Acute Stroke Imaging

Radoslav Raychev, MD

UCI Stroke Center

Goals: • Determine stroke subtype • Understand mechanism • Institute treatment

Acute Stroke Facts • Leading cause of disability • 4rd leading cause of death in USA • 2nd leading cause of death worldwide • >5 million stroke survivors • $40 to $50 billion per year in the US • 1 in 6 Americans will be affected • 90% of those who survive will have deficits • 30% of strokes can be reversed • 80 % of strokes can be prevented

UCI Stroke Center

Stroke: Definition

Permanent injury to the brain or spinal cord of vascular origin (reduced blood flow or bleeding into or around the brain or spinal cord)

Stroke imaging objectives

• Brain tissue • Brain vessels

UCI Stroke Center

Brain Tissue Imaging - Non Contrast Head CT

ISCHEMIC

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Stroke Suspected

HEMORRHAGIC

Hemorrhagic stroke imaging

• Non-traumatic Intracerebral hemorrhage (ICH) = Intraparenchymal hemorrhage » 70% of intracranial hemorrhage

• Subarachnoid hemorrhage » 30% of intracranial hemorrhage

UCI Stroke Center

Head CT

• Advantages: » Quick » Best for bony anatomy » Excellent for blood » Widely available

• Disadvantages: » Radiation » Limited detail

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MRI for ICH

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Large draining vein

AVM nidus

Blood – dark on GRE weighted sequence

Gradient Echo Imaging – best for blood

UCI Stroke Center

GRE: Multiple microbleeds, not visible on other sequences

FLAIR

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Traumatic ICH » Epidural » Subdural » Intraprenchymal » Subarachnoid

• Mostly in the convexities

UCI Stroke Center

UCI Stroke Center

All Traumatic hemorrhages at once

Intraparenchymal Hemorrhage

• Cortical (lobar) • Deep (basal ganglia)

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Basal ganglia hemorrhage

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Basal ganglia = small vessel rupture usually due to chronic HTN

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Lobar hemorrhage - multiple etiologies

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Lobar hemorrhage = r/o vascular lesion

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VASCULAR LESIONS CAUSING ICH • AVM • DURAL AV FISTULA • CAVERNOUS MALFORMATION • VENOUS SINUS THROMBOSIS • ANEURYSM

• Mycotic • Blister • Dissecting

• VASCULITIS

VASCULAR IMAGING

CTA • Advantages

» Great spacial resolution • Aneurysms • Dissections • Stenosis

» Quick » Readily available

• Disadvantages » Radiation » Contrast

UCI Stroke Center

MRA • Advantages

» No contrast » No radiation » Special sequencing for arterial wall

• Dissection • Intraluminal clot

• Disadvantages » Less optimal spacial resolution » Prolonged acquisition » Motion artifact » Contraindicated in some implants

UCI Stroke Center

CTA MRA

Good for LARGE lesions

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Patient with posterior fossa ICH

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CTA - negative

Angiogram

• The “gold standard” vascular imaging • Most detailed • Dynamic • Invasive (0.5% risk of stroke) • Therapeutic

» The most advanced way to treat stroke

UCI Stroke Center

UCI Stroke Center

AVM

Tiny residual post embolization

Complete treatment with surgical resection

Vascular lesions requiring catheter angiogram

• AVM • Dural AV Fistula • Small (mycotic and “blister”) aneurysms

Vasculitis

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Dural AV Fistula

UCI Stroke Center

• 15 % of all cerebral vascular malformation » Direct high-flow communication between dural veins and

arteries » No intervening nidus (as opposed to AVM)

• Often missed on CTA or MRA • Leading to hemorrhage due to high venous pressure • Completely curable endovascularly

Artery

Vein

Patient with ICH and SAH

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CTA – negative

Cervical Dural AV fistula

Microcatheter in the fistula

No residual fistula after embolization with Onyx

Aneurysmal subarachnoid hemorrhage - facts

UCI Stroke Center

• 10-15% of patients die before reaching the hospital • 30-60% in-hospital mortality

• Lower at facilities with Interventional Neuroradiology Johnston S et al. Stroke. Jan 2000

• 80 % of survivors will have deficits • Better outcome with dedicated Neuro ICU team

Samuels et al, Neurocritcal Care 2001

Common location of cerebral aneurysms surrounding the circle of Willis.

•Meyers P M et al. Stroke 2009;40:e366-e379

• Copyright © American Heart Association

A, Middle cerebral (proximal to bifurcation, bifurcation, distal to bifurcation); (B) carotid terminus; (C) anterior choroidal; (D) superior hypophyseal; (E) anterior communicating (proximal to communicating artery, at communicating artery); (F) posterior communicating; (G) ophthalmic; (H) basilar artery (terminus, trunk); (I) superior cerebellar; (J) V4 segment, vertebral; (K) posterior inferior cerebellar; (L) pericallosal artery.

