Evaluation of Critical Flicker Frequency in Detecting and Monitoring Minimal Hepatic Encephalopathy

BACKGROUND: Minimal hepatic encephalopathy (MHE) is defined as presence of abnormal neuropsychological and/or neurophysiological tests in cirrhotic patients without clinical signs of overt HE. Detecting MHE with available tests is time consuming, semi-objective, dependent on psychomotor skills of the patient and requires qualified personnel for administering test. Of late Critical Flicker Frequency (CFF) has emerged as a new diagnostic test for detecting MHE which obviates the above problem. AIM: To find out the prevalence of MHE in a group of adult cirrhotic patients with no overt HE, at a tertiary health care center using CFF analysis and assess changes in the same after four weeks of oral L-ornithine L-aspartate (LOLA) administration in subset with abnormal CFF. METHODS: 25 adult patients with cirrhosis, diagnosed on basis of clinical parameters & lab investigations, were invited to participate in the study. In patients without signs of overt encephalopathy (N=20) CFF analysis was done by HEPAtonorm analyzer. Cut off of 39 Hz was used, below which result was taken as abnormal and diagnostic of MHE. Patients with abnormal result (n=10) were given oral LOLA 30gm/day for 4 weeks. Repeat CFF analysis was done after 4 weeks in 13 patients, comprising 10 patients with abnormal and 3 patients with normal result in first study. Results were analyzed using non-parametric statistical tests. RESULTS: Of 20 patients without overt HE (M: F-12: 8) (Median age 43 years [25-73yrs]) etiology was alcohol/cryptogenic/viral (B/C) in 4/7/9 (3/6), Child's status A/B/C in 5/7/8 respectively. The prevalence of MHE in cirrhotic patients was found to be 50% (10/20) and all of them had advanced cirrhosis (Child B/C). Subgroup of patients with MHE treated with LOLA for 4 weeks showed improvement in CFF test results repeated after 4 weeks (p=0.008) while those with no MHE showed insignificant change in their CFF after 4 weeks (p=0.85), signifying reproducibility & lack of learning effect. CONCLUSIONS: CFF measurement is a simple and reliable tool for detection of MHE. It also has high degree of reproducibility & lack of learning effect on repeated testing in the same patient. It provides an objective parameter for assessment of improvement in MHE by pharmacological intervention. CFF should be used more often to diagnose and monitor MHE in patients with advance cirrhosis.