Subcortical impairment in subclinical hepatic encephalopathy

We have used short latency somatosensory evoked potential (SEP) in 108 patients with liver cirrhosis by viral hepatitis to evaluate hepatic encephalopathy. Short-latency SEPs were recorded by the MEM-4104 apparatus (Nihon Kohden Inc., Tokyo) in response to median nerve stimulation. For a precise analysis of the early components, we averaged 1000 responses during a 30-msec period. Early SEP components were prolonged in patients with decompensated, but not in those with compensated, cirrhosis. We also examined the relationship between consciousness level and interpeak latency (IPL) N13-N20 of SEP and between consciousness level and electroencephalograph in 51 patients among 108 patients with liver cirrhosis. The IPL N13-N20 was prolonged in the decompensated stage with normal consciousness, but EEG findings had not deteriorated in this stage. EEG grade became worse in the stage of abnormal consciousness. The prolongation of the IPL N13-N20 was attributed to the central conduction impairment. We postulate that subcortical impairment may occur in patients with subclinical hepatic encephalopathy. when the cortex is little affected.