Border Zone Infarcts

BorderZoneInfarctsClassiicationofBorderZoneInfarcts•Watershedsorborderzonesareareasthatlieatthejunctionoftwodifferentdrainageareas.Thevascularsupplyofthecerebralparenchymacanbeenvisionedinasimilarmanner,withdeinedboundariesbetweendifferentarterialsystems.•Cerebralinfarctsinborderzoneswereirstdiscussedin1883•Followingthe1940sand1950s,ZulchandBehrendreportedthetypicaltopographicalareasofBZIandhypothesisedtheirhaemodynamicmechanism.•BZIsarefrequent,accountingforabout10%ofallbraininfarcts.Dateofdownload:6/29/2012Copyright©2012AmericanMedicalAssociation.Allrightsreserved.From:WatershedInfarctionsAreMoreProneThanOtherCorticalInfarctstoCauseEarly-OnsetSeizuresArchNeurol.2010;67(10):1219-1223.doi:10.1001/archneurol.2010.263Cerebralmagneticresonanceimagesof14patientswithcerebralinfarct–relatedearlyseizures.Patientswerenumberedintheordertheywereadmittedtothestrokeunit.Asterisksindicatepatientswithwatershedinfarcts.FigureLegend:ExternalBorderZoneInfarcts•Figure1.ColoroverlaysonaxialT2-weightedmagneticresonance(MR)imagesofnormalcerebrumshowprobablelocationsofexternal(blue)andinternal(red)borderzoneinfarcts.•Isolatedcorticalborderzoneinfarctsmaybeembolicinnatureandarelessfrequentlyassociatedwithhemodynamiccompromise.InternalBorderZoneInfarcts•Incontrasttoexternalborderzoneinfarcts,internalborderzoneinfarctsarecausedmainlybyarterialstenosisorocclusion,orhemodynamiccompromise(Fig3).HypereosinophiliaandBorderZoneInfarcts•Figure6.Axialdiffusion-weightedMRimagesob-tainedina26-year-oldmanwithasuddenonsetofencephalopathyshowmultiplesmallabnormalregionswithhyperintensesignaldistributedinvascularwatershedterritories.Idiopathichypereosinophilicsyndromewassubsequentlydiagnosed.Rightdeepborderzonecerebellarinfarctwithipsilateralproximallargearterydisease•Axial(A)diffusion-weightedimagingdisplaysacutedeepinfarctattheboundaryzonebetweenmedialandlateralbranchoftherightposteriorinferiorcerebellarartery.Anterior(B)andlateral(C)viewsofCTangiographyshowocclusionofrightvertebralarteryandstenosisofrightsubclavianartery(arrows).Bilateralinternalsuperiorcerebellararterywatershedinfarction•Thus,thetypicallysmallinternalborderzoneinfarctsrepresentthe“tipoftheiceberg”Infarctsofdecreasedperfusionreserveandmaybepredictiveofimpendingstroke.RoleofNeuroimagingFigure9.Decreasedcerebrovascularreserveinapatientwithaninternalborderzoneinfarct.(a)AxialT2-weightedluid-attenuatedinversionrecoveryimageshowsmultipleareasofhyperintensesignalintheleftcoronaradiata.(b)CerebralbloodlowmapobtainedatCTbeforetheadministrationofacetazolamideshowsslightlydecreasedperfusionintheleftcerebralhemisphere.(c)CerebralbloodlowmapobtainedatCTaftertheadministrationofacetazolamide(samelevelasb)showsreducedcerebralbloodlowincorticalareasoftheleftcerebralhemisphereandincreasedlowinthenormalrightcerebralhemisphereincomparisonwithb.Conclusions•Internal(subcortical)borderzoneinfarcts,whichtypicallyappearinalinearrosarylikepatterninthecentrumsemiovale,arecausedmainlybyhemodynamiccompromise.•External(cortical)borderzoneinfarctsarebelievedtobecausedbyembolism,sometimeswithassociatedhypoperfusion.Externalborderzoneinfarctsusuallyfollowabenignclinicalcourse,whereasinternalborderzoneinfarctsareassociatedwithhighermorbidityandahigherriskforfuturestroke.Conclusions•Differenttherapeuticapproachesmayberequiredtopreventearlyclinicaldeteriorationinpatientswithdifferenttypesofborderzoneinfarcts.•AdvancedimagingtechniquessuchasdiffusionandperfusionMRimaging,PET,perfusionCT,andtranscranialDopplerUScanbehelpfulforunderstandingthepathophysiologyoftheseinfarcts,detectingassociatedhemodynamiccompromise,andguidingdiseasemanagement.