Cerebral Emboli: Financial Disclosure What you need to know! Emboli - Torres... · Cerebral Emboli: What you need to know! Carlos Torres, MD, FRCPC. Associate Professor of Radiology

Cerebral Emboli: What you need to know!

Carlos Torres, MD, FRCPC.

Associate Professor of RadiologyDepartment of Radiology, University of OttawaOttawa, ON, [email protected]

Financial Disclosure

None

• Review multiple uncommon sources of cerebral embolism and describe their key imaging features on CT and MRI.

Learning Objective

• The heart and the carotid arteries are the most common sites of origin of embolic disease to the brain

• Emboli consist mainly of red blood cells, platelets and fibrin.

• Emboli with different composition: air, fat, calcium and tumor cells.

• Some could have a different site of origin: venous system.

• Infarcts: end result of any type of embolism

Introduction

Carotid atherosclerotic disease

CTA

Common sources of cerebral embolism Free floating thrombus - FFT

Menon B, et al. Neuroradiology. 2010 Nov;52(11):1055-6.

The “donut sign” on CTA

Jaberi A, Lum C, Torres C et al Neuroradiology. 2014 Jan;56(1):15-23.

The “finger sign” on CTA

• Emboli lodge in proximal intracranial arteries: territorial infarcts

• Smaller emboli lodging distally in terminal cortical branches: small wedge-shaped peripheral infarcts

• Multiple acute small infarcts in different vascular territories suggests embolic origin

• DDX: Vasculitis and anatomical variants connecting the ant and post circulations (e.g.: fetal PCA and PTA)

General Features of Cerebral Emboli Typical pattern of embolic infarcts

DWI

Clinical scenarios …

C/o Mauricio Castillo, UNC Chapel Hill

Case 130 y/o pt involved in MVA…fx of the femur.


… coma 2 days after fixation

Case 1

DWI

30 y/o pt involved in MVA…fx of the femur.


… coma 2 days after fixation Case 1 30 y/o pt involved in MVA…fx of the femur.

SWIDWI

Initial CT –Tx work up

Follow up CT: Crazy paving

Petechiae

Fat embolism syndrome

Petechiae

Fat embolism syndrome

Crazy paving

Triad: - Pulmonary (hypoxia 95%)- CNS (confusion 60%)- Skin (petechial rash)

Star field appearance

• CFE is a consequence of fractures: long bones and pelvis

• Orthopedic procedures, bone infarcts in sickle cell disease and acute hemorrhagic pancreatitis

• Triad of pulmonary and neurological dysfunction and petechial rash.

Cerebral Fat Embolism

• Theory: exposure of medullary fat to damaged blood vessels with fat mechanically forced into the venous system

• Fat emboli cross the pulmonary circulation and reach the intracranial circulation even without an intracardiac shunt being present

• Fat emboli occlude capillaries: ischemia and cytotoxic edema

• The fat globules are deformable and tend to breakup into smaller ones which recycle through the pulmonary circulation

• Occlusions tend to be temporary and changes may be reversible

Cerebral Fat Embolism Imaging Findings

• DWI: multiple foci of high signal scattered throughout the brain

• The “star field” appearance is the most common imaging pattern yet it remains nonspecific

• These foci are thought to represent cytotoxic edema in acute infarct

• As the occlusions are temporary, the findings can be reversible

Imaging Findings

• DWI: multiple foci of high signal scattered throughout the brain

• The “star field” appearance is the most common imaging pattern yet it remains nonspecific

• SWI shows innumerable foci of blooming c/w microhemorrhage

Case 256 y/o pt, stroke code, right sided weakness…

Calcified embolus from calcified carotid plaque

Zakhari N, Castillo M, Torres C. Neuroimag Clin N Am. Feb 2016. Vol. 26 (1): 147-163.

Case 256 y/o pt, stroke code, right sided weakness…

Follow up study 24h later

Companion case:68 y/o pt, stroke code, left sided weakness…

Infarcts secondary to calcific emboli


• Calcified cerebral embolism is an uncommon cause of stroke (3%)

• Can occur spontaneously or secondary to surgery and catheterization

• Sources of emboli: heart, aortic arch and neck arteries

• Most common sources: calcified aortic valve and carotid atherosclerosis

Calcified cerebral emboli

•On CT, calcified emboli are small (2–3 mm) round or ovoid hyperdensities (162 HU)

•The “salted pretzel” sign is near pathognomonic on CT

• Multiple calcified peripheral emboli in arteries along the pial surfaceof the brain like salt on a pretzel

•Differential Dx :

- arterial wall calcification which appears more linear - congenital infections, tuberous sclerosis - remote intrathecal administration of Pantopaque contrast media

Calcified cerebral emboli

Case 350 y/o pt, biopsy for tiny nodule

Case 3confusion and left sided weakness after lung biopsy

Air embolism post lung biopsyZakhari N, Castillo M, Torres C. Neuroimag Clin N Am. Feb 2016. Vol. 26 (1): 147-163.

Air in ascending aorta Air in the left ventricular apex


Another case …

• Introduction of air into arterial or venous circulations is mostly iatrogenic

• Can occur in a variety of procedures including:- percutaneous lung biopsy- cardiac surgery with cardiopulmonary bypass- angiography and intravascular catheters

• Non-iatrogenic causes of air embolism: - penetrating thoracic and cranial Tx and decompression sickness

• Accidental ingestion of hydrogen peroxide –an industrial bleaching agent– has also been reported to cause arterial or venous gas embolism as it decomposes into oxygen and water after absorption.

