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.