Raffaele Orsato

University of Verona, Verona, Veneto, Italy

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Publications (7)26.55 Total impact

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    ABSTRACT: Electroencephalography has not been completely quantified in patients with cirrhosis. We investigated the electroencephalogram (EEG) dynamics in patients with cirrhosis. We performed closed-eye EEGs on 175 patients with cirrhosis (age, 55 ± 11 years; 24% Child-Pugh class A, 48% class B, and 285 class C), conducted clinical and psychometric assessments for hepatic encephalopathy (HE), and followed the patients for 1 year. EEG characteristics were assessed in the frequency domain, in the frontal (F3-F4) and parietal (P3-P4) derivations. Intrahemispheric (frontoparietal, right, and left) and interhemispheric (F3-F4 and P3-P4) coherence were computed. The EEGs of 50 healthy volunteers (age, 56 ± 17 years) served as controls. Compared with controls, the EEGs of patients with cirrhosis had a reduced frequency in the posterior derivations (P3/P4 mean dominant frequency, 9.1 ± 1.8 and 8.9 ± 1.7 Hz vs 10.4 ± 1.3 and 10.2 ± 1.3 Hz, respectively; P < .01) and an increase in interhemispheric parietal relative coherence within the theta band (22.3% ± 5.5% vs 18.9% ± 3.5%; P < .01). These features were more prominent in patients with Child class C and in patients with a history of overt HE; they correlated with hyperammonemia and hyponatremia. The decrease in EEG frequency, along with the increase in interhemispheric theta coherence in the posterior derivations, was inversely associated with survival and the occurrence of overt HE during the follow-up period. In patients with cirrhosis, alterations in the EEG were significantly associated with the severity of liver disease and HE; the EEG might be used in determining prognosis.
    Gastroenterology 07/2011; 141(5):1680-9.e1-2. · 12.82 Impact Factor
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    ABSTRACT: To compare electroencephalographic spectral analysis obtained by periodogram (calculated by means of Fast Fourier Transform) and autoregressive (AR) modelling for the assessment of hepatic encephalopathy. The mean dominant frequency (MDF) and the relative power of delta, theta, alpha, and beta bands were computed by both techniques from the electroencephalograms (EEG) of 201 cirrhotics and were evaluated in the clinical and prognostic assessment of the patients. The values of all the five indexes computed by periodogram and AR modelling matched each other, but the latter provided stable values after the analysis of fewer epochs. Independently of the technique, the relative power of theta and alpha bands fitted the clinical data and had prognostic value. The relative power of beta and delta bands computed by AR modelling fitted more closely with clinical data fitted the clinical data more closely. The electroencephalographic spectral indexes obtained by periodogram and AR modelling were found to be, on average, undistinguishable, but the latter appeared less sensitive to noise and provided a more reliable assessment of low-power bands.
    Neurophysiologie Clinique/Clinical Neurophysiology 05/2009; 39(2):107-15. · 2.55 Impact Factor
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    ABSTRACT: The EEG provides an objective staging of hepatic encephalopathy (HE), but its interpretation may be biased by inter-observer variability. This study aims at comparing an entirely automatic EEG classification of HE based on an artificial neural network-expert system procedure (ANNES) with visual and spectral analysis based EEG classifications. Two hundred and thirty-eight consecutive cirrhotic patients underwent closed-eye EEG. They were followed up for up to one-year to detect bouts of overt HE and death. The EEG was classified by ANNES, qualitative visual reading, main basic rhythm frequency and spectral analysis. The classifications were assessed on the basis of: (i) match with liver function, (ii) prognostic value and (iii) repeatability. All classifications were found to be related to the severity of liver failure, with cognitive findings and a history of previous bouts of HE. All of them had prognostic value on the occurrence of overt HE and on survival. The ANNES based classification was more repeatable than the qualitative visual one, and had the advantage of detecting low power EEG, but its efficiency in analyzing low-grade alterations was questionable. An entirely automatic - ANNES based - EEG classification of HE can improve the repeatability of EEG assessment, but further improvement of the device is required to classify mild alterations. The ANNES based EEG grading of HE needs further improvements to be recommended in clinical practice, but it is already sufficient for detecting normal and clearly altered EEG tracings.
    Clinical Neurophysiology 11/2006; 117(10):2243-51. · 3.14 Impact Factor
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    ABSTRACT: 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). 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. 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. In the extrastriate cortex of cirrhotic patients without HE, top-down processes are altered whereas bottom-up processes are preserved. 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.
    Clinical Neurophysiology 09/2006; 117(8):1728-36. · 3.14 Impact Factor
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    ABSTRACT: Abnormality in movement initiation may partially explain psychomotor delay of cirrhotic patients, even in the absence of overt hepatic encephalopathy (HE). Therefore, the aim of this study was to determine the mechanisms of psychomotor delay observed in patients with cirrhosis in the absence of overt HE. Fourteen patients with nonalcoholic cirrhosis and 12 healthy matched control subjects underwent the lateralized readiness potential (LRP) measurement elicited by a visuospatial compatibility task (Simon task). Stimulus-triggered LRPonset reflects the time in which response is selected, while response-triggered LRP onset reflects motor execution. Cirrhotic patients showed delayed reaction times (RTs) compared to controls, particularly those with trial-making test A (TMT-A) or electroencephalogram (EEG) alterations. Stimulus-triggered LRP onset was found to be delayed in cirrhotic patients compared to controls, with a significant Group-versus-Condition interaction, showing a reduced cognitive ability to cope with interfering codes, even in patients without minimal HE (MHE). Response-triggered LRP was found to be delayed only in the patients with TMT-A or EEG alterations. In conclusion, cirrhotic patients without overt HE display a psychomotor slowing, depending first lyon response inhibition and only later accompanied by impaired motor execution.
    Metabolic Brain Disease 01/2006; 20(4):381-92. · 2.33 Impact Factor
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    ABSTRACT: To provide an objective EEG assessment of hepatic encephalopathy (HE), we set up and tested an entirely automatic procedure based on an artificial neural network-expert system software (ANNESS). A training set sample of 50 EEG (group A) and a test sample of 50 EEG (group B) of 100 cirrhotic patients were considered. The EEGs had been visually classified by an expert electroencephalographer, using a modified five-degree Parsons-Simith classification of HE. The efficiency of the ANNESS, trained in group A, was tested in group B. Both the ANNESS and the visually-based classifications were found to be correlated to liver insufficiency, as assessed by the Child-Pugh score (Spearman's coefficient rho=0.485, P<0.0001; rho=0.489, P<0.0001, respectively) and by the biochemical indexes of hepatic function (bilirubin: rho=0.31 vs. 0.27; albumin: rho=-0.13 vs. -0.18; prothrombin time rho=-0.35 vs. -0.52). The classifications were found to be correlated to each other (rho=0.84 P<0.0001, Cohen's kappa=0.55). However, the ANNESS overestimated grade 2 EEG alterations. An ANNESS-based classification of EEG in HE provided data comparable with a visually-based classification, except for mild alterations (class 2) that tended to be overestimated. Further optimization of automatic EEG staging of HE is desirable, as well as a prospective clinical evaluation.
    Neurophysiologie Clinique/Clinical Neurophysiology 01/2005; 35(5-6):162-7. · 2.55 Impact Factor
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    Journal of Hepatology - J HEPATOL. 01/2004; 40:72-72.