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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.

Report

Faculty

Pamela W Schaefer, MD, FACR

Professor of Radiology, Vice Chair of Education

Massachusetts General Hospital

Tags

Vascular Imaging

Neuroradiology

Neuro

MRI

Head and Neck

CT

Brain

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