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Trauma Section 1

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TraumaOverview

Trauma is one of the most frequent indications for emergent neuroimaging. Because imaging plays such a key role in patient triage and management, we begin this book by discussing skull and brain trauma.

Westartwithabriefconsiderationofepidemiology.Traumaticbraininjury (TBI)isacriticalpublichealthandsocio-economicproblemthroughoutthe world.Thedirectmedicalcostsofcaringforacutelytraumatizedpatientsare huge.Theindirectcostsoflostproductivityandlong-termcareforTBI survivorsareevenlargerthantheshort-termdirectcosts.

Wethenbrieflydiscusstheetiologyandmechanismsofheadtrauma. Understandingthedifferentwaysinwhichtheskullandbraincanbeinjured providesthecontextforunderstandingthespectrumoffindingsthatcanbe identifiedonimagingstudies.

Introduction

EpidemiologyofHeadTrauma

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Trauma—sometimescalledthe"silentepidemic"—isthemostcommon worldwidecauseofdeathinchildrenandyoungadults.Neurotraumais responsibleforthevastmajorityofthesecases.Atleast10millionpeople worldwidesustainTBIeachyear.IntheUSAalone,twomillionpeople annuallysufferaTBI.Ofthese,500,000requirehospitalcare.

Ofallhead-injuredpatients,approximately10%sustainfatalbraininjury. Lifelongdisabilityiscommoninthosewhosurvive.Between5-10%ofTBI survivorshaveseriouspermanentneurologicdeficits,andanadditional2040%havemoderatedisability.Evenmorehavesubtledeficits("minimalbrain trauma").

EtiologyandMechanismsofInjury

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Traumacanbecausedbymissileornonmissileinjury.Missileinjuryresults frompenetrationoftheskull,meninges,and/orbrainbyanexternalobject, suchasabullet.Gunshotwoundsaremostcommoninadolescentand youngadultmalepatientsbutrelativelyrareinothergroups.

Nonmissileclosedheadinjury(CHI)isamuchmorecommoncauseof neurotraumathanmissileinjury.Fallshavenowsurpassedroadtraffic incidentsastheleadingcauseofTBI.

So-called"groundlevelfalls"(GLFs)areacommonindicationfor neuroimaginginyoungchildrenandolderadults.Insuchcases,braininjury canbesignificant.WithaGLF,asix-foottalladult'sheadimpactstheground

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at20mph.Anticoagulatedolderadultsareespeciallyatrisk forintracranialhemorrhages,evenwithminorheadtrauma.

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Motorvehiclecollisionsoccurringathighspeedexert significantacceleration/decelerationforces,causingthebrain tomovesuddenlywithintheskull.Forcibleimpactionofthe brainagainsttheunyieldingcalvariaandhard,knife-likedura resultsingyralcontusion.Rotationandsuddenchangesin angularmomentummaydeform,stretch,anddamagelong vulnerableaxons,resultinginaxonalinjury.

ClassificationofHeadTrauma

Themostwidelyusedclinicalclassificationofbraintrauma, theGlasgowComaScale(GCS),dependsontheassessmentof threefeatures:besteye,verbal,andmotorresponses.With theuseoftheGCS,TBIcanbedesignatedasamild,moderate, orsevereinjury.

generallyineffectivetechniques(e.g.,skullradiographs)to verysensitivebutexpensivestudies(e.g.,MR).Techniques thatarestillrelativelynewincludeCTandMRperfusion, diffusiontensorimaging(DTI),andfunctionalMRI(fMRI).

SkullRadiography

Fordecades,skullradiography(whethercalled"plainfilm"or, morerecently,"digitalradiography")wastheonlynoninvasive imagingtechniqueavailablefortheassessmentofheadinjury.

Skullradiographyisreasonablyeffectiveinidentifyingcalvarial fractures.Yetskullx-rayscannotdepictthefarmore importantpresenceofextraaxialhemorrhagesand parenchymalinjuries.

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TBIcanalsobedividedchronologicallyandpathoetiologically intoprimaryandsecondaryinjury,thesystemusedinthistext. Primaryinjuriesoccuratthetimeofinitialtrauma.Skull fractures,epi-andsubduralhematomas,contusions,axonal injury,andbrainlacerationsareexamplesofprimaryinjuries.

Secondaryinjuriesoccurlaterandincludecerebraledema, perfusionalterations,brainherniations,andCSFleaks. Althoughvascularinjurycanbeimmediate(bluntimpact)or secondary(vessellacerationfromfractures,occlusion secondarytobrainherniation),forpurposesofdiscussion,itis includedinthechapteronsecondaryinjuries.

CLASSIFICATIONOFHEADTRAUMA

PrimaryEffects

Scalpandskullinjuries

Betweenone-quarterandone-thirdofautopsiedpatientswith fatalbraininjurieshavenoidentifiableskullfracture! Therefore, skullradiographyobtainedsolelyforthepurposeof identifyingthepresenceofaskullfracturehasnoappropriate roleinthecurrentmanagementofthehead-injuredpatient. Withrareexceptions,it'sthebrainthatmatters—notthe skull!

NECT

Becauseofitswideavailabilityandrapiddetectionofacute hemorrhage,CTisnowacceptedastheworldwidescreening toolforimagingacuteheadtrauma.Sinceitsintroduction almost40yearsago,CThasgraduallybutcompletelyreplaced skullradiographsasthe"workhorse"ofbraintraumaimaging. Thereasonsaresimple:CTdepictsbothboneandsofttissue injuries.Itisalsowidelyaccessible,fast,effective,and comparativelyinexpensive.

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• Extraaxialhemorrhage/hematomas

• Parenchymalinjuries

•

• Miscellaneousinjuries

SecondaryEffects

• Cerebraledema

Herniationsyndromes

• Cerebralischemia

BothstandardandmultidetectorrowCT(MDCT)areusedin theinitialimagingofpatientswithtraumaticheadinjury. Identifyingabnormalitiesthatmayrequireurgenttreatment tolimitsecondaryinjuries,suchasbrainswellingand herniationsyndromes,isessential.

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• Vascularinjury(canbeprimaryorsecondary)

•

ImagingAcuteHead Trauma

Imagingisabsolutelycriticaltothediagnosisand managementofthepatientwithacuteTBI.Thegoalof emergentneuroimagingistwofold:(1)identifytreatable injuries,especiallyemergentones,and(2)detectand delineatethepresenceofsecondaryinjuries,suchas herniationsyndromesandvascularinjury.

HowToImage?

Abroadspectrumofimagingmodalitiescanbeusedto evaluatepatientswithTBI.Theserangefromoutdated,

StandardnonenhancedCT(NECT)scans(4or5mmthick) fromjustbelowtheforamenmagnumthroughthevertex shouldbeperformed.Twosetsofimagesshouldbeobtained, oneusingbrainandonewithbonereconstructionalgorithms. Viewingthebrainimageswithawiderwindowwidth(150-200 HU,theso-calledsubduralwindow)shouldbeperformedon PACS(orfilm,ifPACSisnotavailable).Thescoutviewshould alwaysbedisplayedaspartofthestudy(seebelow).

