Evoked potentials in liver diseases

Abstract

Evoked potentials are objective and quantitative methods capable of evaluating functions of both peripheral and central nervous systems (PNS and CNS). During the past 8 years, we have been using somatosensory, brainstem auditory, and pattern-reversal visual evoked potentials (SEP, BAEP, VEP) to study hepatic encephalopathy (HE) as well as functional status of the PNS and CNS in various liver diseases including viral hepatitis B, alcoholic liver disease and Wilson's disease (WD). In HE irrespective of its etiologies, there is a sequential prolongation and eventual disappearance of cortical components of the median nerve evoked SEP while there is no change in BAEP, suggesting that HE is primarily due to a disturbance in cerebral cortical function and that median SEP may be used for early detection of HE and for monitoring its clinical course. In addition, absence of the N20-P25 component, or presence of only the N20 component of the wave complex in fulminant hepatic failure is associated with high mortality, whereas presence of late cortical components in HE is usually associated with reversibility of clinical course. Central conduction time (CCT) of the BAEP is prolonged in patients with WD, alcoholic liver disease and liver cirrhosis due to hepatitis B. Furthermore, BAEP abnormality is most severe in WD, followed by alcoholic liver disease, and finally hepatitis B. Peripheral nerve conduction as determined by the N9 latency of SEP is slowed in alcoholic liver disease and liver cirrhosis of chronic hepatitis B, but normal in WD. Our studies, therefore, suggest that evoked potentials may be useful in the evaluation of both CNS and PNS functions in various liver diseases and also in the diagnosis and monitoring of HE.