BACKGROUND AND AIMS:Minimal hepatic encephalopathy (MHE) is associated with poor quality of life and increased work disability in cirrhotic patients. Its prevalence in extrahepatic portal vein obstruction (EHPVO) is not known. We studied the prevalence of MHE in EHPVO patients and utility of critical flicker frequency (CFF) for diagnosing MHE.PATIENTS AND METHODS: Thirty-four EHPVO patients with a history of variceal bleed (age 23.2 ± 11.2 yr, M:F 22:12) diagnosed by either Doppler US or MR angiography, which demonstrated portal vein obstruction and/or portal vein cavernoma, were evaluated by psychometry (number connection tests A, B or figure connection tests A, B) and P300 auditory event-related potential (P300ERP). CFF was also evaluated. MHE was diagnosed by abnormal psychometry (>2 standard deviation [SD]) and/or P300ERP (>2.5 SD).RESULTS:Prevalence of MHE (N = 12) was 35.3%. Of 34 patients, P300ERP was abnormal (380.0 ± 28.9 msec) in 11 (32%), psychometry in 9 (26.4%), both P300ERP and psychometry in 8 (23.5%), and CFF <38 Hz in 7 (21%) patients. Six (67%) patients with abnormal psychometry and 7 (64%) with abnormal P300ERP had CFF below 38 Hz. CFF had sensitivity (75%), specificity (96%), positive predictive value (86%), negative predictive value (93%), and diagnosis accuracy of 91% when compared to patients with both abnormal psychometry and P300ERP. The venous ammonia level was higher in patients with MHE (83.1 ± 29.7 vs 44.7 ± 16.1 μmol/L, P < 0.001) compared to patients without MHE. Spontaneous shunts were present in 67% of patients with MHE compared to 14% of non-MHE patients. MHE was more common in patients with spontaneous shunts (72.7% vs 17.4%, P= 0.001) than without spontaneous shunts.CONCLUSIONS:Prevalence of MHE in EHPVO patients is 35.3%, and CFF alone can reliably diagnose 88% of MHE patients with both abnormal psychometry and P300ERP. However, in view of the relatively low number of patients with MHE, the usefulness of CFF in this setting awaits confirmatory studies.