed up at regular intervals for the development of overt encephalopathy, and the identifiable precipitating factors were noted. The P3ERP latencies (363 +/- 34 msec vs 349 +/- 23 msec), as well as NCT time (54.6 +/- 30.6 s vs 39.5 +/- 15.8 s) were significantly prolonged (P< 0.01) in patients with liver cirrhosis when compared with the non-cirrhotic controls.

RESULTS

The P3ERP defects were seen in 24.6% of cirrhotic patients, while NCT time was prolonged in 19.7% of the patients. Nearly 43% of the patients with SHE progressed to overt encephalopathy within a mean duration of 5 months, while only 3.9% of the non-SHE patients did so. Of the patients who developed overt encephalopathy, 64.2% had P3ERP latency prolongations while 35.7% had abnormal NCT.

CONCLUSIONS

The results of the present study suggest that P3ERP and NCT are valid tools for the screening of SHE in cirrhotic patients as there is a greater likelihood of overt encephalopathy development in patients with an abnormality detected by these tests than in patients with no such abnormality.

Visual event-related potentials in cirrhotic patients without overt encephalopathy

Ambulant patients with cirrhosis and no clinical evidence of encephalopathy were screened for impaired brain function by neuroelectrophysiological testing dependent on cognitive function. Infrequent large checkerboard visual stimuli were randomly interleaved with frequent small ones to elicit P300 event-related potentials (ERPs). Three ERP components, N200, P3a and P3b, were derived from the electroencephalogram (EEG) by computer averaging. The use of 10% contrast and a minimum of four precisely placed scalp electrodes were found to be necessary for optimal separation of ERPs from sensory evoked potentials. Visual ERPs, onset/offset and pattern-reversal visual evoked potentials (VEPs), the spontaneous EEG and the time taken to complete a standard number connection test (NCT) were obtained from 20 normal adult subjects and 19 age-matched patients with histologically-confirmed cirrhosis and no clinical evidence encephalopathy. The latencies and amplitudes of evoked potentials and the alpha rhythm of the EEG were determined. In 6 of the 19 patients the latencies of P3a and/or P3b exceeded the corresponding mean for controls + 2 standard deviations of that mean. In 4 other patients the NCT was prolonged. In all of the patients the N200, VEPs and alpha rhythm of the EEG were normal.

IN CONCLUSION

(i) Optimal isolation of ERPs is critically dependent on stimulus contrast and electrode placement; (ii) ERPs appear to be more sensitive than primary sensory evoked potentials or the EEG in detecting impaired brain neuroelectrophysiological function; and (iii) Cirrhotic patients without overt encephalopathy in whom P3a and/or P3b latencies are prolonged may have subclinical hepatic encephalopathy.

Spectral versus visual EEG analysis in mild hepatic encephalopathy

OBJECTIVE

Spectral EEG analysis has been claimed to reduce subjective variability in EEG assessment of hepatic encephalopathy and to allow the detection of mild encephalopathy.

METHOD

To test such assumptions, 43 digital EEG were recorded in 32 cirrhotics without overt encephalopathy or with grade 1 overt encephalopathy; 7 patients were re-tested (2-5 times) in their follow up. All patients underwent psychometric assessment. Nineteen controls were considered. EEG were blindly evaluated by two electroencephalographers and by spectral EEG analysis performed according to 3 different techniques.

RESULTS

The reliability of the classification based on spectral analysis (biparietal technique) was higher than that based on a three-degree qualitative visual reading (concordance/discordance = 58/4 versus 46/16 P < 0.01) and comparable with that of semiquantitative visual assessment based on posterior basic rhythm (concordance/discordance = 55/7 P = 0.5). The accuracy of spectral EEG analysis was higher than that of qualitative visual EEG readings alone (90 versus 75%) and comparable to semi-quantitative visual assessment (87%), however, statistical significance was not reached. In the follow-up, the variations of theta and delta relative power were found to be significantly correlated with psychometric variations.

CONCLUSIONS

In conclusion, spectral EEG analysis may improve the assessment of mild hepatic encephalopathy by decreasing inter-operator variability and providing reliable parameters correlated with mental status.

Risk of sedation for upper GI endoscopy exacerbating subclinical hepatic encephalopathy in patients with cirrhosis

BACKGROUND

The risk of exacerbating subclinical hepatic encephalopathy associated with the administration of sedative drugs in patients with cirrhosis undergoing diagnostic upper gastrointestinal (GI) endoscopy for portal hypertension remains to be determined.

METHODS

Ten adult patients with cirrhosis completed number connection tests before sedation for endoscopy and at discharge from the endoscopy unit 2 hours post-procedure. Control patients consisted of five patients with cirrhosis undergoing the same procedure for the same indication who did not receive sedation and 12 patients with no evidence of liver disease who received sedation before diagnostic endoscopy for a variety of GI complaints. The control populations were age, gender, education level, and, in the case of patients with cirrhosis, Child Pugh s score matched to the patients with cirrhosis who received sedation.

