Multimodality evoked potentials and electroretinography in a test battery for an early diagnosis of brain death

A test battery conformed by multimodality evoked potentials (MEP) and electroretinography (ERG) was applied to 30 brain-dead patients. Three patterns of brainstem auditory evoked potentials (BAEPs) were observed: (1) No identifiable waves (73.34%); (2) an isolated bilateral wave I (16.66%) and (3) an isolated unilateral wave I (10%) (Fig. 1,2,3). Waves II, III, IV, and V were not observed in any of the cases. Whenever wave I was recorded, it was always significantly delayed. For short latency evoked potentials (SSEPs) a characteristic pattern was found: absence of cortical N20 and later responses in scalp-cephalic records and preservation of the so-called subcortical components in the rest of the derivations. For visual evoked potentials (VEPs) and electroretinography (ERG) the same pattern was found in all cases: when a cephalic reference was used for both, VEPs and the ERG, waves a and b of the ERG were recognized in all cases. The visual evoked responses consisted of waves with less amplitude but very similar in latency and morphology to the ERG. When a non-cephalic channel was chosen for the ERG and VEPs, the ERG waves showed no changes either in morphology or in latency, while the VEP lead showed no response. It is discussed that the consideration of MEP and ERG in a battery test to evaluate brain-dead patients increase diagnostic reliability, which is fundamental for an early diagnosis of brain death.