Brain death: use of dynamic CT and intravenous digital subtraction angiography.

Brain death results when irreversible intracranial circulatory arrest, involving both the internal carotid and intracranial vertebral basilar systems, occurs despite preservation of ex­ tracranial circulation . To document the absence of intracranial blood flow and establish the irreversibility of the condition, intraarterial cerebral angiography and radionuclide cerebral angiography have become the accepted imaging means of confirming a clinical diagnosis of brain death. After encoun­ tering cases in which the radionuclide angiogram was equiv­ ocal and cerebral arteriography was therefore required for confirmation, we undertook to study the ability of intravenous digital subtraction angiography (DSA) and dynamic CT to diagnose brain death. Five patients for whom it was necessary to confirm a clinical diagnosis of brain death had radionuclide cerebral angiography, intra­ venous cerebral DSA, and dynamic cerebral CT. Final diagnoses in the five patients, re spectively, were intracranial hemorrhage due to coarctation of the aorta (age of patient, 22 years), hypertensi ve intracranial hemorrhage (t wo pati ents, ages 62 and 35 years), trau­ matic intracranial hemorrhage (age of patient, 4 years), and ruptured posterior communicating artery aneurysm (age of patient, 63 years) . Each patient's clinical diagnosis of brain death was based on cerebral unresponsivity, absent brainstem (cephalic) reflexes, and electroen­ cephalographic cerebral silence (four patients) and/or posi tive apnea test (four patients). Intravenous cerebral DSA was performed with a 6.3 F catheter positioned in the right atrium via the femoral vein. Contrast material (meglumine diatrizoate 60%) was inj ected at 30 ml/sec for 1 sec and anteroposterior images of the head were obtained at one frame/sec for 30 sec. Rapid sequence (d ynamic) CT studies were performed with a GE 8800 CT/T scanner, using a scan time of 4. 8 sec and an interscan delay of 1.2 sec. Inj ection of meglumine diatri zoate 60% contrast material at a rate of 8 ml/sec for 4 sec was made through the indwelling right atrial catheter. Scanning began simultaneously with contrast injection so that an initial baseline image would be acquired before arrival of the contrast bolu s. Six sequential im ages were made over 36 sec at a single level of the brain selected to include the frontal , parietal, and occipital lobes at the level of the lateral ventricles. A second dynamic sequence was then made at the level of the fourth ventricle , to include the posteri or fossa. Time­ density graphs plotting the change in CT numbers in specifi ed reg ions of intere st (ROI) in the cerebral and cerebellar hemi spheres were then made using scanner computer software. Large areas of interest including most of each cerebral or cerebell ar hemisphere were used (Fig s. 1 and 2A). Absence of any intracranial bolu s effect was then confirmed by multiple smaller ROI coverin g all included porti ons of the brain . Confirmation of technically adequate bolu s with preserved external carotid flow was done with small ROI in the scalp and/or neck ti ssues (Fi g. 2B). Results In all five cases, both IVDSA and dynamic CT demonstrated an absence of intracranial blood flow. Radionuclide cerebral angiography also indicated absent intracranial circulation in all patients. These findings , added to the clinical test findings of electroencephalographic cerebral silence and/or positive apnea test, resulted in a final diagnosis of brain death in all patients.