NeuroimagingNeuroimaging of Strokeof Stroke

(Early signs on CT and MRI)(Early signs on CT and MRI)

IbrahimIbrahim AlmahbashiAlmahbashi, MD, MD

Assistant ProfessorAssistant Professor

Department of RadiologyDepartment of Radiology

SanaSana’’a Universitya University

IntroductionIntroduction

��Stroke is a leading cause of death and disability Stroke is a leading cause of death and disability worldwide.Theworldwide.The majority are majority are ischaemicischaemic in in originorigin..

��Intravenous or Intravenous or intraarterialintraarterial lysislysis are new are new therapeutic options for therapeutic options for ischaemicischaemic strokes.strokes.

��TheThe aimaim of of thisthis new new therapytherapy optionoption isis the the rapidrapidrestorationrestoration of of bloodblood toto hypoperfusedhypoperfused brainbraintissuetissue thatthat hashas notnot beenbeen irreversiblyirreversibly damageddamaged..

IntroductionIntroduction��StrictStrict selectionselection of of patientspatients benefitsbenefits fromfrom lysislysis

therapytherapy isis necessarynecessary, , otherwiseotherwise complicationscomplicationsmaymay occuroccur. .

��TimeTime window window forfor intravenousintravenous lysislysis therapytherapy isis 3 3 hourshours after after onsetonset of of symptomssymptoms((practicallypracticallydifficultdifficult))

��EffortEffort of of neuroumagingneuroumaging isis toto identifyidentify potentiallypotentiallysalvageablesalvageable brainbrain tissuetissue forfor the the aimaim of of extensionextensionof time window of time window forfor safesafe and and effectiveeffective treatment. treatment.

COMPUTED TOMOGRAPHYCOMPUTED TOMOGRAPHY

�� Noncontrast CT is the Noncontrast CT is the most important initial diagnostic most important initial diagnostic study in patients with acutestudy in patients with acute strokestroke..

�� The basic role is to exclude The basic role is to exclude primary inprimary inttracerebralracerebralhaemorrhagehaemorrhage. .

�� Exclusion of some clinically vague presented cases that Exclusion of some clinically vague presented cases that could resemble stroke as could resemble stroke as subdural hematomasubdural hematoma, , hemiplegic or hemisensory migrainehemiplegic or hemisensory migraine,, cerebritis cerebritis and and tumorstumors, ,

�� The sensitivity for The sensitivity for signssigns of ischemia on non contrast of ischemia on non contrast CT scans is within the range between 45% and 88% CT scans is within the range between 45% and 88% (mean 55.3%). (mean 55.3%).

Early signs of brain infarction on CTEarly signs of brain infarction on CT

��NormalNormal CT CT findingsfindings..

��HyperattenuatingHyperattenuating arteriesarteries..

��HypoattenuationHypoattenuation of grey matter structures:of grey matter structures:

��Insular ribbon signInsular ribbon sign

��Disappearing basal ganglia sign.Disappearing basal ganglia sign.

��MassMass effecteffect ..

HperattenuatingHperattenuating vessel signvessel sign

�� Indirect sign of acute infarction.Indirect sign of acute infarction.

�� Represents Stasis of flow due to Represents Stasis of flow due to intraluminalintraluminalthrombus or embolus, mostly seen in MCA.thrombus or embolus, mostly seen in MCA.

�� The most early sign!The most early sign!

�� First 90 min First 90 min -- 75%75%

�� 12 12 -- 24 hours 24 hours –– 15%15%

D/D/D:CalcifiedD:Calcified atherosclerosis(higheratherosclerosis(higherdensity,disappeardensity,disappear in follow up CT).in follow up CT).

HperattenuatingHperattenuating vessel signvessel sign

�� Proximal occlusion:Proximal occlusion:

M1 segment of MCAM1 segment of MCA

�� Distal occlusion:Distal occlusion:

M2, M3 segments of M2, M3 segments of

MCAMCA

Prognostic value of Prognostic value of HperattenuatingHperattenuating

vessel signvessel sign

�� It has been reported that proximal hyperdense vessel It has been reported that proximal hyperdense vessel sign is associated with poor shortsign is associated with poor short-- and longand long--term term prognosis in patients with ischemic strokeprognosis in patients with ischemic stroke(The patient (The patient either dead or dependent after 3 either dead or dependent after 3 monthesmonthes**).Intravenous ).Intravenous thrombolysisthrombolysis ineffectiveineffective

�� Patients with a distal hyperattenuating MCA signPatients with a distal hyperattenuating MCA sign does does not implicate poor outcome (not implicate poor outcome (independent in 64% of independent in 64% of casescases**).).Applicable to Applicable to thrombolyticthrombolytic therapytherapy

**Barber et al, Barber et al, Stroke 2001Stroke 2001

Proximal MCA Proximal MCA hyperdensehyperdense signsign

6 hrs

30 hrs

Proximal MCA Proximal MCA hyperdensehyperdense signsign

4hrs

72hrs

Distal MCA Distal MCA hyperdensehyperdense sign(dotsign(dot

sign)sign)

6hrs

32hrs

HyperdenseHyperdense PCA signPCA sign

�� HyperdensityHyperdensity within ambient cistern.within ambient cistern.