MDCTisnowinwidespreaduse.Coronalandsagittal reformattedimagesusingtheaxialsourcedataareroutinely performedinheadtraumatriageandimprovethedetection rateofacutetraumaticsubduralhematomas.

Three-dimensionalshadedsurfacedisplaysarehelpfulin depictingskullandfacialfractures.IffacialboneCTisalso requested,asingleMDCTacquisitioncanbeobtainedwithout overlappingradiationexposuretotheeyeandlowerhalfof thebrain.

HeadtraumapatientswithacuteintracraniallesionsonCT haveahigherriskforcervicalspinefracturescomparedwith patientswithaCT-negativeheadinjury.Becauseuptoone-

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TraumaOverview

thirdofpatientswithmoderatetosevereheadinjuryas determinedbytheGCShaveconcomitantspineinjury,MDCT ofthecervicalspineisoftenobtainedtogetherwithbrain imaging.Softtissueandbonealgorithmreconstructionswith multiplanarreformattedimagesofthecervicalspineshould beobtained.

RepeatheadCTscansintraumatransfersfromonehospitalto anotherarecommonandaddtobothradiationdose exposureandcost.Inadequatedatatransferfromthe referringhospital—notpoorimagequality—isthemajor reasonforpotentiallypreventablerepeatheadCTscans.

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Asdelayeddevelopmentorenlargementofbothextra-and intracranialhemorrhagesmayoccurwithin24-36hours followingtheinitialtraumaticevent,repeatCTshouldbe obtainedifthereissuddenunexplainedclinicaldeterioration, regardlessofinitialimagingfindings.

CTA

CTangiography(CTA)isoftenobtainedaspartofawholebodytraumaCTprotocol.CraniocervicalCTAshouldalso specificallybeconsidered(1)inthesettingofpenetrating neckinjury,(2)ifafracturedforamentransversariumorfacet subluxationisidentifiedoncervicalspineCT,or(3)ifaskull basefracturetraversesthecarotidcanaloraduralvenous sinus.Arteriallacerationordissection,traumatic pseudoaneurysm,carotid-cavernousfistula,orduralvenous sinusinjuryarenicelydepictedonhigh-resolutionCTA.

Whether—andwhen—toobtainfollow-upimagingintrauma patientsiscontroversial.InalargestudyofchildrenwithGCS scoresof14or15andanormalinitialCTscan,only2%had follow-upCTorMRperformed.Ofthese,only0.05%had abnormalresultsonthefollow-upstudy,andnonerequired surgicalintervention.Thenegativepredictivevaluefor neurosurgicalinterventionforachildwithaninitialGCSof14 or15andnormalCTwas100%.Fromthis,theauthors concludedthatchildrenwithaGCSof14or15andanormal initialheadCTareatverylowriskforsubsequenttraumatic findingsonneuroimagingandextremelylowriskofneeding neurosurgicalintervention.Hospitalizationforneurologic observationofchildrenwithminorheadtraumaafternormal CTscanresultswasdeemedunnecessary.

GLASGOWCOMASCALE

BestEyeResponse(Maximum=4)

1=noeyeopening

MR

AlthoughMRcandetecttraumaticcomplicationswithout radiationandismoresensitiveforabnormalitiessuchas contusionsandaxonalinjuries,thereisgeneralagreement thatNECTistheprocedureofchoiceintheinitialevaluationof braintrauma.LimitationsofMRincludeacquisitiontime, access,patientmonitoringandinstability,motiondegradation ofimages,andcost.

• 2=eyeopeningtopain

• 3=eyesopentoverbalcommand

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Withoneimportantexception—suspectedchildabuse—using MRasaroutinescreeningprocedureinthesettingofacute braintraumaisuncommon.StandardMRtogetherwith susceptibility-weightedimagingandDTIismostusefulinthe subacuteandchronicstagesofTBI.Othermodalitiessuchas fMRIareplayinganincreasinglyimportantroleindetecting subtleabnormalities,especiallyinpatientswithmildcognitive deficitsfollowingminorTBI.

WhoandWhenToImage?

Whotoimageandwhentodoitareparadoxicallybothwell establishedandcontroversial.PatientswithaGCSscore indicatingmoderate(GCS=9-12)orsevere(GCS≤8) neurologicimpairmentareinvariablyimaged.Therealdebate isabouthowbesttomanagepatientswithGCSscoresof1315.

InanattempttoreduceCToverutilizationinemergency departments,severalorganizationshavedevelopedevidencebasedclinicalcriteriathathelpseparate"high-risk"from"lowrisk"patients.(Severalofthesearedelineatedintheboxes below.)Yettheimpactontheemergencydepartment physicianorderingbehaviorhasbeeninconsistent.Inplaces withhighmalpracticerates,manyemergencyphysicians routinelyorderNECTscansoneverypatientwithheadtrauma regardlessofGCSscoreorclinicalfindings.

• 4=eyesopenspontaneously

•

BestVerbalResponse(Maximum=5)

1=none

• 2=incomprehensiblesounds

• 3=inappropriatewords

• 4=confused

•

• 5=oriented

BestMotorResponse(Maximum=6)

1=none

• 2=extensiontopain

• 3=flexiontopain

• 4=withdrawaltopain

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• 5=localizingtopain

•

• 6=obediencetocommands

Sum="ComaScore"andClinicalGrading 13-15=mildbraininjury

• 9-12=moderatebraininjury

•

• ≤8=severebraininjury

AppropriatenessCriteria

Threemajorandwidelyusedappropriatenesscriteriafor imagingacuteheadtraumahavebeenpublished:The AmericanCollegeofRadiology(ACR)Appropriateness Criteria,theNewOrleansCriteria(NOC),andtheCanadian HeadCTRule(CHCR).

ACRCriteria.EmergentNECTinmild/minorCHIwiththe presenceofafocalneurologicdeficitand/orotherriskfactors isdeemed"veryappropriate,"asisimagingalltraumatized childrenunder2yearsofage.Althoughacknowledgingthat NECTinpatientswithmild/minorCHI(GCS≥13)withoutrisk

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(1-1A)AxialNECTscanofaprisonerimagedforhead

showsnogrossabnormality.(CourtesyJ.A.

factorsorfocalneurologicdeficitis"knowntobelowyield," theACRstillratesitas7outof9inappropriateness.

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(1-1B)Scoutviewinthesamecaseshowsaforeignobjectﬅ(a handcuffkey!)intheprisoner'smouth. Hefakedtheinjuryand wasplanningtoescape,buttheradiologistalertedtheguards andthwartedtheplan.(CourtesyJ.A.Junker,MD.)

aswellasinpatientsover65yearsofage,childrenunderthe ageoftwo,anticoagulatedpatients,andpatientswithlossof consciousnessorfocalneurologicdeficit.

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NOCandCHCR.BoththeNOCandCHCRattempttotriage patientswithminimal/mildheadinjuriesinacost-effective manner.AGCSscoreof15(i.e.,normal)withoutanyofthe NOCindicatorsisahighlysensitivenegativepredictorof clinicallyimportantbraininjuryorneedforsurgical intervention.

