Thirty-six patients with advanced chronic liver disease of predominantly alcoholic etiology and with a documented history or current physical evidence of hepatic encephalopathy were studied and compared to 30 healthy controls. Assessment was made of their mental state, number connection test, venous blood ammonia, electroencephalography and visual evoked potentials with both pattern reversal and flash stimuli. Because of considerable inter-and intraindividual variation in waveform, visual evoked potentials from flash stimuli were considered unreliable. In pattern reversal visual evoked potentials, the latency of the N1 and P1 waves was significantly longer (p < 0.05) in patients than in controls; however, the wave latencies did not correlate with the mental state score. The mental state score correlated with the number connection test (r = 0.69, p < 0.001), asterixis (r = 0.36, p < 0.05), electroencephalography mean dominant frequency (r = 0.44, p < 0.01) and blood ammonia (r = 0.60, p < 0.01). In 14 patients studied sequentially, change in the mental state score correlated with change in the number connection test (r = 0.80, p < 0.01) and asterixis (r = 0.75, p < 0.01) but not with change in the electroencephalography, blood ammonia or visual evoked potential wave latencies. Al- though visual evoked potentials are abnormal in patients with alcoholic cirrhosis and encephalopathy, they are less accurate in assessing the level of consciousness than simple bedside evaluation with a number connection test.
Currently clinicians must rely upon neurological assessment, psychometric tests, blood ammonia or electroencephalography (EEG) for the staging of the degree of hepatic encephalopathy. These methods of assessment suffer from being subjective, insensitive or nonspecific (1).
Visual evoked potentials (VEPs) have been used in animals with fulminant hepatic failure (2-5) and also in man with hepatic encephalopathy (6-8). The animal data suggested that the VEP wave pattern could be used not only to gauge the severity of coma, but also to distinguish coma induced by different toxins or drugs. Zeneroli et al. (6) used flash evoked potentials in patients with cirrhosis