Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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August 27, 2015
Brain Death
- Background:
- Brain death is the complete and irreversible loss of brain function, including involuntary activity.
- Its is a medicolegal term very important in the setting of living donor organ donation.
- Clinical Features:
- Usually determined by clinical neurological examination (loss of brain stem reflexes). However, for ICU patients, clinical evaluation may be difficult due to use of CNS depressants.
- In these difficult cases, EEG and demonstration of absent cerebral blood flow are used as ancillary methods for confirmation of brain death.
- Key Diagnostic Features:
- Absence of blood flow in the supraclinoid ICA with maintained flow in the ECA demonstrated by cerebral angiography, CTA, or cerebral scintigraphy is a very specific indicator of brain death.
- MRI /MRA is not yet accepted as an ancillary test for establishing brain death. However, recent studies have shown that tonsillar herniation, loss of T2 flow void in intracranial vessels, and nonvisualisation of IC vessels in TOF MRA may be useful indicators of brain death.
- DWI may show diffuse reduction of ADC values throughout the brain parenchyma. However, the ADC reduction depends on the time of insult and may show pseudonormalization phenomenon, making them less reliable.
- CT perfusion may show matched decrease in CBV and CBF in the brainstem or the entire brain parenchyma. The role of perfusion studies in confirmation of brain death is under evaluation.
- DDx: Bilateral ICA occlusion
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