NEWORLEANSCRITERIAINMINORHEADINJURY

CTindicatedifGCS=15plusanyofthefollowing Headache

• Vomiting

• Patient>60yearsold

• Intoxication(drugs,alcohol)

• Short-termmemorydeficits(anterogradeamnesia)

• Visibletraumaaboveclavicles

• Seizure

Recentstudieshavealsoshownthatcompliancewith establishedimagingguidelinessuchastheCHCRispoor, particularlyinbusyEDsthathandlelargetraumavolumes. Despiteeffortstoeducateurgentcarephysiciansabout limitingpatientexposuretoionizingradiationandusing clinicallybasedriskstratification,nonenhancedheadCTs remainoneofthemostfrequentlyoverutilizedimaging studies.

CTifGCS=13-15andwitnessedLOC,amnesia,or confusion

Highriskforneurosurgicalintervention

GCS<15at2hours

• Suspectedopen/depressedskullfracture

• Clinicalsignsofskullbasefracture

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• AdaptedfromStiellIGetal:ComparisonoftheCanadianCT headruleandtheNewOrleanscriteriainpatientswithminor headinjury.JAMA294(12):1511-1518,2005

AccordingtotheCHCR,patientswithaGCSscoreof13-15and witnessedlossofconsciousness(LOC),amnesia,orconfusion areimaged,alongwiththosedeemed"highrisk"for neurosurgicalinterventionor"mediumrisk"forbraininjury.

Between6-7%ofpatientswithminorheadinjuryhave positivefindingsonheadCTscans.Mostofthesepatientsalso haveheadache,vomiting,drugoralcoholintoxication,seizure, short-termmemorydeficits,orphysicalevidenceoftrauma abovetheclavicles.CTshouldbeusedliberallyinthesecases,

• ≥2vomitingepisodes

• Age≥65years •

MediumriskforbraininjurydetectedbyheadCT

•

Antegradeamnesia≥30minutes

• "Dangerousmechanism"(i.e.,auto-pedestrian, ejectionfromvehicle,etc.)

AdaptedfromStiellIGetal:ComparisonoftheCanadianCT headruleandtheNewOrleanscriteriainpatientswithminor headinjury.JAMA294(12):1511-1518,2005

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trauma

Junker,MD.)

CANADIANHEADCTRULEINMINORHEADINJURY

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(1-2A)Scoutviewina66ywomanwithaCTheadrequestedto evaluategroundlevelfallshowsaposteriorlyangulatedC1odontoidcomplex﬈

TraumaImaging:Keysto Analysis

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(1-2B)TheheadCTinthesamecase(notshown)wasnormal. CervicalspineCTwasthenperformed.Thesagittalimage reformattedfromtheaxialscandatashowsacomminuted, posteriorlyangulateddensfractureﬅ.

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Fourcomponentsareessentialtotheaccurateinterpretation ofCTscansinpatientswithheadinjury:thescoutimageplus brain,bone,andsubduralviewsoftheNECTdataset.Critical informationmaybepresentonjustoneofthesefour components.

SuggestionsonhowtoanalyzeNECTimagesinpatientswith acuteheadinjuryaredelineatedbelow.

ScoutImage

tSAHinmoderatetosevereTBIapproaches100%.tSAHis usuallyfoundinthesulciadjacenttocorticalcontusions,along thesylvianfissures,andaroundtheanteroinferiorfrontaland temporallobes.ThebestplacetolookforsubtletSAHisthe interpeduncularcistern,wherebloodcollectswhenthe patientissupine.

Anyhypodensitywithinanextraaxialcollectionshouldraise suspicionofrapidhemorrhagewithaccumulationof unclottedbloodor(especiallyinalcoholicsorolderpatients) anunderlyingcoagulopathy.Thisisanurgentfindingthat mandatesimmediatenotificationoftheresponsibleclinician. Lookforintracranialair("pneumocephalus").Intracranialairis alwaysabnormalandindicatesthepresenceofafracturethat traverseseithertheparanasalsinusesormastoid.

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BeforeyoulookattheNECTscan,examinethedigitalscout image!Lookforcervicalspineabnormalitiessuchasfractures ordislocations,jawand/orfacialtrauma,andthepresenceof foreignobjects (1-1).Ifthereisasuggestionofcervicalspine fractureormalalignment,MDCTofthecervicalspineshould beperformedbeforethepatientisremovedfromthescanner (1-2).

BrainWindows

Methodicallyandmeticulouslyworkyourwayfromthe outsidein.Firstevaluatethesofttissueimages,beginning withthescalp.Lookforscalpswelling,whichusuallyindicates theimpactpoint.Carefullyexaminetheperiorbitalsoft tissues.

Nextlookforextraaxialblood.Themostcommonextraaxial hemorrhageistraumaticsubarachnoidhemorrhage(tSAH), followedbysub-andepiduralhematomas.Theprevalenceof

Nowmoveontothebrainitself.Carefullyexaminethecortex, especiallythe"high-yield"areasforcorticalcontusions (anteroinferiorfrontalandtemporallobes).Ifthereisascalp hematomaduetoimpact(a"coup"injury),look180°inthe oppositedirectionforaclassic"contre-coup"injury. Hypodenseareasaroundthehyperdensehemorrhagicfoci indicateearlyedemaandseverecontusion.

Moveinwardfromthecortextothesubcorticalwhiteand deepgraymatter.Petechialhemorrhagesoftenaccompany axonalinjury.Ifyouseesubcorticalhemorrhagesontheinitial NECTscan,thisismerelythe"tipoftheiceberg."Thereis usuallyalotmoredamagethanwhatisapparentonthefirst scan.Ageneralrule:thedeeperthelesion,themoresevere theinjury.

Finally,lookinsidetheventriclesforblood-CSFlevelsand hemorrhageduetochoroidplexusshearinginjury.

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Trauma

SubduralWindows

Lookatthesofttissueimagewithbothnarrow("brain")and intermediate("subdural")windows.Smallsubtlesubdural hematomascansometimesbeoverlookedonstandard narrowwindowwidths(75-100HU)yetarereadilyapparent whenwiderwindows(150-200HU)areused.

temporalbonefractures(withorwithoutossicular dislocation),mandibulardislocation("empty"condylarfossa), andcalvarialfractures.Andremember:nondisplacedlinear skullfracturesthatdon'tcrossvascularstructures(suchasa duralvenoussinusormiddlemeningealartery)areinandof themselvesbasicallymeaningless.Thebrainandbloodvessels arewhatmatter!

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BoneCT

BoneCTreferstobonealgorithmreconstructionviewedwith wide(bone)windows.Ifyoucan'tdobonealgorithm reconstructionfromyourdataset,widenthewindowsanduse anedge-enhancementfeaturetosharpentheimage.Threedimensionalshadedsurfacedisplays(3DSSDs)areespecially helpfulindepictingcomplexorsubtlefractures (1-3)

Eventhoughstandardheadscansare4-5mmthick,itisoften possibletodetectfracturesonboneCT.Lookfor basisphenoidfractureswithinvolvementofthecarotidcanal,

Themostdifficultdilemmaisdecidingwhetheranobserved lucencyisafractureoranormalstructure(e.g.,suturelineor vascularchannel).Keepinmind:itisvirtuallyunheardoffora calvarialfracturetooccurintheabsenceofoverlyingsoft tissueinjury.Ifthereisnoscalp"bump,"itisunlikelythatthe lucencyrepresentsanondisplacedlinearfracture.

