Demonstration of arrested intracerebral blood flow is the ultimate evidence of brain death. Computerized radionuclide cerebral flow study was done on 18 patients diagnosed clinically as brain dead. Correlation was made with clinical neurophysiological and EEG findings. The criteria for diagnosis of arrested intracerebral perfusion using radionuclide flow study were: non-visualization of blood flow activity in the intracranial arteries during the arterial phase, diffused cerebral activity during the capillary phase and non-filling of venous sinuses during the venous phase; visualization of typical 'hot nasal' activity; the time activity curve over the cerebral hemispheres lacks a bolus effect and instead shows a delayed gradual rise of activity. These features are pathognomonic of brain tamponade.
Arrested intracranial circulation was seen in 16 patients (ten had electrocerebral silence; one had extremely abnormal EEG with small voltage activity and five had no EEG done). In the remaining two patients, some cerebral blood flow was demonstrated (one had no definite cerebral activity and the other had diffused EEG activity).
Radionuclide cerebral flow study is a very sensitive, accurate, safe, simple, rapid and non-invasive modality in confirming brain death and is especially useful in patients on "brain-protection" regime, in hypothermia or in certain metabolic states where diagnosis based on clinical and EEG criteria is difficult. EEG need not be a required procedure once brain death is established by the demonstration of arrested intracranial circulation.