Brain Death Definition and Protocols
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So in this section, we're going to
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talk about brain death protocols.
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First of all, I'd like to stress that
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brain death is a clinical definition.
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It's defined by coma, lack of brainstem
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reflexes, and the inability of a
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patient to breathe on their own.
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That is the definition.
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On EEG, typically you'll see no activity.
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On nuclear medicine scans, you'll see the
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absent intracranial uptake throughout the brain.
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It's called the empty light bulb sign.
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On digital subtraction angiography,
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you see no forward flow beyond
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the internal carotid arteries.
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And then we're going to talk
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about CT, CTA, and MRI, MRA.
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So, the arrows in red are things that
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are quite predictive of brain death.
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Again, on CT, CTA, no opacification arteries,
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distal to the internal carotid arteries.
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On MRA, no flow related enhancement
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of the cerebral arteries, distal
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to the internal carotid arteries.
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Loss of the arterial flow
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voids and T2 weighted images.
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and no intracranial perfusion.
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The items in yellow are pretty good
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predictors, more common in patients
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with brain death than with patients
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with edema who don't have brain death.
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And these are low signal or blooming throughout
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all of the arteries and veins is thought to
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be due from increased oxygen extraction and
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from venous stasis and from mass effect.
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that's great enough to
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cause tonsillar herniation.
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The items in white under CTA and green under
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MRI, MRA, are usually seen, but these can
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be partially reversible and cannot really
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differentiate patients in coma who will go on to
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death versus patients who can partially recover.
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So in CT, CTA, it's diffuse cerebral edema
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and loss of gray white differentiation.
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And on MRI, MRA is T2 hyperintensity
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and swelling in the cortex and deep
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brain nuclei greater than white
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matter with restricted diffusion.
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Same is true of brainstem hemorrhage
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and hyperintensity in the brainstem.
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It may predict a worse prognosis, but it's
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not specifically predictive of brain death.
Pamela W Schaefer, MD, FACR
Professor of Radiology, Vice Chair of Education
Massachusetts General Hospital
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