BoneCTimagesarealsoveryhelpfulindistinguishinglow densityfromairvs.fat.AlthoughmostPACSstationshavea regionofinterest(ROI)functionthatcanmeasure attenuation,fatfadesawayonboneCTimages,andair remainsveryhypodense.

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(1-3A)AxialNECTinan 18ymanwhofelloffhis skateboardshowsasmall rightepiduralhematoma thatalsocontainsairﬆ. (1-3B)Two-millimeter bonealgorithm reconstructioninthesame caseshowsa nondisplacedlinear fractureofthesquamous temporalboneﬅ adjacenttotheepidural bloodandairﬆ.

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(1-3C)Coronal(left)and sagittal(right)boneCTs reconstructedfromthe axialsourcedatashow thetemporalbone fractureﬅiscomminuted andcrossesthemastoid ﬆandmiddleear﬇.(13D)BoneCTwithshaded surfacedisplayinthe samecasenicelyshows thesquamous﬈,mastoid ﬊aspectsofthe nondisplacedbut comminutedfracture.

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TraumaOverview

CTA

CTAisgenerallyindicatedif(1)basilarskullfracturescrossthecarotidcanal oraduralvenoussinus (1-4);(2)ifacervicalspinefracture-dislocationis present,especiallyifthetransverseforaminaareinvolved;or(3)ifthe patienthasstroke-likesymptomsorunexplainedclinicaldeterioration.Both thecervicalandintracranialvasculatureshouldbevisualized.

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Althoughitisimportanttoscrutinizeboththearterialandvenoussidesof thecirculation,aCTAisgenerallysufficient.StandardCTAstypicallyshow boththearteriesandtheduralvenoussinuseswell,whereasaCTvenogram (CTV)oftenmissesthearterialphase.

Examinethesourceimagesaswellasthemultiplanarreconstructionsand maximum-intensityprojection(MIP)reformattedscans.Traumatic dissection,vessellacerations,intimalflaps,pseudoaneurysms,carotidcavernousfistulas,andduralsinusocclusionscangenerallybeidentifiedon CTA.

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ScoutImage

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Evaluatefor

• Cervicalspinefracture-dislocation

○ Jawdislocation,facialfractures

○

○ Foreignobject

BrainWindows

Scalpswelling(impactpoint)

• Extraaxialblood(focalhypodensityinclotsuggestsrapidbleeding)

• Epiduralhematoma

○ Subduralhematoma(SDH)

○ Traumaticsubarachnoidhemorrhage

○ Pneumocephalus

• Corticalcontusion

• Anteroinferiorfrontal,temporallobes

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○ Oppositescalplaceration/skullfracture

○

Hemorrhagicaxonalinjury

• Intraventricularhemorrhage

• SubduralWindows

• BoneCT

150-200HU(forthinSDHsunderskull)

• Anyfracturescrossavascularchannel?

Bonealgorithmreconstruction>bonewindows

•

(1-4B)NECTinthesamecaseshowsdiffusebrain swelling,pneumocephalusﬆ,andtraumatic subarachnoidhemorrhage﬇.

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(1-4C)CTAinthesamecaseshowsthesigmoid sinus﬇isintactbutdisplacedmedially.Note rapidlyenlargingsubgalealhematomaﬅ.

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HEADTRAUMA:CTCHECKLIST

(1-4A)NECTshowspneumocephalusﬆ,baseof skullfracturesﬅadjacenttoair,whichseemsto outlineadisplacedsigmoidsinus﬇.

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Trauma

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SelectedReferences

Introduction

EpidemiologyofHeadTrauma

RoozenbeekBetal:Changingpatternsintheepidemiologyof traumaticbraininjury.NatRevNeurol.9(4):231-6,2013

ImagingAcuteHeadTrauma

HowToImage?

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AmrheinTJetal:Reformattedimagesimprovethedetectionrate ofacutetraumaticsubduralhematomasonbrainCTcompared withaxialimagesalone.EmergRadiol.24(1):39-45,2017

HinzpeterRetal:RepeatedCTscansintraumatransfers:an analysisofindications,radiationdoseexposure,andcosts.EurJ Radiol.88:135-140,2017

RajaASetal:"Choosingwisely"imagingrecommendations:initial implementationinNewEnglandemergencydepartments.WestJ EmergMed.18(3):454-458,2017

ThesleffTetal:Headinjuriesandtheriskofconcurrentcervical spinefractures.ActaNeurochir(Wien).159(5):907-914,2017

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LolliVetal:MDCTimagingoftraumaticbraininjury.BrJRadiol. 20150849,2016

BodanapallyUKetal:Imagingoftraumaticbraininjury.RadiolClin NorthAm.53(4):695-715,viii,2015

WhoandWhenToImage?

GranataRTetal:SafetyofdeferredCTimagingofintoxicated patientspresentingwithpossibletraumaticbraininjury.AmJ EmergMed.35(1):51-54,2017

SharpALetal:Computedtomographyuseforadultswithhead injury:describinglikelyavoidableemergencydepartmentimaging basedontheCanadianCTheadrule.AcadEmergMed.24(1):2230,2017

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AtabakiSMetal:Comparisonofpredictionrulesandclinician suspicionforidentifyingchildrenwithclinicallyimportantbrain injuriesafterbluntheadtrauma.AcadEmergMed.23(5):566-75, 2016

BharadwajSetal:Minorheadinjury:limitingpatientexposureto ionizingradiation,riskstratification,andconcussionmanagement. CurrOpinPediatr.28(1):121-31,2016

LolliVetal:MDCTimagingoftraumaticbraininjury.BrJRadiol. 20150849,2016

SadeghRetal:HeadCTscaninIranianminorheadinjurypatients: evaluatingcurrentdecisionrules.EmergRadiol.23(1):9-16,2016

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ArabAFetal:AccuracyofCanadianCTheadruleinpredicting positivefindingsonCToftheheadofpatientsaftermildhead injuryinalargetraumacentreinSaudiArabia.NeuroradiolJ. 28(6):591-7,2015

BodanapallyUKetal:Imagingoftraumaticbraininjury.RadiolClin NorthAm.53(4):695-715,viii,2015

GunesTatarIetal:AppropriatenessofselectioncriteriaforCT examinationsperformedatanemergencydepartment.Emerg Radiol.21(6):583-8,2014

RyanMEetal:ACRappropriatenesscriteriaheadtrauma--child.J AmCollRadiol.11(10):939-47,2014

StiellIGetal:ComparisonoftheCanadianCTHeadRuleandthe NewOrleansCriteriainpatientswithminorheadinjury.JAMA. 294(12):1511-8,2005

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PrimaryEffectsofCNSTrauma

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Primary head injuries are defined as those that occur at the time of initial trauma even though they may not be immediately apparent on initial evaluation.

Headinjurycanbecausedbydirectorindirecttrauma.Directtrauma involvesablowtotheheadandisusuallycausedbyautomobilecollisions, falls,orinjuryinflictedbyanobjectsuchasahammerorbaseballbat.Scalp lacerations,hematomas,andskullfracturesarecommon.Associated intracranialdamagerangesfromnonetosevere.

