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Craniocervical  Arterial Dissection: Spectrum of Imaging Craniocervical  Arterial Dissection: Spectrum of Imaging

Craniocervical Arterial Dissection: Spectrum of Imaging - PowerPoint Presentation

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Craniocervical Arterial Dissection: Spectrum of Imaging - PPT Presentation

Findings Radiographics 2008 EKhalili Pouya Causal Factors traumatic severe blunt head and neck trauma spontaneous coughing vomiting sports cervical manipulationtrigger in ID: 917604

hematoma dissection vertebral angiography dissection hematoma angiography vertebral artery ica intramural image sign axial shows weighted lumen thickening contrast

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Slide1

Craniocervical Arterial Dissection: Spectrum of Imaging Findings

Radiographics

2008

E.Khalili

Pouya

Slide2

Causal Factors:traumatic

(severe

blunt head and neck

trauma)

spontaneous (coughing, vomiting, sports, cervical

manipulation),trigger in

pts

with underlying

arteriopathy

(FMD, Ehlers

Danlos

IV

,

Marfan

syndrome, autosomal dominant polycystic kidney disease, and

osteogenesis

imperfecta

type

I

Slide3

Anatomic Distribution:The extracranial

segments of the carotid and vertebral arteries are much more likely to undergo dissection than their intracranial

segments

Extracranial

ICA dissection affects the cervical part of the artery distal to the carotid bulb and tends not to extend beyond its entry into the petrous portion

Slide4

Slide5

Slide6

segments of the vertebral artery. V1 = between its origin and its entry into the transverse foramen of the C6 vertebra, V2 =

midcervical

course between the processes of C6 to C2, V3 = atlas loop region, V4 = intracranial segment. Note the asymmetric venous plexus enhancement around the V3 segment (arrow in a).

Slide7

Color Duplex US:linear transducers (4–8 MHz).

Mural hematoma and thrombus may be detected as a thickened

hypoechoic

vessel

wall

Usually, wall hematoma and intraluminal thrombus cannot be differentiated with B-mode

imaginginner intimal echo helps in distinguishing wall hematoma from intraluminal thrombus or plaque in patients with thickening of the ICA wall

Slide8

Slide9

Slide10

Slide11

CT Angiography:Unenhanced

brain CT is helpful to document associated ischemic and hemorrhagic

events

scanning range from the aortic arch to the circle of

Willis

section thickness of 0.625

mm pitch of

0.9

80

mL of nonionic contrast medium (iodine, 350 mg/mL) followed by a saline bolus at a rate of 3.5 mL/sec.

Slide12

ICA dissection is characterized by a narrow eccentric lumen with increase of the external diameter of the

artery

At unenhanced brain CT, a spontaneous crescent-shaped

hyperattenuating

area corresponding to a wall hematoma may be noticed in acute dissection at the upper portion of the cervical ICA. However, when correct window settings are applied for CT angiography, intramural hematoma appears

isoattenuating

to the surrounding muscles and cannot be differentiated from atherosclerotic thickening or thrombus Thus, familiarity with common dissection sites is essential to diagnose ICA dissection with CT angiography.

Slide13

The typical target picture (narrow eccentric lumen surrounded by crescent-shaped mural thickening and thin annular enhancement) is a very specific yet less sensitive sign of arterial dissection

Peripheral enhancement is probably due to the contrast enhancement of the vasa

vasorum

in the adventitial layer

Other fairly reliable signs of arterial dissection are an intimal flap, a dissecting

aneurysm

Slide14

Slide15

Axial image from CT angiography obtained with the same window settings does not show any parietal abnormality.

Slide16

On an axial image from CT angiography obtained with wide window settings (width = 500 HU, level = 100 HU), the intramural wall hematoma (arrow) is

isoattenuating

relative to the surrounding muscles and cannot be differentiated from atherosclerotic thickening.

Slide17

Axial unenhanced brain CT image shows a crescent-shaped

hyperattenuating

area (arrow), which corresponds to an intramural hematoma in the right ICA.

Slide18

Axial image from CT angiography shows the residual lumen (arrowhead)

Slide19

Slide20

Slide21

Volume-rendered image from CT angiography shows a long tapered stenosis that begins distal to the carotid bulb (the string sign)

Slide22

Slide23

Slide24

Vertebral Artery Dissection:Increased external diameter and crescent-shaped mural

thickening

both signs can be found in

nondissected

vertebral

arteries

typical target sign was also demonstrated intimal flap is less frequent than an intramural hematoma

Slide25

Slide26

Slide27

Axial image shows intracranial extension of the dissection with crescent-shaped parietal thickening of the left V4 vertebral artery (arrow).