�� CT marker of acute CT marker of acute ischaemiaischaemia in territory of in territory of

PCA.PCA.

�� Could be Could be assciatedassciated with thalamic infarction.with thalamic infarction.

4hrs

24hrs

Insular ribbon signInsular ribbon sign

�� Normal stripe = Thin Normal stripe = Thin

white line (gray matter) white line (gray matter)

adjacent to darker gray adjacent to darker gray

line (line (subcorticalsubcortical white white

matter)matter)

�� With ischemiaWith ischemia

Insular stripe is lost due Insular stripe is lost due

to to cytotoxiccytotoxic oedemaoedema in in

grey matter loss of grey matter loss of

differentiationdifferentiation

claustrum

Island of Reil

Insular ribbon signInsular ribbon sign

Insular ribbon signInsular ribbon sign

Insular strokeInsular stroke

�� Minor insular strokeMinor insular stroke

<2/3 of <2/3 of insulainsula involved.involved.

�� Major insular strokeMajor insular stroke

>2/3 of >2/3 of insulainsula involved, usually with other involved, usually with other

MCA territories.MCA territories.

CytotoxicCytotoxic oedemaoedema & & hypodensityhypodensity on CTon CT

�� Increase in tissue water Increase in tissue water

content by 1%content by 1%

→→ 2,5 HU decrease in 2,5 HU decrease in

parenchymalparenchymal

AttenuationAttenuation

�� Mean attenuation decrease in Mean attenuation decrease in

MCA stroke MCA stroke

50.0 50.0 →→ 48.4 HU 1 hour 48.4 HU 1 hour

50.0 50.0 →→ 42.5 HU 4 hours42.5 HU 4 hours

4hrs

48hrs

Loss of basal ganglia differentiationLoss of basal ganglia differentiation

�� Due to occlusion of Due to occlusion of

M1 segment of MCA M1 segment of MCA

proximal to proximal to

lenticulostriatelenticulostriate

arteries.arteries.

�� Good adjustment of Good adjustment of

CT window setting is CT window setting is

necessary(w:80,C:35) necessary(w:80,C:35)

Mass effectMass effect

Early mass effect Early mass effect

includes effacement includes effacement

of of sulccisulcci and and

narrowing of narrowing of SylvianSylvian

fissure.fissure.

MRIMRI

Protocol:Protocol:

�� Conventional sequences as T1WI&T2WI have Conventional sequences as T1WI&T2WI have

no advantages over CT in the diagnosis of no advantages over CT in the diagnosis of

hyperacutehyperacute stroke.stroke.

�� FLAIR is more sensitive.FLAIR is more sensitive.

�� DWI.DWI.

�� PWI.PWI.

�� MRA.MRA.

DWIDWI

�� DWI can detects stroke in early acute stages of DWI can detects stroke in early acute stages of

stroke (0 stroke (0 -- 6 hours after onset of symptoms).6 hours after onset of symptoms).

�� Cellular energy failure leads to loss of ion Cellular energy failure leads to loss of ion

homeostasis and homeostasis and cytoxiccytoxic edemaedema, i.e., more , i.e., more

intracellular water, less intracellular water, less extracellularextracellular water; water water; water

(protons) have more restricted diffusion (protons) have more restricted diffusion

intracellularlyintracellularly than than extracellularextracellular

hyperintensehyperintense signalsignal

DWIDWI

�� High signal on DWI does not necessarily mean High signal on DWI does not necessarily mean

acute lesion since DWI is affected by T2 effects acute lesion since DWI is affected by T2 effects

of of vasogenicvasogenic edema in chronic infarcts ("T2 edema in chronic infarcts ("T2

shineshine--through").through").

�� Rapid sequence, less Rapid sequence, less atrifactatrifact..

