Electrophysiological and neuropsychological tests for the diagnosis of subclinical hepatic encephalopathy and prediction of overt encephalopathy

Background: Subclinical hepatic encephalopathy (SHE) features in 30-84% of patients with cirrhosis of the liver. Its clinical significance with regards to progression to overt encephalopathy has however, not been established. Aims: The present study was conducted (i) to compare the diagnostic usefulness of neuropsychological tests with that of electrophysiological (EP) tests in detection of SHE, and (ii) to examine the natural course of SHE. Methods: Seventy-five-nonencephalopathic cirrhotics (11 females, 64 males; mean (+/- SD) age 43.6 (+/- 11.7) years; mean (+/- SD) education 11(+/- 3) years) were studied using a battery of tests for intelligence and memory, the number connection test (NCT), and EP tests viz. electroencephalogram (EEG) and auditory P300 event related potentials (P3ERP). All the patients were followed up for a period of 6 months to 2 years for development of overt encephalopathy. Results: Thirty-five out of 75(47%) patients were diagnosed to have SHE based on at least one abnormal test result. The P3ERP latencies detected SHE in maximum number of patients (23%) followed by EEG (21%). Nearly 59% of patients with SHE progressed to overt encephalopathy within a mean duration of 4 months. Multivariate analysis showed that prior episode of encephalopathy (RR = 6.3; 95% CI = 2.0-19.7), abnormality on EEG (RR = 7.5; 95% CI = 2.2-25.3), abnormal performance on psychometric battery of tests (RR = 35.2; 95% CI = 4.3-287.3), occurrence of gastrointestinal bleed (RR = 19.3; 95% CI = 4.1-88.9), occurrence of dehydration (RR = 10.7; 95% CI = 2.5-45.4) and infection (RR = 11.4; 95% CI = 2.0-64.4) had significantly higher risk for development of overt encephalopathy. Conclusions: EP methods were more sensitive in detection of SHE. Amongst all the tests used, presence of only an abnormal EEG was significantly associated with development of overt encephalopathy along with the precipitating factors.