Significantforcesofacceleration/deceleration,lineartranslation,and rotationalloadingcanbeappliedtothebrainwithoutdirectheadblows. Suchindirecttraumaiscausedbyangularkinematicsandtypicallyoccursin high-speedmotorvehiclecollisions(MVCs).Herethebrainundergoesrapid deformationanddistortion.Dependingonthesiteanddirectionoftheforce applied,significantinjurytothecortex,axons,penetratingbloodvessels,and deepgraynucleimayoccur.Severebraininjurycanoccurintheabsenceof skullfracturesorvisiblescalplesions.

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Webeginourdiscussionwithaconsiderationofscalpandskulllesionsaswe workourwayfromtheoutsidetotheinsideoftheskull.Wethendelineate thespectrumofintracranialtrauma,startingwithextraaxialhemorrhages. Weconcludethischapterwithadetaileddiscussionofinjuriestothebrain parenchyma(e.g.,corticalcontusion,diffuseaxonalinjury,andtheserious deepsubcorticalinjuries).

ScalpandSkullInjuries

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Scalpandskullinjuriesarecommonmanifestationsofcranialtrauma. Althoughbraininjuryisusuallythemostimmediateconcerninmanaging traumatizedpatients,superficiallesionssuchasscalpswellingandfocal hematomacanbehelpfulinidentifyingthelocationofdirectheadtrauma. Onoccasion,theseinitiallyinnocent-appearing"lumpsandbumps"can becomelife-threatening.Beforeturningourattentiontointracranial traumaticlesions,wethereforebrieflyreviewscalpandskullinjuries, delineatingtheirtypicalimagingfindingsandclinicalsignificance.

ScalpInjuries

Scalpinjuriesincludelacerationsandhematomas.Scalplacerationscan occurinbothpenetratingandclosedheadinjuries.Lacerationsmayextend partiallyorentirelythroughallfivelayersofthescalp(skin,subcutaneous fibrofattytissue,galeaaponeurotica,looseareolarconnectivetissue,and periosteum)totheskull (2-1)

Focaldiscontinuity,softtissueswelling,andsubcutaneousairarecommonly identifiedinscalplacerations.Scalplacerations

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(2-1)Coronalgraphic depictsnormallayersof thescalp.Skin, subcutaneousfibrofatty tissueoverliethegalea aponeurotica﬊,loose areolarconnectivetissue. Thepericranium﬉isthe periosteumoftheskull andcontinuesintoand throughsuturestomerge withtheperiosteallayer ofthedura﬇.(2-2)NECT showsscalplacerationﬆ, hyperdenseforeignbodies ﬅ,andsubgalealair﬇.

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(2-3)Graphicshowsthe skullofanewborn, includingtheanterior fontanelle,coronal, metopic,sagittalsutures. Cephalohematoma﬈is subperiosteal,limitedby sutures.Subgaleal hematoma﬇isunderthe scalpaponeurosis,not boundedbysutures.(24A)NECTscanina newbornshowsasmall rightﬅandalargeleft ﬆparietal cephalohematoma. Neithercrossesthe sagittalsuture﬇.

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(2-4B)Coronalscaninthe samecaseshowsthe smallrightﬅ,largeleftsidedcephalohematomas ﬆ.Theelevated periosteum﬇clearly separatesthetwoblood collections.(2-4C)Sagittal scanreformattedfromthe axialdatashowsthatthe leftparietal cephalohematomaﬆ doesnotcrossthecoronal suture﬇.

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PrimaryEffectsofCNSTrauma

forthepresenceofanyforeignbodies.Ifnotremovedduring wounddebridement,foreignbodiescanbeapotentialsource ofsubstantialmorbidityandareveryimportanttoidentifyon initialimagingstudies.Woodfragmentsareoftenhypodense, whereasleadedglass,gravel,andmetallicshardsarevariably hyperdense (2-2).

Cephalohematomasaretheextracranialequivalentofan intracranialepiduralhematoma.Cephalohematomasdonot crosssuturelinesandaretypicallyunilateral.Becausetheyare anatomicallyconstrainedbythetoughfibrousperiosteumand itsinsertions,cephalohematomasrarelyattainlargesize.

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Scalplacerationsmayormaynotbeassociatedwithscalp hematomas.Therearetwodistinctlydifferenttypesofscalp hematomas:cephalohematomasandsubgalealhematomas. Theformerareusuallyofnoclinicalsignificance,whereasthe lattercancausehypovolemiaandhypotension.

Cephalohematomasaresubperiostealbloodcollectionsthat lieinthepotentialspacebetweentheoutersurfaceofthe calvariumandthepericranium,whichservesasthe periosteumoftheskull (2-3).Thepericraniumcontinues mediallyintocranialsuturesandisanatomicallycontiguous withtheouter(periosteal)layerofthedura.

Cephalohematomasoccurin1%ofnewbornsandaremore commonfollowinginstrumenteddelivery.Theyareoften diagnosedclinicallybutimagedonlyiftheyareunusually prominentorifintracranialinjuriesaresuspected.NECTscans showasomewhatlens-shapedsofttissuemassthatoverliesa singlebone(usuallytheparietaloroccipitalbone) (2-4).If morethanoneboneisaffected,thetwocollectionsare separatedbytheinterveningsuturelines.

Complicationsfromcephalohematomaarerare,andmost resolvespontaneouslyoverafewdaysorweeks.Occasionally theelevatedperiosteumattheperipheryofachronic cephalohematomaundergoesdystrophiccalcification, creatingafirmpalpablemass.

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(2-5)Autopsyfroma traumatizedinfantshows amassivebiparietal subgalealhematomaﬅ. Thegaleaaponeurotica hasbeenpartiallyopened ﬊toshowlarge biparietalhematomathat crossesthesagittalsuture ﬉.(2-6)AxialCECTin3y childshowsmassive subgalealhematomaﬅ surroundingentire calvarium.Subgaleal hematomascrosssutures, canbecomelifethreatening,while cephalohematomasare anatomicallylimited.

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(2-7)Autopsiedskull showsfataltraumawith exo-(L)andendocranial views(R).Alinear fracture﬈extendsinto thesuperiorsagittal suture﬊,causing diastasisandasubgaleal hematomaﬆ.(2-8)Bone CTthroughthetopofthe calvariumshowslinear skullfracturesﬅ extendingintoand wideningthesagittal suture,causingadiastatic fracture﬇.

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Trauma

Subgalealhematomasaresubaponeuroticcollectionsandare commonfindingsintraumatizedpatientsofallages.Here bloodcollectsundertheaponeurosis(the"galea")ofthe occipitofrontalismuscle (2-5).Becauseasubgalealhematoma liesdeeptothescalpmusclesandgaleaaponeuroticabut externaltotheperiosteum,itisnotanatomicallylimitedby suturelines.

Bleedingintothesubgalealspacecanbeveryextensive. Subgalealhematomasareusuallybilaterallesionsthatoften spreaddiffuselyaroundtheentirecalvaria.NECTscansshowa heterogeneouslyhyperdensecrescenticscalpmassthat crossesoneormoresuturelines (2-6).