Slide28

Slide29

Potential Pitfalls: source images and reformatted 2D and 3D images from CT angiography can be affected by bone artifacts at the skull base and by dental artifacts

Slide30

Slide31

MR Imaging and MR Angiography:Time-of-flight (TOF) MR angiography can also demonstrate

subacute

intramural

hematoma

phase-contrast MR angiography and contrast-enhanced MR angiography demonstrate only the vessel

lumen

TOF MR angiography and contrast-enhanced MR angiography are commonly used to evaluate the intracranial and extracranial vessels, whereas experience with phase-contrast MR angiography is limited in carotid and vertebral artery dissection.

Slide32

The hematoma shows a typical evolution of signal intensity related to the paramagnetic effects of the products of hemoglobin breakdown

.In

the early and chronic stage, the hematoma is usually

isointense

to surrounding structures, whereas between 7 days and 2 months it is almost invariably bright on T1-weighted images

.Acute

dissection can hardly be detected on T1-weighted images with fat saturation because isointense hematoma may be obscured when surrounded by isointense tissues.

Slide33

The hematoma usually becomes isointense within 6 months or disappears

Subacute

hematoma is more clearly visualized on T1-weighted images with fat saturation and appears characteristically as a crescent-shaped

hyperintense

area around an eccentric flow void corresponding to the vessel lumen

Slide34

Axial T1-weighted MR image shows

isointense

wall thickening of the right ICA (arrowheads), a finding consistent with an acute intramural hematoma (

oxyhemoglobin

or

deoxyhemoglobin

phase

Slide35

fat-saturated T1-weighted MR image obtained in another patient shows slightly

hyperintense

wall thickening of the left ICA (arrowheads), a finding consistent with an early

subacute

intramural hematoma (

methemoglobin

phase).

Slide36

Axial T1-weighted MR images obtained with fat saturation (a obtained at a higher level than b) show a narrowed eccentric flow void (arrowhead) surrounded by a crescent-shaped circumferential

subacute

intramural hematoma that expands the vessel diameter. The hematoma spirals around the

vessel lumen

.

Slide37

The criteria used for dissection are:increase

in the external diameter of the artery and narrowing of the lumen.

flow

void narrowing is a less useful indicator of dissection because it can be encountered in other conditions.

train track” sign, a sign of

poststenotic laminar flow in the petrosal

horizontal portion of the ICA, can be mistaken for

intrapetrous

extension of ICA dissection

.

Increase

in the external diameter of the artery may be present in cases of dissecting aneurysm

Slide38

MR imaging is not as helpful in diagnosis of vertebral artery dissection Dissection at V2 may be difficult to identify because inflow enhancement in the venous plexus of the foramen

transversarium

may mimic

subacute

hematoma

Another problem with diagnosis of vertebral artery dissection is the common exclusion of V1 from the imaged volume MR imaging demonstrated excellent sensitivity in diagnosis of internal carotid dissection

Slide39

Axial

T1-weighted MR image obtained with fat saturation shows

hyperintense

crescent-shaped mural thickening, a finding consistent with a

subacute

intramural hematoma. Note the intermediate signal intensity of the venous plexus around the left vertebral artery and in the anterior epidural space.

Slide40

Three-dimensional TOF MR image shows

pseudoenlargement

of the lumen due to a

subacute

intramural hematoma (arrowhead).

Slide41

Axial

diffusion-weighted MR image demonstrates the

hyperintense

subacute

intramural hematoma (arrowhead) owing to the T2 “shine-through” effect.

Slide42

contrast-enhanced MR angiography of the cervical vasculature occasionally results in segmental blurring or signal intensity loss within the vertebral arteries, especially in young patients with rapid circulation

times

This “feathering” artifact results from rapidly changing signal intensity in small vascular structures around the vertebral arteries

This

pseudostenosis

artifact may mimic vertebral artery dissection

Slide43

Our protocol for craniocervical arterial dissections

:

cross-sectional

T1-weighted

+

fat saturation of the neck

contrast-enhanced MR angiography.Additional axial T1- and T2-weighted images may be required in cases of acute dissections.

nonenhanced

MR angiography when gadolinium-containing contrast agents are contraindicated.

Slide44

Digital Subtraction Angiography: string sign, the angiographic hallmark of ICA dissection, is a long, tapered, usually eccentric and irregular stenosis that begins distal to the carotid bulb

Focal narrowing with a distal site of dilatation is referred to as the “string and pearl”

sign

Pathognomonic signs, such as a double lumen or intimal flap, are rarely observed

“flame” sign, a tapered occlusion that spares the carotid bulb, is highly suggestive of dissection

Slide45

Angiogram shows the string sign (thin arrow) and the “string and pearl” sign (thick arrow), findings consistent with bilateral ICA dissections. Note the “string of beads” sign (arrowhead), which is consistent with

fibromuscular

dysplasia of the left vertebral artery.