Prevalence and prognostic value of quantified electroencephalogram (EEG) alterations in cirrhotic patients

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Abstract

Background/Aims: The electroencephalogram (EEG) is frequently altered in cirrhotic patients. We, therefore, performed a study to ascertain the features and the prognosis of cirrhotic patients without current overt hepatic encephalopathy (OHE) who have EEG alterations.

Methods: A series of 296 consecutive cirrhotic patients who had undergone quantified-EEG was studied. The median follow-up was 442 days, 128 patients had bouts of OHE and 78 patients died from liver-related causes. Another group of 124 cirrhotic patients with a median follow-up of 223 days was examined to validate the prognostic model.

Results: EEG alterations were detected in 38% of the patients. The prevalence of EEG alterations was associated with the severity of cirrhosis (class B: odds ratio (OR)=2.3, 95% confidence interval (CI)=1.2–4.7; class C: OR=3.5, 95% CI=1.6–7.7), but not with the aetiology (alcoholic vs. non-alcoholic: OR=0.9; 95% CI=0.5–1.5). The EEG predicted the occurrence of OHE (χ2=26; P<0.001) and mortality (χ2=34; P<0.001), also adjusting for Child–Pugh class by a multivariate analysis. In the patients with a Child–Pugh score of 8, the EEG discriminated between those patients with a higher 1-year risk of OHE (hazard ratio (HR)=3.3, 95% CI=1.8–6.1) and death (HR=3.1, 95% CI=1.7–5.6).

Conclusions: In conclusion, quantified-EEG had a prognostic value for the occurrence of bouts of OHE and mortality in cirrhotic patients.

Introduction

Abnormalities of the electroencephalogram (EEG) in hepatic encephalopathy have been known since 1950 when Foley et al. [1] described the slow high-voltage EEG discharges in patients with hepatic coma. The visual EEG findings in cirrhosis and their relationship to mental and neurological conditions were clearly described by Parsons-Smith et al. [2]. An objective classification of EEG alterations in hepatic encephalopathy that was based on EEG parameters obtained by automatic quantitative spectral analysis was proposed more recently by Van der Rijt et al. [3]. Such a technique increases the reliability of EEG assessment [4]. Even though Van der Rijt et al. [3] had not specifically addressed their research to the diagnosis of subclinical encephalopathy, subsequent studies [5], [6], [7], [8] showed that about 19–33% of cirrhotic patients without present overt hepatic encephalopathy (OHE) have EEG alterations according to Van der Rijt et al. criteria [3]. Moreover, the cirrhotic patients with such alterations were found to have an increased risk of both neuropsychological impairment [6], [7] and a reduced quality of life [9]. The existence of quantified-EEG alterations were found to have an ominous prognostic value on survival in a small study by Van der Rijt and Schalm [10]. However, a recent paper by Hartmann et al. [11] showed a poor prognostic value of subclinical hepatic encephalopathy defined as the presence of EEG or psychometric alteration in a series of cirrhotic out-patients with predominantly mild liver disease.

We, therefore, performed a study aimed at assessing the prevalence of EEG abnormalities in cirrhotic patients without OHE, and the clinical outcome of the patients with EEG abnormalities.

Section snippets

Patients

Cirrhotic patients without present OHE whose conditions were stable and who consecutively underwent quantified-EEG in our unit (a routine examination in our centre) were considered for the study. OHE was defined as encephalopathy clearly exceeding grade 1 according to Conn's criteria [12], and therefore requiring hospitalization. The patients recruited had normal orientation (personal identity, present situation, place and time) and were ambulant; however, patients with minor signs of

Results

The main demographic, clinical, biochemical and EEG data of the patients in the study group and the validation group are shown in Table 1. Three patients had had a spleno–renal shunt in both the study and validation groups, whereas no patient had undergone a transjugular intrahepatic portal systemic shunt or other portal–systemic shunt procedures either in the study or validation group.

Discussion

The EEG provides information on metabolic encephalopathies because it reflects neuronal electrogenesis which, in turn, is quite sensitive both to the influence of nutritive and energy-providing metabolic systems, and to the influence of electrolyte homeostasis and of the clearance of toxic substances [14]. However, information regarding the relationship between EEG and liver function in cirrhosis is scanty. Quero et al. [8] showed a trend towards a higher degree of EEG alterations in Child–Pugh

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