FacialInjuries

Facialfracturesarecommonlyoverlookedoninitialimaging (typicallyheadCTscans).Importantsofttissuemarkerscanbe identifiedthatcorrelatewithfacialfracturesandmaymerita dedicatedCTevaluationofthefacialbones.Theseinclude periorbitalcontusionsandsubconjunctivalhemorrhageaswell aslacerationsofthelips,mouth,andnose.

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Mostsubgalealhematomasresolvewithouttreatment.In contrasttobenignself-limitedcephalohematomas,however, expandingsubgalealhematomasininfantsandsmallchildren cancausesignificantbloodloss.

Holmgrenetal.(2005)haveproposedthemnemonicLIPS-N (liplaceration,intraorallaceration,periorbitalcontusion, subconjunctivalhemorrhage,andnasallaceration)beusedin conjunctionwithphysicalexamination.Ifanyoftheseis present,atraumatizedpatientshouldhaveadedicatedfacial CTinadditiontothestandardheadCT.

SkullFractures

Noticingascalp"bump"orhematomaoninitialimagingin headtraumaisimportant,ascalvarialfracturesrarely—if

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(2-9)3Dshadedsurface display(SSD)inapatient withmultiplelinear﬈ anddiastatic﬉skull fracturesshowsutilityof SSDsindepictingcomplex fractureanatomy.Note slightdepression﬇of thefracturedparietooccipitalcalvarium.(210A)AxialboneCTina patientwhowashitinthe headwithafallingladder showsanextensively comminuted,depressed skullfracture﬇.

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(2-10B)CoronalboneCT reformattedfromthe axialsourcedatainthe samecaseshowsthatthe depressedskullfracture ﬇isnearthemidline, raisingconcernfor superiorsagittalsinus injury.(2-10C)Sagittal boneCTinthesamecase showsthedepressedskull fracture﬇,associated withafocalscalp hematomaﬆ.CTV(not shown)demonstratedSSS narrowingwithout occlusionorvenousEDH.

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PrimaryEffectsofCNSTrauma

ever—occurintheabsenceofoverlyingsofttissueswellingor scalplaceration.SkullfracturesarepresentoninitialCTscans inabouttwo-thirdsofpatientswithmoderateheadinjury, although25-35%ofseverelyinjuredpatientshaveno identifiablefractureevenwiththin-sectionbone reconstructions.

LinearSkullFractures

Alinearskullfractureisasharplymarginatedlineardefect thattypicallyinvolvesboththeinnerandoutertablesofthe calvaria (2-8).

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Skullfracturescanbesimpleorcomminuted,closedoropen. Inopenfractures,skinlacerationresultsincommunication betweentheexternalenvironmentandintracranialcavity. Infectionriskishighinthistypeoffracture,asitiswith fracturesthatcrossthemastoidsandparanasalsinuses.

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Mostlinearskullfracturesarecausedbyrelativelylow-energy blunttraumathatisdeliveredoverarelativelywidesurface area.Linearskullfracturesthatextendintoandwidenasuture becomediastaticfractures(seebelow).Whenmultiple complexfracturesarepresent,3Dshadedsurfacedisplay (SSD)canbeveryhelpfulindepictingtheiranatomyand relationshipstocranialsutures.

Severaltypesofacuteskullfracturecanbeidentifiedon imagingstudies:linear,depressed,elevated,anddiastatic fractures (2-7).Fracturescaninvolvethecalvaria,skullbase, orboth.Anothertypeofskullfracture,a"growing"skull fracture,isararebutimportantcomplicationofskulltrauma.

Patientswithanisolatedlinearnondisplacedskullfracture (NDSF),nointracranialhemorrhageorpneumocephalus, normalneurologicexamination,andabsenceofotherinjuries areatverylowriskfordelayedhemorrhageorotherlifethreateningcomplication.Hospitalizationisnotnecessaryfor manychildrenwithNDSFs.

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(2-11A)AxialNECTscan showsseverescalp laceration﬇witha combinationofelevated ﬆ,depressed﬉skull fractures.(2-11B)BoneCT inthesamecaseshows thattheelevatedfracture isliterally"hinged"away fromthecalvaria.

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(2-12A)AxialNECTscan ina20ymanwhohada treefallonhishead showsamassive subgalealhematoma﬇ crossingtheanterior aspectofthesagittal sutureﬅ.Asmall extraaxialhematomaﬆ, mostlikelyavenous epiduralhematoma,is present.(2-12B)BoneCT inthesamecaseshowsa diastaticfractureofthe sagittalsutureﬅ. Nondisplacedlinear fractures﬊arealso present.

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Trauma

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DepressedSkullFractures

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Adepressedskullfractureisafractureinwhichthe fragmentsaredisplacedinward (2-9).Comminutionofthe fracturefragmentsstartsatthepointofmaximumimpactand spreadscentrifugally.Depressedfracturesaremostoften causedbyhigh-energydirectblowstoasmallsurfacewitha bluntobject(e.g.,hammer,baseballbat,ormetalpipe) (2-10)

Depressedskullfracturestypicallyteartheunderlyingdura andarachnoidandareassociatedwithcorticalcontusionsand potentialleakageofCSFintothesubduralspace.Fractures extendingtoaduralsinusorthejugularbulbareassociated withvenoussinusthrombosisin40%ofcases.

ElevatedSkullFractures

Anelevatedskullfracture—oftencombinedwithdepressed fragments—isuncommon.Elevatedfracturesareusually causedbyalong,sharpobject(suchasamacheteorpropeller)

thatfracturesthecalvaria,simultaneouslyliftingandrotating thefracturefragment (2-11)

DiastaticSkullFractures

Adiastaticskullfractureisafracturethatwidens("diastases" or"splitsopen")asutureorsynchondrosis.Diastaticskull fracturesusuallyoccurinassociationwithalinearskull fracturethatextendsintoanadjacentsuture (2-12)

Traumaticdiastasisofthesphenooccipital,petrooccipital, and/oroccipitomastoidsynchondrosesiscommoninchildren withseverelycomminutedcentralskullbasefractures.Asit typicallydoesnotossifycompletelyuntilthemidteens,the sphenooccipitalsynchondrosisisthemostcommonsite.

"Growing"SkullFractures

A"growing"skullfracture(GSF),alsoknownas "posttraumaticleptomeningealcyst"or"craniocerebral

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(2-13A)AxialNECTscan inapatientwith progressiveright hemiparesisfollowing priorheadtraumashows leftparietal encephalomalaciaﬅ.The overlyingskullappears focallydeformedand thinned﬈.(2-13B)Bone CTinthesamepatient showsawidelucentskull lesionwithrounded, scallopedmargins﬈.

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(2-13C)AxialT2WIinthe samepatientshowsa lobulatedCSFcollection ﬅthatextendsintoand almostcompletely throughthecalvarial vault.(2-13D)Coronal T2WIshowsthe intradiploicCSFcollection ﬅwithencephalomalacic brainstretchedand tetheredintothelesion ﬊.Thisisclassic "growing"skullfracture (leptomeningealcyst).

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PrimaryEffectsofCNSTrauma

erosion,"isararelesionthatoccursinjust0.3-0.5%ofallskullfractures (213).MostpatientswithGSFareunder3yearsofage.

