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Adult Hypoxic Ischemic Injury

KEY FACTS

TERMINOLOGY

• Hypoxic ischemic injury (HII): Global hypoxic ischemic injury,

global anoxic injury, cerebral hypoperfusion injury

○ Etiologies: Cardiac arrest, cerebrovascular disease,

drowning, asphyxiation

IMAGING

• Injury patterns highly variable depending on brain maturity,

severity, and length of insult

○ Mild to moderate: Watershed zone infarcts

○ Severe: Gray matter structures (basal ganglia, thalami,

cortex, cerebellum, hippocampi)

• MR best to assess overall extent of injury within hours after

HII event

○ DWI: 1st modality to be positive (within hours)

○ DWI: Restriction in deep nuclei ± cortex

○ T2/FLAIR: ↑ signal in cerebellum, basal ganglia, cortex

○ Acute changes not reliably identified with T2

• MRS: More sensitive and indicative of severity of injury in

first 24 hours after HII

○ ↑ lactate, ↑ glutamine-glutamate

TOP DIFFERENTIAL DIAGNOSES

• Ischemic territorial infarction

• Traumatic cerebral edema

• Toxic/metabolic disorder

• Acute hypertensive encephalopathy, posterior reversible

encephalopathy syndrome (PRES)

• Creutzfeldt-Jakob disease

• MELAS

PATHOLOGY

• Common underlying process regardless of cause

○ ↓ cerebral blood flow and ↓ blood oxygenation

○ Switch from oxidative phosphorylation to anaerobic

metabolism

○ Glutamate-related cytotoxic processes

(Left) Axial DTI trace image in

a 21-year-old unresponsive

man shows extensive

hyperintensity related to

cytotoxic edema throughout

the cortex and subcortical WM

ſt as well as the external

capsules ﬇ in this patient

with severe hypoxic ischemic

injury (HII). (Right) Axial T2 MR

in the same patient shows

hyperintensity throughout the

cortex, subcortical WM ſt and

the external capsules ﬇.

Complete effacement of the

sulci is related to gyral

swelling. Involvement of the

visual and sensorimotor cortex

is common in severe HII.

(Left) Axial FLAIR MR shows

symmetric hyperintensity of

the basal ganglia ﬈ and

thalami ſt in this patient

status post cardiac arrest. T2

and FLAIR images typically

become positive in the early

subacute period (> 24 hours to

2 weeks) with increased signal

and swelling of the injured GM

structures. (Right) Axial DTI

trace shows extensive WM

hyperintensity ﬇ related to

cytotoxic edema in this 43-

year-old woman with mild to

moderate HII. DWI signal

abnormalities may

pseudonormalize by the end of

the 1st week.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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