RESULTS

The mean (+/- SEM) age of patients with cirrhosis who received sedation was 59.6 +/- 3.8 years. Seven of the ten (70%) were men. Their mean Child Pugh s score was 7.2 +/- 1.5. Nine of the ten (90%) had abnormal baseline number connection tests results (mean for the group 52.3 +/- 6.7 seconds) the extent of which correlated with Child Pugh s scores (p < 0.005). Individually, the baseline number connection tests results were normal in one (10%), mild in six (60%), moderate in one (10%), and severe in two (20%). After the procedure (before discharge) the mean number connection tests result was 61.5 +/- 7.9 seconds (p = 0.01 when compared with baseline). The results were now normal in none (0%), mild in four (40%), moderate in four (40%), and severe in two (20%). Pre- and post-procedure number connection tests results did not change in the non-sedated cirrhotic or sedated non-liver disease control patients.

CONCLUSIONS

The results of this study indicate that (1) the majority of patients with cirrhosis and suspected portal hypertension have evidence of subclinical hepatic encephalopathy, (2) the extent of encephalopathy correlates with the Child Pugh's score, (3) sedation with midazolam for upper GI endoscopy exacerbates the encephalopathy, and (4) this adverse effect is still evident 2 hours after the procedure.

Neurovisual impairment: a frequent complication of alpha-interferon treatment in chronic viral hepatitis

Following our earlier observation of clinically evident optic tract neuropathy in patients receiving low-dose interferon (IFN) therapy, we prospectively evaluated 53 consecutive patients treated for chronic hepatitis B or C with a median dose of 3 MU of IFN-a2b thrice weekly. Measurements included routine ophthalmologic evaluation and recordings of visual evoked responses (VER), electroretinograms (ERG), visual acuity, and visual fields, before, at the end of IFN treatment, and at follow-up visits. Baseline P100 latencies of VERs (base-VER) were abnormally prolonged in 24 patients (32 of 106 eyes, 30.2%); age was the only significant covariate associated with increased risk for an abnormal base-VER by multiple logistic regression (relative risk [RR] 5.3 per each 5-year increase in age). In 45 patients (74 eyes) with normal baseline P100 latencies, the end-of-treatment VERs (end-VER) were significantly prolonged compared with baseline, becoming abnormal in 11 (15 of 74 eyes, 20.3%) (138.8+/-8.7 vs. 117.7+/-5.2 ms, P < .001). This subgroup had older age (59.1+/-11.0 vs. 47.5+/-15.3, P=.007) and reduced visual sensitivity compared with their own pretreatment measurements (24.5+/-1.6 vs. 23.0+/-1.2db, P=.019). Changes of end-VERs by age had a sigmoid distribution with a steep increase of values beyond the 5th decade (R2=.326, P < .001). In a logistic regression model, significant predictors of abnormal end-VERs were, patients' age (RR 5.6 per each 5-year increase), presence of hepatitis B virus (HBV) infection (RR 15.1 compared with hepatitis C virus [HCV] infection) and serum cholesterol levels above 240 mg% (RR 7.1 compared with values < 240 mg%). Subconjunctival hemorrhages were seen in 2 cases and funduscopic examination revealed cotton wool spots in one other. ERG recordings and the P100 amplitude remained unchanged. After stopping IFN, the treatment-associated neurovisual abnormalities reversed to normal in 7 patients (10 of 15 eyes) and persisted in 5 (5 of 15 eyes, 33.3%) for up to 37 (median 7.3) months observation, all patients remaining clinically asymptomatic. In conclusion, subclinical neurovisual impairment is a frequent, largely unrecognized complication of low-dose IFN therapy, and patients with chronic hepatitis B and older age appear to be most susceptible. This apparently innocuous complication is long lasting, possibly irreversible in some patients, with yet undetermined consequences on visual function.

