Neuroimaging of Stroke Neuroimaging of Stroke

Andrew Perron, MDAndrew Perron, MD

AAssistant Professorssistant ProfessorDepartment of Emergency MedicineDepartment of Emergency Medicine

University of VirginiaUniversity of VirginiaCharlottesville, VACharlottesville, VA

Andrew Perron, MD

Case PresentationCase Presentation

• Community ED

• No Neurologist

• Radiologist…65 minutes away

• No teleradiology

• CT scanner

Andrew Perron, MD

Case PresentationCase Presentation

• 58 year old female

• 2 hours 15 minutes of dysarthria, right sided weakness

• “Mildly obtunded” per EMS

• Code Stroke called (gets you and CT scan tech ready)

Andrew Perron, MD

Case PresentationCase Presentation

• Dysarthric, weak RUE/RLE, NIHSS = 18• Toes up-going bilaterally• Family relates a few weeks of left arm tingling and

clumsiness• Off to CT…returns with the films on the bed• Nurse asks if you are going to read the CT, since

only 15 minutes left before the 3 hour mark (Radiologist still 45 minutes away)

Andrew Perron, MD

Head CTHead CT

Andrew Perron, MD

Andrew Perron, MD

Cranial CT ScanningCranial CT Scanning

• First line imaging study in suspected stroke patients– Exquisite sensitivity for the detection of

blood– Ubiquitous in hospitals

• Fundamental branch point in the work up of a suspected stroke patient

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3 Possible CT Findings3 Possible CT Findings

• Stroke Mimic– Non-stroke mass lesion (Abscess, Tumor)– Intracerebral Hemorrhage– Subarachnoid Hemorrhage

• Normal CT

• Cerebral Infarction

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Stroke MimicsStroke Mimics

• Tumor• Blood clot–EDH–SDH

• SAH• IPH• Abscess

Andrew Perron, MD

Stroke MimicsStroke Mimics• Blood clot

EDH SDH

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Stroke MimicsStroke Mimics• Subarachnoid Hemorrhage

Andrew Perron, MD

Stroke MimicsStroke Mimics• Subarachnoid Hemorrhage

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Stroke MimicsStroke Mimics

• Intraparenchymal Hemorrhage/IVH

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CT scan fundamentalsCT scan fundamentals

• Even 3rd and 4th generation scanners will not demonstrate acute ischemic stroke in the first few hours–“Normal CT Scan” is the most

common CT finding in the patient with acute stroke

Andrew Perron, MD

CT scan fundamentalsCT scan fundamentals

• Gray matter is more susceptible to ischemia than white matter–More metabolically active

• Loss of gray-white differentiation is the earliest CT change–Due to edema in the gray matter

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Grey-White DifferentiationGrey-White Differentiation

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CT scan fundamentalsCT scan fundamentals

• Subtle edema can be seen in < 1 hour• By 6 hours, 3/4 of patients with MCA

strokes will show edema in the insular cortex– “Insular Ribbon Sign”

• After12-24 hours, additional edema is recruited into the area– Lesion will become conspicuous on CT

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Cerebral InfarctionCerebral Infarction

• Hyperdense Artery Sign

• Insular Ribbon Sign

• Loss of Cortical Gray-White Differentiation

• Mass Effect

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Hyperdense Artery SignHyperdense Artery Sign

• Typically MCA, PCA, or ACA

• Indicates a major vessel occlusion with thrombus formation

• False positives can occur– Unilateral calcification

• ICA or MCA proximal trunk occlusions more serious than occlusions of MCA branches, PCA, or ACA

Andrew Perron, MD

Hyperdense Artery SignHyperdense Artery Sign

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Hyperdense Artery SignHyperdense Artery Sign

• Whether the at risk territory will undergo ischemic necrosis is a matter of collateral blood supply

• Therefore, this is NOT an infarct sign– Indicates the volume of at risk tissue• If collateral supply fails• Recanalization not achieved

Andrew Perron, MD

Insular Ribbon SignInsular Ribbon Sign

• Area of extreme gray-white differentiation in the MCA artery territory

• Located between the sylvian fissure and the basal ganglia

• Supplied by perforators off of the MCA

Andrew Perron, MD

Insular Ribbon SignInsular Ribbon Sign• Loss of the insular stripe is one of the

earliest indications of MCA stroke

• Normal stripe = Thin white line (gray matter) adjacent to darker gray line (subcortical white matter)

• Ischemia effects metabolically active gray-matter– Causes intracellular edema

Andrew Perron, MD

Insular Ribbon SignInsular Ribbon Sign

Andrew Perron, MD

Insular Ribbon SignInsular Ribbon Sign

• With ischemia– Insular stripe is lost– Homogeneous appearance is noted

• NOT an exclusion criterion for thrombolytic therapy

• Should prompt re-confirmation of stroke ictus reported by patient/family

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Loss of Cortical Loss of Cortical Gray-White DifferentiationGray-White Differentiation

• Similar process as loss of insular stripe

• Loss of cortical gray-white indicates edema in metabolically active gray-matter

• ECASS studies have suggested withholding t-PA from patients with > 1/3 of the MCA territory effected by de-differentiation– Increased risk for hemorrhagic conversion

Andrew Perron, MD

Loss of Cortical Loss of Cortical Gray-White DifferentiationGray-White Differentiation

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Loss of Cortical Loss of Cortical Gray-White DifferentiationGray-White Differentiation

• No similar rules for anterior/posterior circulation

• Interobserver consistency for defining 1/3 of MCA territory de-differentiation is low

• Use as an exclusion criterion is controversial

Andrew Perron, MD

Mass EffectMass Effect

• Brain swelling is extremely subtle in the first hours after arterial occlusion– Sulcal effacement– CSF space compression– Ventricular shift

• Swelling often not visible for the first 6 hours

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Mass EffectMass Effect

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Mass EffectMass Effect

• In ECASS, 21% of initial CT scans demonstrated focal brain swelling–Associated with a poorer outcome

• Use as an Exclusion Criterion is controversial

Andrew Perron, MD

Summary for t-PA: Summary for t-PA: InclusionInclusion

• No evidence of :– Hemorrhage• EDH/SDH• IPH• SAH

– Non-stroke etiology• Tumor• Abscess• Trauma

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Summary for t-PA: Summary for t-PA: Relative Relative ContraindicationsContraindications

• Controversial–Evidence of a large MCA territory

infarction• Gray-white de-differentiation > 1/3 of

territory• Sulcal effacement/mass effect > 1/3 of

territory

Andrew Perron, MD

Future TrendsFuture Trends• MRI/MRA

• MR diffusion/perfusion/spectroscopy

• Transcranial doppler

• PET (Positron Emission) /SPECT (Single Photon Emission)

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Returning to our case…Diagnosis?Returning to our case…Diagnosis?

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Our CaseOur Case• Acute L MCA stroke (Loss of insular ribbon,

gray-white differentiation) No Blood…done?

Insular ribbon

Gray/white

Gray/White

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Our CaseOur Case

• Right frontal tumor with edema

Tumor

Edema

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Our CaseOur Case

• Thrombolysis witheld due to tumor

• Patient transferred to neurosurgical center

• Craniotomy yields diagnosis of astrocytoma

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Questions?Questions?