[PPT] - Imaging Modalities in Acute Stroke: Time is Brain Jeremiah Scharf, PowerPoint Presentation

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Jeremiah Scharf Gillian Lieberman, MD

Imaging Modalities in Acute Stroke:

Jeremiah Scharf, Harvard Medical School, MS IV Gillian Lieberman, MD Beth Israel-Deaconess Medical Center Department of Radiology

April 2001

Time is Brain

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2 Jeremiah Scharf Gillian Lieberman, MD

Stroke - Definition and Statistics

Acute, vascular injury to CNS

<24 hrs = TIA >24 hrs = stroke (CVA)

Affects 600,000 people/ yr

(that is 1 stroke per minute!)

Is #3 cause of mortality in adults Is #1 cause of disability

http://www.swmed.edu/stars/resources/stroke.html

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3 Jeremiah Scharf Gillian Lieberman, MD

Types of Stroke

Hemorrhagic (20%)

usually hypertensive hemorrhage

Ischemic (80%)

Thrombotic (40%)

intracerebral atherosclerosis

Embolic (60%)

Cardiac embolus (thrombus, tumor, septic embolus) artery-to-artery (mainly carotid thrombus) Paradoxical embolus (thrombus, fat, air)

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4 Jeremiah Scharf Gillian Lieberman, MD

Risk Factors for Stroke

Atherosclerosis risk factors

Family history of CVA, TIA, or MI Hypertension Smoking Diabetes Hypercholesterolemia

Previous CVA, TIA, or MI Atrial fibrillation

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5 Jeremiah Scharf Gillian Lieberman, MD

Our Patient - BF

86 yo F w/ Hx of HTN, CAD s/p MI,

and high cholesterol

presented to PCP for routine visit Felt “funny” -> began seizing In ED, unresponsive, L. sided hemiplegia

eyes deviated to the right

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6 Jeremiah Scharf Gillian Lieberman, MD

Differential Diagnosis

Many CNS diseases can mimic ischemic

stroke

Hemorrhage Mass lesion (tumor, abscess, AVM) Seizure (Todd’s paralysis) Hemiplegic migraine MS flare Venous infarct

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7 Jeremiah Scharf Gillian Lieberman, MD

Goals of Imaging in Acute Stroke

1. Rule in or out other disease processes
2. Define location, extent and age of infarct
3. Do so as rapidly as possible

TIME IS BRAIN

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Cerebrovascular Anatomy

MGH Handbook of Neurology

Posterior Circulation Anterior Circulation

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9 Jeremiah Scharf Gillian Lieberman, MD

Anatomy of the Anterior Circulation

High Yield Neuroscience

Internal carotid artery Anterior cerebral artery Middle cerebral artery Middle cerebral artery Internal carotid artery Anterior cerebral artery

MGH Handbook of Neurology

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Vascular territories in the brain

MGH Handbook of Neurology

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11 Jeremiah Scharf Gillian Lieberman, MD

Imaging Modalities in Acute Stroke

CT without contrast Conventional MRI Diffusion-Weighted and Perfusion MRI MRA Ultrasound

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12 Jeremiah Scharf Gillian Lieberman, MD

CT Imaging in Acute Stroke - 1

Initial test of choice Best modality for

detecting hemorrhage

Identifies mass lesions

(tumor, abscess, AVM)

Fast and readily available

= Crucial for stroke triage

BIDMC

Patient #2 - LL

(rule in/out other diseases)

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13 Jeremiah Scharf Gillian Lieberman, MD

CT Imaging in Acute Stroke - 2

BIDMC

HOWEVER,

CT is poor at detecting acute

infarcts

Only 40% sensitivity <24 h

Film Findings for our patient, BF: Normal Initial Head CT

Patient #1 – BF; 1-2 hrs post stroke

2 hours post stroke

Our Patient

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14 Jeremiah Scharf Gillian Lieberman, MD

Our patient BF: CT#2 – 8 hours later

As time passes, classic

signs of stroke appear:

Patient #1 – BF; 8 hrs post stroke

BIDMC

Loss of gray-white matter differentiation Sulcal effacement

Normal sulci Normal G/W diff.

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Our patient BF CT#3 - 2 days later

Patient #1 – BF; 48 hrs post stroke

BIDMC

Complete loss of gray-white matter differentiation Sulcal effacement ? hemorrhagic transformation

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Therefore, other imaging modalities are used to detect strokes < 6 hours!

