[Validity of the electroencephalogram and evoked potentials in the diagnosis of brain death]

Alterations of electroencephalogramm and evoked potentials in brain dead patients are known. We are going to discuss the value of the various parameters as well as their comparison with the clinical symptoms. Newer guidelines recommend the brain-stem acoustic evoked responses, too. So we analysed those comatose patients requiring for artificial respiration in whom brain stem acoustic responses could not be evoked. We found 21 patients out of 103 unselected consecutive patients with primary cerebral disease. All patients with isoelectric EEG were brain dead. Absence of acoustic response was not sure combined with clinical symptoms of brain death. Earlier SSEP components were frequent, deformed flash evoked potentials were found in all brain dead patients. In all brain dead patients there was an absence of early acoustic evoked responses and an isoelectric electroencephalogramm. The longer the symptoms of brain death lasted, the more complete the disappearance of evoked potentials was. The investigations demonstrate the value of clinical examination and electroencephalogramm in the diagnosis of brain death, but also point to the value of evoked potentials as additional parameter, esp. in order to get informations of the pathophysiological mechanisms leading to death.