The contingent negative variation and psychological findings in chronic hepatic encephalopathy.

Early diagnosis of chronic hepatic encephalopathy (CHE) in the latent stage before the appearance of clinical signs, should reduce both morbidity and mortality as deterioration is often preventable by treatment. Since existing diagnostic procedures are inadequate, we have investigated a test in which morphine is used as a provocative agent and any resulting change in cerebral function assessed by measurement of the CNV in conjuction with a psychological trail test. Twenty six patients were studied, 6 of whom had clinically overt CHE. A significant correlation (P less than 0.05) between the change in CNV amplitude with morphine and the initial CNV amplitude, consistent with the theoretical model of Tecce (1972), was found. However, the CNV and trail test results taken as a whole did not allow even those patients with overt CHE to be distinguished and we conclude that it is unlikely that differing degrees of latent CHE could be detected.