Natural history of minimal hepatic encephalopathy in patients with extrahepatic portal vein obstruction.

OBJECTIVES: Minimal hepatic encephalopathy (MHE) leads to deterioration in patient quality of life and could be a marker for future episodes of clinical hepatic encephalopathy (HE) in liver cirrhosis. Whether MHE predicts HE in extrahepatic portal vein obstruction (EHPVO) is not known. We studied the incidence of overt HE in EHPVO patients with MHE.

METHODS: Consecutive patients (from October 2006 to July 2007) with a diagnosis of EHPVO were followed up at 3-month intervals. MHE was diagnosed by abnormal psychometry (>2 s.d.) and/or P300 auditory event-related potential (P300 ERP) (>2.5 s.d.), and HE was diagnosed as per West-Heaven criteria. Critical flicker frequency (CFF) was also measured at baseline and after 1 year.

RESULTS: Thirty-two EHPVO patients (age, 23.2+/-10.8 years; M/F 22:10) were followed up for 1 year. Of 32 patients, P300 ERP was prolonged in 8 (25%) (371.8+/-13.9 ms), 9 (28%) had abnormal psychometric tests, and CFF was <38 Hz in 8 (25%) patients after a follow-up of 13.5+/-2.4 months. Of 12 patients who had MHE at baseline, 9 (75%) patients continued to have MHE, and in 3 (25%) patients it disappeared. One (5%) of the remaining 20 patients developed MHE during the follow-up. Venous ammonia level was higher in patients with MHE (79.7+/-17.0 micromol/l; range 33-124) compared with patients without MHE (46.6+/-19.8 micromol/l; range 24-78, P<0.001) on follow-up. Similarly, patients who had spontaneous shunts (n=10) had significantly higher venous ammonia levels (82.4+/-20.3 vs. 47.1+/-16.7 micromol/l; P=0.001) than those who had no shunt (n=22). Neither patients who had MHE nor those who did not have MHE at baseline developed HE.

CONCLUSIONS: Seventy-five percent of extrahepatic portal vein obstruction patients with MHE continued to have MHE, and new-onset MHE developed in 5% over 1 year. In this small sample, patients with EHPVO and MHE did not progress to overt encephalopathy within the relatively short time frame studied.