Cerebral air embolism

• Venous air may reach the arterial circulation through an intracardiacshunt or by overwhelming the pulmonary filtering mechanism.

• Cerebral arterial air emboli block small arteries leading to infarct

• The only effective treatment is hyperbaric oxygen treatment

• Improves oxygenation of ischemic tissues and resolves the mechanical vascular occlusion

Cerebral air embolism

Infectious aneurysm, endocarditis

Case 442 y/o pt, severe headache and right sided weakness … endocarditis

• Septic emboli are the presenting symptom of IE in up to 47% of patients

• The risk of embolic events increases with:

- Staphylococcus aureus as the causative organism- Mitral valve involvement - Vegetations > 3cm in size

Septic emboli

• Septic emboli may produce:

- embolic infarcts- cerebral hemorrhage- less likely mycotic /infective aneurysms and cerebral abscesses

Septic emboli

• Cerebral hemorrhage

• Microbleeds: most common abnormality in asymptomatic patients

• Microhemorrhages seen on GRE in IE tend to be cortical in location

Septic emboli

• Develop due to infection and destruction of the vessel wall from the lumen or due to embolization of the vasa vasorum

• Infectious aneurysms tend to be:

- multiple (up to 28%)- fusiform - located in peripheral branches, most commonly MCA (55%)

Septic emboli

Infectious aneurysms:

Infectious left MCA aneurysm, Staph aureus mitral valve IE


Pt with known endocarditis and previous infarcts, on antibiotics

Companion case:



… deterioration of the patient’s clinical condition

… deterioration of the patient’s clinical condition

Rapidly developing infectious basilar tip aneurysm


• Proximal infectious aneurysms occur in approximately 1/3 of cases

• Multiplicity and rapid morphologic changes favor infectious aneurysms over other types

• Treatment: antibiotics as well as endovascular therapy or surgery.

• Response to antibiotics is highly variable with possible regression and resolution, rupture or even de novo aneurysm formation

Infectious aneurysms Case 546 y/o pt, slurred speech…stroke code Hx of cardiac myxoma

Myxomatous left MCA aneurysm


Embolism from cardiac myxoma

• Cardiac myxoma: most common primary cardiac tumor in adults (83%)

• Most common location: left atrium (83%-88%)

• 3rd – 6th decades of life with a 2:1 female predominance

• Systemic embolization is a known complication of this tumor (50% pts)

• Embolization occurs due to:

- surface thrombi - erosion and fragmentation of the tumor itself (tumor particles)

Embolism from cardiac myxoma

• Myxomatous tumor emboli may result in cerebral aneurysm formation

• Theory for aneurysm formation:

Transendothelial invasion of the arterial wall by tumor cells with subintimal growth and disruption of the wall architecture leading toweakening and subsequent aneurysm formation

• Myxomatous aneurysms tend to be fusiform in shape, peripheral in location and may be multiple and similar to infectious aneurysms

• 74% myxomatous aneurysms involve the middle cerebral arteries

Case 6 58 y/o pt with headache and visual disturbance


Case 6 …images from same CTA

Emboli in the pulmonary arteries and their branches

Paradoxical embolism


Paradoxical embolism (PDE)

• Suspected in patients with embolic stroke in absence of cardiac or proximal arterial sources

• Requires: - venous thrombosis - systemic embolization- abnormal communication between arterial and venous circulations- a pressure gradient favoring a right to left shunt.

• The abnormal communication can be intra-or extra-cardiac (pulmonary arterio-venous malformation)

• The defect is most commonly a patent foramen ovale

• Most common source of PDE is venous thrombosis in the legs

Paradoxical embolism (PDE)

• PDE is one of the mechanisms of cryptogenic stroke:

- increased prevalence of pelvic DVT - high incidence of lower limb DVT and PFO

• Attention to ancillary findings on CTA (e.g. pulmonary embolism) may provide clue to the Dx

Case 7 49 y/o pt with decreased LOC

Multiple embolic infarcts and suspected meningitis

… and fever

Case 7

Left atrial ablation 5 weeks before

Atrio-esophageal fistula

Embolization secondary to atrio-esophageal fistula (AEF)

• AEF is a rare (0.04%) and devastating complication of left atrial ablation for treatment of atrial fibrillation

• The presentation is usually delayed, 1–6 weeks after the procedure

• Postprandial transient ischemic attack associated with fever has been described as one of the leading clinical manifestations

• AEF may give rise to variable types of emboli including:

- food particles and air extending into the left atrium from the esophagus - thrombus formation within the left atrium

• These emboli may manifest as embolic infarcts, air embolism, meningitis

Embolization secondary to atrio-esophageal fistula (AEF)

Conclusion

• Aware of unusual sources of cerebral emboli

• Clinical history is key!

• Specific imaging patterns:

- diffuse white matter microhemorrhage in fat embolism - salted pretzel sign in calcified emboli- ancillary findings on CTA of the head and neck


Carlos Torres, MD, FRCPC.

Associate Professor of RadiologyDirector Neuroradiology Fellowship Program Department of Radiology, University of OttawaOttawa, ON, [email protected]

Thank you!

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Cerebral Emboli: Financial Disclosure What you need to know! Emboli - Torres... · Cerebral Emboli: What you need to know! Carlos Torres, MD, FRCPC. Associate Professor of Radiology