When the preconditions for the clinical determination of brain death cannot be met, what imaging modalities are recommended to determine absence of intracranial blood flow? What findings in each test confirm brain death?
College Answer
Test |
Positive result |
Four vessel angiography |
no blood flow above the carotid siphon in the anterior circulation and no blood flow above the foramen magnum in the posterior circulation |
Radionuclide imaging |
Tc-99m HMPAO scan demonstrating absent intracranial perfusion |
CT angiography |
absent enhancement bilaterally of peripheral intracranial arteries and central veins at 60 seconds. |
Discussion
The answer above borrows heavily from the ANZICS Statement on Death and Organ Donation (I have linked to Version 3.2, from 2013).
In brief, the investigations and expected findings are as follows:
Four-vessel arterial digotal subtraction angiography:
- blood flow should not be demonstrated above the level of the carotid
siphon in the anterior circulation, or above the foramen magnum in the posterior circulation
Tc-99m HMPAO radionuclide (SPECT) scan
- Absent intracranial parenchymal Tc-99m HMPAO uptake
CT angiography
- Absent contrast enhancement, at 60 seconds following bolus injection, bilaterally and of all of the following vessels:
- MCA branches beyond the Sylvian branches
- P2 segment of the PCA
- pericallosal arteries
- internal cerebral veins
- Adequate contrast enhancement of the external carotid artery branches to confirm a technically adequate study.
References
ANZICS Death and Organ Donation Committee, THE ANZICS STATEMENT ON DEATH AND ORGAN DONATION Edition 3.2 2013