Visual and auditory evoked responses in acute severe hepatitis

Evoked responses have not been studied in patients with acute severe hepatitis (ASH) with or without hepatic encephalopathy. This prospective study was undertaken to find out diagnostic as well as prognostic value of visual evoked responses (VER), and brain stem auditory evoked responses (BAER) in patients with ASH with or without encephalopathy. Visual evoked responses and BAER were studied in 20 patients (14 males and six females) with ASH. The patients were diagnosed as having severe hepatitis if acute hepatitis was associated with raised serum bilirubin and serum transaminases, and if they had a prothrombin time index of < 50%. After a detailed neuropsychiatric examination of each patient, the study sample was divided into two groups of 10 patients: ASH without encephalopathy (ASH-WOE), and ASH with encephalopathy (fulminant hepatic failure, FHF). The median P100 latencies of FHF patients were significantly increased compared with controls and patients in the ASH-WOE group. Abnormal P100 latencies, exceeding 95th percentile values of the controls, were present in one patient in the ASH-WOE group and six patients in the FHF group. The median interpeak latencies I-III, III-V and I-V were significantly prolonged in the FHF group. Interpeak latencies III-V were also increased significantly in patients in the ASH-WOE group. While abnormal BAER were seen frequently in both groups, VER abnormalities were largely confined to patients in the FHF group. In the FHF group, six out of 10 patients survived and exhibited clinical improvement in the status of hepatic encephalopathy. Evoked responses were repeated after 2-3 weeks of recovery in these patients and VER abnormalities showed a tendency to normalize, thereby suggesting a prognostic implication. The incidence of abnormal VER in hepatic encephalopathy complicating ASH far exceeded that of abnormal BAER. Markedly prolonged P100 latencies in FHF patients indicate poor prognosis.

Dynamics of cognitive brain dysfunction in patients with cirrhotic liver disease: an event-related P300 potential perspective

The dynamics of cognitive brain functions of 104 patients with both chronic non-cirrhotic (NC) and cirrhotic liver disease (C: C1, non-encephalopathic; C2, encephalopathic) were investigated by means of visual P300 potentials elicited in both the paradigms of transient (PI) and selective attention (PII). Conventional PVEPs, psychometric tests and quantitative liver function tests were also performed. As compared to both an age-matched control group (N) and the non-cirrhotic patients (NC), the N250 and P300 latencies of the cirrhotics (C) were equally prolonged in both P300 paradigms (P = 0.0001). By contrast, the P300 amplitudes were not different between the patient groups in either P300 paradigm. In the cirrhotics, however, the P300 amplitude differences between PII and PI (+ 3.7 +/- 2.8 muV, mean +/- 1 S.D.) were significantly (P < 0.01) smaller than in the non-cirrhotics (+ 7.5 +/- 5.2 muV) reflecting disturbances in the dynamics of visual attention. Interestingly, these P300 amplitude differences between both paradigms were positively correlated (r = 0.35; P = 0.005) with hepatic metabolic capacity, but not with liver blood flow (r = 0.23; P > 0.05). The diagnostic efficacy of the visual P300 in PI (sensitivity, 48%; specificity, 100%) was lower than that of the visual P300 in PII (79%; 100%) and that of the psychometric tests (63%; 94%), but it remained superior to that of the PVEPs (29%; 97%). It is concluded that in patients with cirrhotic liver disease visual P300 potentials can even reveal the dynamics of minor cognitive brain dysfunction and may also provide interesting pathophysiological information.

Subcortical somatosensory evoked potentials in patients with hepatic encephalopathy caused by severe acute hepatitis

We studied the median nerve stimulated somatosensory evoked potentials (SEP) of 23 patients with hepatic encephalopathy (HE) resulting from severe acute hepatitis and 22 healthy volunteers. Ten patients who improved and survived more than 60 days were classified as Group 1 and the remaining 13 patients who died shortly after the SEP studies were classified as Group 2. The mean N9-N13 interpeak latencies (IPL) were not different among control and two patient groups. The mean N13-N20 IPL of Group 2 was significantly prolonged when compared with normal controls (P < 0.001) and Group 1 (P < 0.001). Five of the six patients with abnormal N13-N20 IPL died of hepatic failure within 24 h after SEP testing. The occurrence of abnormal subcortical conduction together with cortical dysfunction suggested that brain damage in terminal hepatic encephalopathy was diffuse. The presentation of abnormal prolongation of N13-N20 IPL of SEP during the course of severe acute hepatitis indicated a poor prognosis. Peripheral somatosensory conduction is unaffected even in terminal HE.

Cerebral function analyzing monitor and visual evoked potentials as a noninvasive method of detecting cerebral dysfunction in patients with acute hepatic and renal failure treated with intermittent machine hemofiltration

We monitored the effect of 7 intermittent machine hemofiltration treatments in 4 patients with fulminant hepatic failure who had progressed to grade IV coma and developed acute oliguric renal failure. Prior to treatment the processed EEG showed excess slow wave activity, and the latency of the later visual evoked potentials (N2 and P2) was delayed. Following treatment there was a further increase in both EEG slow wave activity and latency of the N1, N2, and P2 potentials. Intracranial pressure increased from a median of 8 mm Hg (2-12, range) to 14 (8-28) following treatment, p < 0.05. There was a correlation between intracranial pressure and all of the later visual evoked potentials, for N3 r = 0.71, for P1 r = 0.39, and P2 r = 0.74, all p < 0.05. Although there appeared to be a good correlation between intracranial pressure and the noninvasive electrophysiological recordings, there were major changes in intracranial pressure, cerebral perfusion pressure, and cerebrospinal fluid pH during the first hour of treatment, during which time there were no discernable changes in EEG or evoked potentials. In this study, non-invasive neurophysiological methods were not found to be reliable as invasive methods in assessing acute, minute-by-minute changes in cerebral metabolism but these methods may have a role in the longer term in assessing patient prognosis.

