Feedback EEG in the detection of subclinical hepatic encephalopathy: a preliminary report

The detection, monitoring, and quantification of subclinical hepatic encephalopathy present difficult problems for the clinician caring for patients with liver disease. Traditionally, pencil and paper tests such as signature-writing have been used at the bed-side to measure early encephalopathy. More recently, the Trail-making test has been employed to detect and quantify encephalopathic changes. While the electroencephalogram has provided information about the extent of clinically-obvious encephalopathy, it has only recently proved useful in the detection of subclinical disease. In these cases, evoked potentials and spectral analysis methods have discriminated between 35 and 62% of patients with subclinical hepatic encephalopathy. The present study used the method of feedback electroencephalography to detect and quantify differences in cortical arousal in 5 cirrhotic patients and 5 normal age-matched controls. Subject were also compared with respect to baseline measures of cortical arousal. Finally, arousal during feedback EEG stimulation was correlated with Trail-making test performance. The data revealed that cirrhotic patients can be discriminated from normal controls by baseline (80% detection) and feedback stimulation conditions (100% detection). In addition, feedback EEG reactivity (cortical arousal) was inversely correlated with Trail-making test performance (-0.86, P less than 0.01). The results indicate that simple features of the conventional EEG can reliably discriminate cirrhotic patients from normals. Clinical application of the feedback method in other metabolic encephalopathies, as well as in hypoaroused states secondary to, for example, narcolepsy, is discussed.