Visual evoked potential recordings in hepatic encephalopathy and their variations during branched chain amino-acid treatment.

In fourteen subjects with various stages of hepatic encephalopathy (HE), Visual Evoked Potential (VEP) recording and blood ammonia (NH3), octopamine (OCT) and phenylethanolamine (PEA) determinations were performed before and during a four-day treatment with branched chain amino acid (BCAA) i.v. infusion. All the subjects with HE showed significant basal VEP alterations, namely an increased latency and a lowered amplitude of the P100 wave, in comparison with a control group of 26 normal subjects. A significant improvement in P100 wave amplitude occurred just about 60' after the beginning of BCAA infusion, while P100 latency was still unaffected, as were OCT, PEA and NH3 levels. After the fourth day of BCAA treatment, both P100 wave amplitudes and latencies were strongly improved, together with OCT, PEA and NH3 levels. VEP improvements seemed to be well correlated with HE clinical evolution, and were able to detect modifications of central nervous system reactivity earlier than serum parameters.