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CT without contrast Conventional MRI Diffusion-Weighted and Perfusion MRI MRA Ultrasound

Imaging Modalities in Acute Stroke

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18 Jeremiah Scharf Gillian Lieberman, MD

Conventional MR Imaging in Stroke

Slight incr. detection rate

ver CT in early stroke

T2 hyperintensity visible

at 12-24 hrs (80% +)

represents edema May see absent flow voids

= arterial occlusion T1 imaging basics T2 imaging basics

BIDMC BIDMC

CSF is dark Soft tissue is bright Good for mass lesions CSF is bright Soft tissue is dark Good for edema (bright) T1 T2

Our Patient

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19 Jeremiah Scharf Gillian Lieberman, MD

Conventional MR Imaging in Stroke

Our patient, BF, underwent an

MRI study immediately following her initial CT, 2 hours after her stroke

T2 image

BIDMC

Patient BF; 2 hrs post stroke

Normal Initial MRI: ? Absent R. MCA Flow Void (suggestive of MCA occlusion) Film Findings:

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Our patient BF - MRI #2 :30 hours later

BIDMC

At 30 hrs., classic MR signs

f infarct are present

Patient BF; 30 hrs post stroke

T2 hyperintensity in temporal lobe, MCA distribution Film Findings: T2 image

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Conclusions - Conventional MR Imaging in Acute Stroke

Conventional MRI can detect acute infarcts

slightly earlier than CT

Nonetheless, additional techniques are still

needed for early stroke detection

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22 Jeremiah Scharf Gillian Lieberman, MD

Imaging Modalities in Acute Stroke

CT without contrast Conventional MRI Diffusion-Weighted and Perfusion MRI MRA Ultrasound

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Diffusion Weighted MRI Imaging (DWI)

Osmotic pump failure is 1st event in

ischemia

Fluid shift extracellular->intracellular Water in cells now can’t diffuse! Detected as decreased diffusion

coefficient (ADC)

Increased restriction of diffusion

(DWI)

Detects change within 30 minutes

f onset of stroke

Beats T2 signal by 3-6 hours !!!

Schaefer et al. Radiology 217:331-345, 2000

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Our Patient had a DWI MRI immediately following the initial routine MRI

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25 Jeremiah Scharf Gillian Lieberman, MD

In our patient, DWI

sequences were performed during her initial MRI

A faint increase in DWI

signal was observed in the temporal and insular cortex.

Indicated early ischemia in

MCA territory

Led to treatment with IV

thrombolytic therapy (t-PA)

BIDMC

Patient BF; 2 hrs post stroke

DWI in BF at 2 hours post-stroke

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That’s good, but could we predict how bad her stroke might get?

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27 Jeremiah Scharf Gillian Lieberman, MD

Imaging the Penumbra: the Holy Grail of Stroke Diagnostics

DWI is thought to show the area

currently infarcting.

But is there an “area at risk”

where blood flow is reduced but cells haven’t died yet?

Imaging this region (the penumbra)

= goal of MR perfusion imaging

Uses gadolinium for contrast Changes magnetic properties of

perfused tissue vs. non-perfused

Measures decreased flow in

penumbra!

increased mean-transit-time

(MTT) of blood flow to penumbra

http://www.swmed.edu/stars/resources/stroke.html

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Correlation of Perfusion Imaging with Infarct Progression

Baird AE and Warach S. J. Cereb. Blood Flow Metab. 18(6): 583-609, 1998.

= area of low/ slow blood flow = area at risk for stroke extension

DWI

Late (29h): =larger area

f injury

(correlates w/ 2h MTT)

MTT

Early (2h): =small area

f injury

territory (complete)

R. MCA

territory

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43 Jeremiah Scharf Gillian Lieberman, MD

Imaging Modalities in Acute Stroke

CT without contrast Conventional MRI Diffusion-Weighted and Perfusion MRI MRA Ultrasound

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44 Jeremiah Scharf Gillian Lieberman, MD

MRA/Angiography of occluded MCA

Bahn et al. JMRI 6:833-845, 1996 BIDMC BIDMC

Patient BF; R. MCA occlusion Patient BF; R. MCA occlusion

L. MCA occlusion -literature
ur patient – R. MCA
ur patient – R. MCA

companion patient –L. MCA

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45 Jeremiah Scharf Gillian Lieberman, MD

