Minimal hepatic encephalopathy detection by neuropsychological and neurophysiological methods and the role of ammonia for its diagnosis

Minimal hepatic encephalopathy has been systematically investigated in cirrhotic patients. Although, there are controversies regarding the best methods as well as the role of ammonia for its diagnosis. To evaluate the frequency of minimal hepatic encephalopathy diagnosed by neuropsychological and neurophysiological methods in cirrhotic patients, as well as possible associated risk factors for this condition, including the role of arterial ammonia concentrations for its diagnosis. Cirrhotic patients were evaluated by the number connection test parts A and B (NCT-A and NCT-B), and auditory evoked-related potentials (P300). Minimal hepatic encephalopathy was diagnosed by the presence of abnormal P300 and in unless one of the performed neuropsychologic tests. Arterial ammonia concentration, scholarity and cirrhosis severity accessed by Child-Pugh classification were evaluated in all. Forty-eight cirrhotic patients were evaluated, with median age 50 +/- 8 years old, 79% male. The main etiologies were alcoholic and viral. The P300 was abnormal in 75% of cases, while NCT-A and NCT-B were abnormal in 58% and 65%, respectively. The NCT-B results were influenced by scholarity. The minimal hepatic encephalopathy frequency was 50%. Arterial ammonia concentration was not significantly increased in minimal hepatic encephalopathy diagnosed patients (195 +/- 152 mmol/L versus 148 +/- 146 mmol/L; P>0,05). There was no difference between groups with or without minimal hepatic encephalopathy in the other studied variables. Minimal hepatic encephalopathy is a frequent condition in cirrhotic patients. The arterial ammonia concentration does not play a major role in its diagnosis.