Aneurysmal subarachnoid hemorrhage - imaging

UCI Stroke Center

Blood is mostly in the cisterns and fissures, often accompanied by • Intraventricular Hemorrhage (IVH) • Hydrocephalus • Cerebral edema • Intraparechymal hemorrhage (IPH)

• Frontal lobe (A-comm) • Temporal lobe (MCA)

SAH FIISHER GRADING SCALE

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1 - No hemorrhage evident. 2 - SAH < 1mm thick 3 - SAH > 1mm thick 4 - SAH of any thickness with intra-ventricular hemorrhage (IVH) or parenchymal extension

ACA SAH pattern

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Blood in the interhemispheric fissure

Hematoma in the corpus callosum

IVH with hydrocephalus

Pericallosal Artery Aneurysm

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CTA

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ANGIO with coiling

Vasospasm after SAH

• Diagnostic » TCD – great screening and diagnostic tool » CTA or MRA – may be used for confirmation of

suspected vasospasm • Diagnostic and therapeutic

» Angiogram

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Vasospasm after SAH

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Vasospasm after SAH

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Ischemic Stroke Imaging

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The Ischemic Penumbra

Core Infarct

Ischemic Penumbra:

zone of salvageable tissue surrounding

core infarct

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In a typical acute ischemic stroke, every minute the brain loses

• 1.9 million neurons • 14 billion synapses • 7.5 miles myelinated fibers -- Saver, Stroke 2006

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Strategies in Acute Ischemic Stroke Therapy

• Proven » Recanalization » Supportive Care » Early Implementation of Secondary Prevention

• Experimental » Neuroprotection » Reperfusion via Collateral Enhancement

UCI Stroke Center

NINDS tPA Stroke Trials 1 and 2

tPA tPA Placebo Placebo

Excellent Recovery (mRS 0-1) Death

Hemorrhage p < .001

UCI Stroke Center

UCI Stroke Center

• Absolute imaging contraindication for IV TPA: »Evidence of intracranial hemorrhage

• In the first 3 hours virtually every patient has potentially salvageable tissue

Impact of Acute Ischemic Stroke Treatments

NNT Benefit per 100 pts TPA 1-3h 3 32 Thrombectomy (ICA/M1) 5 20 TPA 3-4.5h 6 16 IA Lytics 7 14 Stroke Unit 10 10 Aspirin 77 1 UCI Stroke Center

Ticking Clock Tissue Clock

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Bioenergetic Compromise

Hemodynamic Compromise

Occlusions or Stenoses

DWI PWI MRA

Tissue Status Perfusion Status Vessel Status

CBV CT PCT CTA

Multimodal CT

Multimodal MRI

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Non – contrast head CT

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Hyperdense vessel

No Evidence of early ischemic changes in the territory

Early ischemic changes

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• Effacement of the sulci • Obscuration between the gray/white matter junction

Completed infarct – frank hypodensity

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CT Perfusion Imaging

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Cerebral blood volume - for core Time to peak - for tissue at risk

Mismatch (penumbra) = Core / Tissue at risk

Vessel status – CTA

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No visible contrast in the L ICA

Collateral filling in the L MCA

MRI – best for acute stroke

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Diffusion weighted imaging (DWI) • Bright area = completed infarction • Identifies infarcted tissue within minutes of onset • The “gold standard” for visualization of core

DWI: Very tiny area of completed infarction GRE: No hemorrhage

Multimodal MRI

FLAIR: L ICA hyperintensity

PERFUSION: Large area of tissue at risk MRA: No flow in the L ICA

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FLAIR or T2 • best for subacute and old strokes

DWI FLAIR

MRI for acute stroke

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• Advantages: Most accurate evaluation of stroke size and location Detailed brain tissue evaluation

• Potential pitfalls: Time consuming Cost Contraindicated for some patients

Case # 1

• 65 y/o male with acute global aphasia and right sided hemiplegia (NIHSS 20)

• Presented to ED within 1 hour of onset • On full dose anticoagulation (contraindication

for IV TPA)

UCI Stroke Center

UCI Stroke Center

Hyperdense L MCA No early ischemic changes

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CTA Head – L M1 occlusion

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CTA Neck: - Severe R ICA stensosis - Complete L ICA occlusion

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Tiny channel within the occluded L ICA

• Catheter passed through the channel in the L ICA terminus • Injection through the catheter confirmed L MCA occlusion

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Complete reperfusion after one pass with the Solitaire Device

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L ICA remained occluded at the neck, but the L MCA was getting flow form the R ICA across the A-comm

Final Angiogram MRA the following day

Patient was walking and talking in full sentences within 24h (NIHSS = 2)

UCI Stroke Center

DWI sequence: Small area of infarcted tissue in the L frontal operculum

R ICA stenosis

Ulcerated plaque causing 80% stenosis

Successful CEA 2 weeks later

Case 2

• 50 y/o male with acute aphasia and R hemiplegia (NIHSS 22)

• Witnessed onset at work • 911 called • EMS transported the patient to primary stroke

center within 15 min (Riverside county)

UCI Stroke Center

Non – contrast head CT

UCI Stroke Center

• Patient received IV TPA • No improvement noted • Transferred to UCI • Arrived at UCI 4.5 hours after onset • Repeat exam showed persistent global

aphasia and R sided hemiplegia – NIHSS 22

UCI Stroke Center

UCI Stroke Center

Occluded L ICA Large Mismatch

• INR suite » within 60 minutes of CT completion

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Solitaire FR

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UCI Stroke Center

Follow up

• Substantial improvement within 24 hours: » Patient is moving the right side against gravity,

comprehends and utters simple words = NIHSS 10

UCI Stroke Center

UCI Stroke Center

Day 0 NIHSS 22

Day 5 NIHSS 10

CT CBV

MRI FLAIR

CTA

MRA

Acute Ischemic Stroke Care in the 21st Century

Symptoms Primary Stroke Center

EMS Call

Comprehensive Stroke Center EMS IV Lytic

IA Mechanical or Lytic Angiogram Stroke Unit

Multimodal Imaging

Imaging

Telemedicine

INR Cath Lab