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GSFsdevelopinstagesandslowlywidenovertime.Inthefirst"prephase,"a skullfracture(typicallyalinearorcomminutedfracture)laceratesthedura, andbraintissueorarachnoidmembraneherniatesthroughthetorndura. StageIextendsfromthetimeofinitialinjurytojustbeforethefracture enlarges.EarlyrecognitionandduralrepairofstageIGSFsproducethebest results.

StageIIistheearlyphaseofGSF.StageIIlastsforapproximately2months followinginitialfractureenlargement.Atthisstage,thebonedefectissmall, theskulldeformityisrelativelylimited,andneurologicdeficitsaremild. Nevertheless,theentrappedtissuepreventsnormalfracturehealing.

StageIIIrepresentslate-stageGSFandbegins2monthsaftertheinitial enlargementbegins.Duringthisstage,thebonedefectbecomes significantlylarger.BraintissueandCSFextendbetweenthebonyedgesof thefracturethroughtornduraandarachnoid.

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Patientswithlate-stageGSFsoftenpresentmonthsorevenyearsafterhead trauma.StageIIIGSFscancausepronouncedskulldeformitiesand progressiveneurologicdeficitsifleftuntreated.

Imaging

GeneralFeatures.Plainskullradiographshavenoroleinthemodern evaluationoftraumaticheadinjury.One-quarterofpatientswithfatalbrain injurieshavenoskullfractureatautopsy.CTisfast,widelyavailable,sensitive forbothboneandbraininjury,andtheworldwidediagnosticstandardof careforpatientswithheadinjuries.NewgenerationsofmultisliceCT scannersofferveryshortacquisitiontimeswithexcellentspatialresolution.

Bothboneandsofttissuereconstructionalgorithmsshouldbeusedwhen evaluatingpatientswithheadinjuries.Softtissuereconstructionsshouldbe viewedwithbothnarrow("brain")andintermediate("subdural")windows. Coronalandsagittalreformattedimagesobtainedusingtheaxialsource dataarehelpfuladditions.

Three-dimensionalreconstructionandcurvedMIPsoftheskullhavebeen showntoimprovefracturedetectionovertheuseofaxialsectionsalone.

CTFindings.Whilefracturescaninvolveanypartofthecalvariaorskullbase, themiddlecranialfossaismostsusceptiblebecauseofitsthin"squamous" bonesandmultipleforaminaandfissures.

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﬇fracturesofthe skullbasearepresentcrossingthejugular foramenﬆ,bothcarotidcanals﬈.

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NECTscansdemonstratelinearskullfracturesassharplymarginatedlucent lines.Depressedfracturesaretypicallycomminutedandshowinward implosionoffracturefragments (2-10) Elevatedfracturesshowanelevated, rotatedskullsegment (2-11).Diastaticfracturesappearaswidenedsutures orsynchondroses (2-14) (2-15)andareusuallyassociatedwithlinearskull fractures.

StageI"growing"fracturesaredifficulttodetectoninitialNECTscans,as scalpandcontusedbrainaresimilarindensity.Identifyingtorndurawith herniatedbraintissueissimilarlydifficultalthoughcranialultrasoundcanbe morehelpful.

Later-stageGSFsdemonstrateaprogressivelywideningandunhealing fracture.Alucentskulllesionwithrounded,scallopedmarginsandbeveled edgesistypical (2-13).CSFandsofttissueareentrappedwithinthe expandingfracture.MostGSFsaredirectlyadjacenttoposttraumatic encephalomalacia,sotheunderlyingbrainoftenappearshypodense.

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(2-15B)CTinthesamecaseshowscarotid arteriesﬅ,sigmoidsinuses﬊arepatent.A smallrightvenousEDHﬆispresent.

(2-15A)Linearﬅ,diastatic

(2-14)Autopsyshowsmultipleskullbase fracturesinvolvingclivusﬅ,carotidcanals﬇, jugularforaminaﬆ.(E.T.Hedley-White,MD.)

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MRFindings.MRisrarelyusedinthesettingofacuteheadtraumabecause ofhighcost,limitedavailability,andlengthytimerequired.Comparedwith CT,bonedetailispooralthoughparenchymalinjuriesarebetterseen. AddingT2*sequences,particularlySWI,isespeciallyhelpfulinidentifying hemorrhagiclesions.

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Insomecases,MRmaybeindicatedforearlydetectionofpotentially treatablecomplications.Ayoungchildwithneurologicdeficitsorseizures,a fracturelargerthan4millimeters,orasofttissuemassextendingthrough thefractureintothesubgalealspaceisatriskfordevelopingaGSF.MRcan demonstratetheduraltearanddifferentiateherniatedbrainfromcontused, edematousscalp.

Angiography.Ifafracturecrossesthesiteofamajorvascularstructuresuch asthecarotidcanaloraduralvenoussinus (2-14),CTangiographyis recommended.Sagittal,coronal,andMIPreconstructionshelpdelineatethe siteandextentofvascularinjuries.

(2-16)GraphicshowsEDH﬈,depressedskull fracture﬇laceratingmiddlemeningealartery ﬆ.Insetshowsrapidbleeding,"swirl"signﬅ.

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Clivalandskullbasefracturesarestronglyassociatedwithneurovascular trauma,andCTAshouldalwaysbeobtainedinthesecases (2-15).Cervical fracturedislocations,distractioninjuries,andpenetratingnecktraumaalso meritfurtherinvestigation.Uncomplicatedasymptomaticsofttissueinjuries oftheneckrarelyresultinsignificantvascularinjury.

SCALPANDSKULLINJURIES

ScalpInjuries

Lacerations

• ±Foreignbodies

○ Cephalohematoma

• Usuallyinfants ○ Subperiosteal

○ Small,unilateral(limitedbysutures)

○ Subgalealhematoma

• Betweengalea,periosteumofskull

○ Circumferential,notlimitedbysutures

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(2-17A)Endocranialviewshowstemporalbone fracture﬇crossingthemiddlemeningealartery grooveﬆ.NotebiconvexmarginsofEDH﬈.

○

○ Canbeverylarge,life-threatening

SkullFractures

Linear

• Sharplucentline

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○ Depressed

Canbeextensiveandwidespread

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view

(CourtesyE.T.Hedley-Whyte,MD.)

• Focal

○ Inwardlydisplacedfragments

○

○ Oftenlaceratesdura-arachnoid

• Rare

Elevated

○

Fragmentedrotatedoutward ○ Diastatic

• Typicallyassociatedwithseveretrauma ○ Usuallycausedbylinearfracturethatextendsintosuture

•

○ Widens,spreadsapartsutureorsynchondrosis

○ "Growing"

○

Rare

Usuallyinyoungchildren

Fracturelaceratesdura-arachnoid ○

○

Brain/arachnoidherniatesthroughtorndura

Trappedtissuepreventsbonehealing

CT:Roundededges,scallopedmarginsofskull

MR:CSF±brain

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(2-17B)Dorsal

ofthedura-coveredbrain showsthebiconvexEDHﬅontopofthedura.

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PrimaryEffectsofCNSTrauma

ExtraaxialHemorrhages

Extraaxialhemorrhagesandhematomasarecommonmanifestationsof headtrauma.Theycanoccurinanyintracranialcompartment,withinany space(potentialoractual),andbetweenanylayersofthecranialmeninges. Onlythesubarachnoidspacesexistnormally;alltheotherspacesare potentialspacesandoccuronlyunderpathologicconditions.

