Plasma gamma aminobutyric acid concentrations provide evidence of different mechanisms in the pathogenesis of hepatic encephalopathy in acute and chronic liver disease.

Plasma gamma aminobutyric acid (GABA) concentrations were measured using a radioreceptor assay in 24 patients with acute liver disease with and without clinical encephalopathy; 15 patients with chronic liver disease with and without clinical encephalopathy, and 16 control subjects with no evidence of liver disease or hepatic dysfunction. Plasma GABA concentrations were significantly elevated in the patients with acute liver disease and clinical encephalopathy as compared with the controls. There was a positive relationship between the clinical grade of encephalopathy, the changes in the EEG and the plasma GABA concentrations. Plasma GABA concentrations in patients with chronic liver disease did not relate to the clinical grade of encephalopathy or the changes in the EEG. It is concluded that elevated plasma GABA concentrations are in keeping with the pathogenesis of encephalopathy in acute liver disease, but not in chronic liver disease.