Imaging Modalities in Acute Stroke

CT without contrast Conventional MRI Diffusion-Weighted and Perfusion MRI MRA Ultrasound

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46 Jeremiah Scharf Gillian Lieberman, MD

Ultrasound in Stroke

Has a primary role in working up cause of stroke Echocardiography

TEE for LA/LV thrombus Bubble echo study for PFO (paradoxical embolus)

Carotid Ultrasound

Evaluates patency of carotids and degree of stenosis

Transcranial Doppler Ultrasound

Evaluates patency of intracranial arteries (MCA)

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47 Jeremiah Scharf Gillian Lieberman, MD

Summary I – Patient Course

BF was given t-PA within 3 hours of onset

30% increase in recovery over controls

(31% t-PA vs. 20% placebo = minimal/ no disability @ 3 mos.)

6-fold increased risk of bleeding (6% vs. 1%?)

Symptoms of stroke did not improve considerably Intubated in ICU for 1 week Transferred to floor with residual weakness Discharged to rehabilitation facility after 10 days

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Summary II – Timing of stroke detection in our patient

CT without contrast Conventional MRI DWI MRI MRA Imaging Modality Time of post-stroke imaging 2h 8h 30h

+

+

ND

+

ND

+ + +

ND

+

+ = evidence of acute stroke; - = no evidence of acute stroke; ND = not determined

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Summary III – Imaging in Stroke

Acute Stroke (<6 hours)

CT (without contrast!!)

Excellent for ruling out hemorrhage, other diseases Poor in defining early infarcts

Conventional MRI (T1,T2)

Bad for hemorrhage, fair for early infarcts

Diffusion-Weighted and Perfusion MRI

Excellent for defining early infarcts (1-2 hrs)

and for estimating areas at risk

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Summary IV - Imaging in Stroke

Sub-acute Stroke (>6 hours)

CT (without contrast)

Excellent in defining late infarcts (>24 h)

sulcal effacement, loss of gray-white differentiation

Conventional MRI (T1,T2)

Better than CT at 6-24h; Same as CT in infarcts > 24h

T2 hyperintensity is most indicative of injury

Ultrasound

Critical for workup of origin of stroke (TEE, TCD,

Carotid Doppler)

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Summary V - Imaging in Stroke

In the near future, there will hopefully be effective

treatments for acute stroke.

Patients will need to come to the ER at first sign

f “brain attack”.

Patients will need to be imaged by multiple

modalities rapidly.

Remember ...

TIME IS BRAIN

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References

AHA Website: http://www.americanheart.org/statistics/stroke.html Bahn MM, Oser AB, Cross DT. CT and MRI of Stroke. JMRI 6:833-845, 1996. Baird AE and Warach S. Magnetic Resonance Imaging in Acute Stroke. J. Cereb. Blood Flow Metab. 18(6): 583-609, 1998. Beauchamp NJ, Barker PB, Yang PY, vanZijl PCM. Imaging of Acute Cerebral Ischemia. Radiology 212:307-324, 1999. Culebras A et al. AHA Scientific Statement: Practice Guidelines for the Use of Imaging in Transient Ischemic Attacks and Acute Stroke. Stroke. 28:1480-1497, 1997. Flaherty AW. MGH Handbook of Neurology. Lippincott Williams and Wilkins 2000. Fix J. High-Yield Anatomy. Lippincott Williams & Wilkins. Philadelphia. 2000. Lev MH, Farkas J, Gemmete JJ, Hossain ST, Hunter GJ, Kroshetz WJ, Gonzalez RG. Acute Stroke: Improved Nonenhanced CT Detection – Benefits of Soft-Copy Interpretation by Using Variable Window Width and Center Level Settings. Radiology 213: 150-155, 1999. Petrella JR and Provenzale JM. MR Perfusion Imaging of the Brain. AJR 175:207-219, 2000. Schaefer PW, Grant PE, Gonzalez RG. Diffusion Weighted MR Imaging of the Brain. Radiology 217:331-345, 2000 Simon RP, Aminoff MJ, Greenberg DA. Clinical Neurology. Appleton & Lange: Connecticut, 1999. UT Southwestern STARS Website: http://www.swmed.edu/stars/resources/stroke.html

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Acknowledgments

Andru Bageac and Daniel Saurborn

for help with case identification

Beverlee Turner

for help with Power point and PACS

Gillian Lieberman

for her enthusiasm in teaching medical students

My classmates

for enduring this talk