The brain-stem and 40 Hz middle latency auditory evoked potentials in brain death

Bilateral recordings of brain stem auditory evoked responses were compared with the 40 Hz middle latency auditory evoked responses in 38 patients either brain dead or in coma grade IV. In 4 cases the 40 Hz auditory evoked potential was partly preserved, while the brain stem auditory evoked potential was not reproducible beyond wave II. Recording of the 40 Hz auditory evoked potential is found to be more sensitive in some rare instances.