Visual event-related P300 potentials in early portosystemic encephalopathy

Visual event-related P300 potentials, conventional visual evoked potentials, and psychometric tests were applied to patients with noncirrhotic chronic liver disease and to clinically nonencephalopathic and encephalopathic cirrhotics to compare their diagnostic efficacy in detecting early portosystemic encephalopathy (PSE). Sixty-four investigations were performed in 58 patients. The latencies of the P300 parameters were significantly longer in both the encephalopathic and nonencephalopathic cirrhotics than in the noncirrhotics, indicating distinctly abnormal cortical processing of visual stimuli in cirrhotic patients. The visual P300 potentials showed the highest sensitivity and specificity for grade I PSE. Abnormal P300 test results were also found in 78% of the clinically nonencephalopathic cirrhotics, while psychometric tests showed abnormalities in only 41%. The P300 latencies were similar in alcoholic and nonalcoholic cirrhotics. Significant inverse correlations were found between the P300 latencies and measures of quantitative liver function such as galactose-elimination capacity and aminopyrine breath test. It is concluded that visual event-related P300 potentials are a sensitive index of subclinical and grade I PSE. Furthermore, the degree of cognitive dysfunction detected by this method in patients with liver cirrhosis appears to be related to the reduction in hepatic metabolic capacity.

EEG and event related potentials in hepatic encephalopathy

In recent years, there have been considerable developments in the application of EEG and event related potential technology to the diagnosis and assessment of hepatic encephalopathy in cirrhotic patients. A review of the literature on this subject is reported. The visually interpreted EEG is only of benefit in the late stages of hepatic encephalopathy. EEG spectral analysis allows identification of all stages of the condition. Brainstem auditory evoked responses are normal in encephalopathy. Visual evoked responses show an increase in the latency and eventual loss of individual component waves as encephalopathy progresses. Somatosensory evoked responses show a progressive prolongation of peak and inter-peak latency which correlates with the severity of encephalopathy. The auditory P300 evoked response shows an increased latency with the development of hepatic encephalopathy. Event related potentials provide objective diagnostic markers of the development of hepatic encephalopathy. The increased use of this technology in the assessment of patients with this condition should be of clinical benefit in its management.

Flash visual evoked responses in the early encephalopathy of chronic liver disease

In recent years many variants of EEG sensory evoked responses have been studied as potential diagnostic aids in the detection and quantification of hepatic encephalopathy (HE). This study assesses the value of the flash visual evoked response (VER). Twenty-six controls and 21 non-encephalopathic and 12 encephalopathic (grade 1/2), biopsy-proven, cirrhotic patients were assessed clinically, psychometrically, and electrophysiologically. Flash VER from three different leads were obtained from each patient. Data from the fronto-occipital leads gave the best differentiation between the subjects. The P2 and N3 peak latencies were significantly increased in the two liver groups and correlated with the mental state and psychometric results. The N3 latency had a 92% specificity and a 50% sensitivity in the detection of grade 1/2 HE. This study suggests that the N3 latency changes may be a good marker of early clinical HE and useful in the longitudinal assessment of individual patients.

Visual evoked potential--a tool in the diagnosis of hepatic encephalopathy?

Visual evoked potentials (VEP) have been suggested to be of value in the diagnosis of subclinical and mild hepatic encephalopathy. In the present study, a comparison between VEP and four psychometric tests (number connection test A and B, digit symbol and word memory test) was performed in 42 cirrhotic patients, 17 of whom had clinical signs of encephalopathy. The results were compared to sex- and age-matched healthy controls. The VEP latencies for P2 (the second positive wave) and N3 (the third negative wave) were 11% and 26% longer (P less than 0.01-0.001) in the patients than in the controls. Moreover, the latencies for N2 (the second negative wave) and P2 were longer in the encephalopathic as compared to the non-encephalopathic patients (P less than 0.05). There was a significant correlation between the latencies for N2 and number connection tests A and B and digit symbol test. However, of the patients with clinical encephalopathy, less than half had VEP latencies longer than the mean +/- 2 S.D. above those for the controls. In contrast, none of the encephalopathic patients had normal results on the psychometric tests. This study demonstrates that although statistically significant differences exist between groups of cirrhotic patients and controls, VEP is not a reliable tool for the diagnosis of encephalopathy in the individual patient.