�� Should be correlated with Should be correlated with ADCADC

DWI SEEN ALSO INDWI SEEN ALSO IN

�� Status Status epilepticusepilepticus induced by barbiturate, induced by barbiturate,

�� Severe hypoglycemia Severe hypoglycemia

�� Venous Venous thromobosisthromobosis, , eclampsiaeclampsia ((incr.ADCincr.ADC with with

vasogenicvasogenic edema). edema).

�� DWI and PWI together are quite specific for DWI and PWI together are quite specific for

ischemiaischemia

T2 DWI ADC

DWI&ADCDWI&ADC

PWIPWI

�� Important to detect the Important to detect the penumbrapenumbra

�� Usually correlated with DWI(PWI/DWI)Usually correlated with DWI(PWI/DWI)

�� If PWI/DWI mismatch>25% patient If PWI/DWI mismatch>25% patient

applicable to applicable to thrombolyticthrombolytic therapytherapy**

Steven R et alSteven R et al ,Stroke 2007,Stroke 2007

DWIDWI

PWIPWI

MRAMRA

DWIDWI

PWIPWI

MRAMRA

DWIDWI

LacunarLacunar infarctionsinfarctions

�� About 25% of all strokes.About 25% of all strokes.

�� Frequently found in basal ganglia, internal Frequently found in basal ganglia, internal

capsule, thalamus and capsule, thalamus and ponspons..

�� Usually not recognized in acute stage on CT due Usually not recognized in acute stage on CT due

to their small size.to their small size.

�� D/D/D:dilatedD:dilated perivascularperivascular VirchowVirchow--Robin spaces.Robin spaces.

LacnarLacnar infarctionsinfarctions

Venous infarctionVenous infarction

�� High High pospartumpospartum incidence, trauma, dehydration incidence, trauma, dehydration

,,pyogenicpyogenic infection,..infection,..

�� Clinically:headachClinically:headach, nausea, neurological , nausea, neurological

deterioration, seizures.deterioration, seizures.

�� May affect large sinus or small deep veins.May affect large sinus or small deep veins.

�� Infarctions usually Infarctions usually bilateral,parasagittalbilateral,parasagittal and and

often often haemorrhagichaemorrhagic..

Venous infarctionVenous infarction

��NECTNECT: :

�� Cord sign of Cord sign of

superficial cerebral superficial cerebral

vein.vein.

Venous infarction cont.Venous infarction cont.

��NECTNECT

�� CorticalCortical or or subcorticalsubcortical

hypodensityhypodensity((usuallyusually

bilateralbilateral).).

Venous infarction cont.Venous infarction cont.

��NECTNECT

�� CorticalCortical or or subcorticalsubcortical

hyperdensityhyperdensity, , ifif

haemorrhagichaemorrhagic, ,

((usuallyusually bilateralbilateral).).

Venous infarction cont.Venous infarction cont.

��CECTCECT: :

EmptyEmpty delta delta signsign..

Venous infarctionVenous infarction

�� MRIMRI

�� Loss of the normal signal void within the Loss of the normal signal void within the thrombosedthrombosed

sinus in T2WI, replaced by sinus in T2WI, replaced by hyperintensityhyperintensity that that

represents the thrombus.represents the thrombus.

�� HypointensityHypointensity in T1WI and in T1WI and hyperintensityhyperintensity in T2WI in in T2WI in

cortical or cortical or subcorticalsubcortical areas in cases of pure infarction.areas in cases of pure infarction.

�� In cases of In cases of haemorrhagehaemorrhage the signals depend on the age the signals depend on the age

of of haematomahaematoma. .

Venous infarction MRIVenous infarction MRI

MRVMRV

CONCLUSIONCONCLUSION

�� CT scan is the standard of care in acute stroke CT scan is the standard of care in acute stroke imaging.Itimaging.It is is widely available, fast and practical.widely available, fast and practical.

�� Early CT signs of stroke are of therapeutic and prognostic valueEarly CT signs of stroke are of therapeutic and prognostic valueand can indicate specific arterial occlusion.and can indicate specific arterial occlusion.

�� DWI in MRI is more sensitive in the DWI in MRI is more sensitive in the hyperacutehyperacute stage of stroke stage of stroke but should be used with ADC.but should be used with ADC.

�� MRI is also better in clarifying MRI is also better in clarifying cerebellarcerebellar and brain stem and brain stem infarctions.infarctions.

�� PWI/DWI mismatch on MRI can select patient for PWI/DWI mismatch on MRI can select patient for thrombolysisthrombolysistherapy beyond currently known time window.therapy beyond currently known time window.

Brain imaging can reduce health cost if it prevents Brain imaging can reduce health cost if it prevents

the disability and death of stroke victims.the disability and death of stroke victims.

Thank youThank you