Fat Emboli Cerebral Infarction

KEY FACTS

TERMINOLOGY

• Acute stroke related to fat emboli

IMAGING

• Acute ischemia with appropriate clinical history

○ Long bone or pelvic fractures, cardiac surgery, joint

replacement surgery

• Often mimics thromboembolic stroke

• Commonly affects both gray and white matter

○ May affect deep and periventricular white matter

○ May affect deep gray nuclei

• May involve typical vascular territory

• May mimic "watershed" infarct

• NECT: Typically negative acutely

○ Hypodense MCA sign related to fat within MCA

• T2WI: Multiple small, scattered hyperintense foci

• DWI: Acute diffusion restriction

TOP DIFFERENTIAL DIAGNOSES

• Acute cerebral ischemia-infarction

• Acute hypertensive encephalopathy, PRES

• Vasculitis

PATHOLOGY

• Fat emboli can pass through pulmonary capillaries without

shunting lesions and result in systemic embolization (brain,

kidneys most commonly)

CLINICAL ISSUES

• Fat embolism syndrome: Pulmonary, CNS, and cutaneous

manifestations

○ Hypoxia, deteriorating mental status, petechiae

• Neurological dysfunction varies from confusion to

encephalopathy with coma and seizures

• Uncommon but potentially life threatening

• Fat embolism syndrome after fractures: Up to 2.2%

(Left) Axial DWI MR shows

innumerable punctate foci of

restriction ﬇ throughout the

white matter and gray matter

of this 68-year-old patient

with mental status changes

post hip surgery. Note the

extensive involvement of the

basal ganglia and thalami.

(Right) Axial DWI in the same

patient shows the extensive

foci of restriction ﬇ related

to acute ischemia from the

patient's fat emboli. Note the

more focal involvement of the

left middle carotid artery

territory with frontal and

temporal lobe involvement.

(Left) Axial FLAIR MR in the

same patient shows minimal

abnormal hyperintensities in

the deep gray nuclei and

periventricular white matter.

Diffusion imaging is the most

sensitive sequence for acute

stroke imaging. (Right) Axial

DTI trace shows 2 punctate

foci of restriction related to

fat emboli in this 39-year-old

trauma patient with bilateral

acetabular fractures. DTI may

be more sensitive than DWI in

acute ischemia. Imaging of fat

emboli often mimics a typical

thromboembolic stroke.

Trauma, and Stroke

Brain: Pathology-Based Diagnoses: Malformations,

101