Brain Death

KEY FACTS

TERMINOLOGY

• Brain death (BD); death by neurological criteria (DNC)

• Complete, irreversible cessation of brain function

IMAGING

• No flow in intracranial arteries or venous sinuses

○ No intravascular enhancement on CT or MR

○ Light-bulb sign on radionuclide study

• Diffuse cerebral edema

○ Gyri swollen, ventricles/cisterns compressed

○ Gray-white matter borders effaced

TOP DIFFERENTIAL DIAGNOSES

• Reversible diffuse cerebral edema

○ Drug overdose

○ Status epilepticus (clinically can mimic BD)

○ Acute metabolic dysfunction (e.g., fulminant hepatic

failure)

• Technical difficulty

○ Missed bolus (nuclear study, CTA)

○ Dissection (catheter angiography)

○ Vasospasm (catheter angiography)

• Massive cerebral infarction/edema

PATHOLOGY

• Severe cell swelling, ↑ intracranial pressure

CLINICAL ISSUES

• Complex assessment, often misunderstood by

nonspecialists and families

○ DNC highly reliable with

– Experienced examiners

– Using established criteria

• Imaging may confirm but does not substitute for clinical

criteria

• Reversible causes of coma must be excluded

• Remember: BD is primarily clinical diagnosis, legal criteria

vary

(Left) Axial NECT shows

complete loss of gray-white

matter differentiation and

diffuse sulcal and gyral

effacement in this patient

with diffuse cerebral edema

and clinical brain death. The

lateral ventricles are also

effaced posteriorly ſt. (Right)

Anteroposterior Tc-99m

HMPAO scan shows the classic

light-bulb ﬉ and hot-nose

signs ſt related to lack of

intracerebral blood flow in

brain death. No radionuclide is

seen in the intracranial

arteries or veins. (Courtesy B.

Vomocil, MD.)

(Left) Antemortem axial T2WI

in a 50-year-old woman with

clinical brain death obtained

just before death shows small

ventricles and swollen gyri

with near-complete

obliteration of the surface

sulci. (Right) Submentovertex

maximum intensity projection

(MIP) view of MRA in the same

patient shows flow only in

extracranial branches of the

external carotid arteries ſt.

No flow is present in the

intracranial vasculature.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

50