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Epiduralhematomasarisebetweentheinnertableoftheskullandouter (periosteal)layerofthedura.Subduralhematomasarelocatedbetweenthe inner(meningeal)layeroftheduraandthearachnoid.Traumatic subarachnoidhemorrhageisfoundwithinthesulciandsubarachnoid cisterns,betweenthearachnoidandthepia.

Todiscussextraaxialhemorrhages,weworkourwayfromtheoutsideto inside.Wethereforebeginthissectionwithadiscussionofepidural hematomas(bothclassicandvariant),thenmovedeeperinsidethecranium tothemorecommonsubduralhematomas.Weconcludewitha considerationoftraumaticsubarachnoidhemorrhage.

(2-18A)BiconvexaEDHﬅisshownwithathin subduralbloodcollectionalongthetentorium, falx﬇,andlefthemisphereﬆ.

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ArterialEpiduralHematoma

Epiduralhematomas(EDHs)areuncommonbutpotentiallylethal complicationsofheadtrauma.IfanEDHispromptlyrecognizedand appropriatelytreated,mortalityandmorbiditycanbeminimized.

Terminology

AnEDHisacollectionofbloodbetweenthecalvariaandouter(periosteal) layerofthedura.

Etiology

MostEDHsarisefromdirecttraumatotheskullthatlaceratesanadjacent bloodvessel (2-16).Thevastmajority(90%)arecausedbyarterialinjury, mostcommonlytothemiddlemeningealartery.Approximately10%of EDHsarevenous,usuallysecondarytoafracturethatcrossesaduralvenous sinus(seebelow).

Pathology

Location.Over90%ofEDHsareunilateralandsupratentorial.Between9095%arefounddirectlyadjacenttoaskullfracture.Thesquamousportionof thetemporalboneisthemostcommonsite.

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(2-18B)(L)BoneCTshowssubgalealhematoma ﬇,EDHﬅ.(R)CoronalboneCTdemonstratesa subtlecomminutedfractureﬆ.

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GrossPathology.EDHsarebiconvexinshape (2-17A).Adherenceofthe periostealduratotheinnercalvariaexplainsthistypicalconfiguration.As EDHsexpand,theystriptheduraawayfromtheinnertableoftheskull, formingtheclassiclens-shapedhematoma (2-17B).Becausethedurais especiallytightlyattachedtosutures,EDHsinadultsrarelycrosssuturelines (10%ofEDHsinchildrendocrosssutures,especiallyifafracturetraverses thesutureorsuturaldiastasisispresent).

ThetypicalgrossorintraoperativeappearanceofanacuteEDHisadark purple("currantjelly")lentiformclot.

ClinicalIssues

Epidemiology.EDHsaremuchlesscommonthaneithertraumatic subarachnoidhemorrhage(tSAH)orsubduralhematoma.AlthoughEDHs representupto10%offatalinjuriesinautopsyseries,theyarefoundinonly 1-4%ofpatientsimagedforcraniocerebraltrauma.

AxialNECTshowsanactivelybleedingEDH with"swirl"sign﬊,displacedcortex﬈.Afocal cephalohematomaﬅispresent.

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(2-19)

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Trauma

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Demographics.EDHsareuncommonininfantsandtheelderly.Mostare foundinolderchildrenandyoungadults.TheM:Fratiois4:1.

Presentation.Theprototypical"lucidinterval,"duringwhichatraumatized patienthasaninitialbrieflossofconsciousnessfollowedbyan asymptomaticperiodofvariouslengthpriortoonsetofcomaand/or neurologicdeficit,occursinonly50%ofEDHcases.Headache,nausea, vomiting,symptomsofintracranialmasseffect(e.g.,pupil-involvingthird cranialnervepalsy)followedbysomnolenceandcomaarecommon.

NaturalHistory.Outcomedependsonsizeandlocationofthehematoma, whethertheEDHisarterialorvenous,andwhetherthereisactivebleeding (seebelow).Intheabsenceofotherassociatedtraumaticbraininjuries, overallmortalityratewithpromptrecognitionandappropriatetreatmentis under5%.

(2-20A)Serialimagingdemonstratestemporal evolutionofasmallnonoperatedEDH.Initial NECTscanshowsahyperdensebiconvexEDH﬇.

DelayeddevelopmentorenlargementofanEDHoccursin10-15%ofcases, usuallywithin24-36hoursfollowingtrauma.

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TreatmentOptions.ManyEDHsarenowtreatedconservatively.Most traumaticEDHsarenotsurgicallesionsatinitialpresentation,andtherateof conversiontosurgeryislow.MostvenousandsmallclassichyperdenseEDHs thatdonotexhibita"swirl"signandhaveminimalornomasseffectare managedconservativelywithcloseclinicalobservationandfollow-up imaging (2-20).SignificantclinicalpredictorsofEDHprogressionrequiring conversiontosurgicaltherapyarecoagulopathyandyoungerage.

Imaging

GeneralFeatures.EDHs,especiallyinadults,typicallydonotcrosssutures unlessafracturewithsuturaldiastasisispresent.Inchildren,10%ofEDHs crosssuturelines,usuallythecoronalorsphenosquamoussuture.

Lookforothercomorbidlesionssuchas"contre-coup"injuries,tSAH,and secondarybrainherniations,allofwhicharecommonfindingsinpatients withEDHs.

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(2-20B)Repeatscan10dayslaterrevealsthat densityoftheEDH﬇hasdecreased significantly.

CTFindings.NECTscanistheprocedureofchoiceforinitialimagingin patientswithheadinjury.Bothsofttissueandbonereconstruction algorithmsshouldbeobtained.Multiplanarreconstructionsareespecially usefulinidentifyingvertexEDHs,whichmaybedifficulttodetectifonlyaxial imagesareobtained.

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(2-20C)Repeatstudy6weeksaftertrauma revealsthattheEDHhasresolvedcompletely.

Theclassicimagingappearanceofclassic(arterial)EDHsisahyperdense (60-90HU)biconvexextraaxialcollection (2-18).Presenceofahypodense component("swirl"sign)isseeninaboutone-thirdofcasesandindicates active,rapidbleedingwithunretractedclot (2-16) (2-19).

EDHscompresstheunderlyingsubarachnoidspaceanddisplacethecortex medially,"buckling"thegray-whitematterinterfaceinward.

AirinanEDHoccursinapproximately20%ofcasesandisusually—butnot invariably—associatedwithasinusormastoidfracture.

Patientswithmixed-densityEDHstendtopresentearlierthanpatientswith hyperdensehematomasandhavelowerGlasgowComaScores(GCSs),larger hematomavolumes,andpoorerprognosis.

Imagingfindingsassociatedwithadverseclinicaloutcomearethickness>1.5 cm,volume>30mL,pterional(lateralaspectofthemiddlecranialfossa) location,midlineshift>5mm,andpresenceofa"swirlsign"withinthe hematomaonimaging.

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PrimaryEffectsofCNSTrauma

MRFindings.AcuteEDHsaretypicallyisointensewithunderlyingbrain, especiallyonT1WI.Thedisplacedduracanbeidentifiedasadisplaced"black line"betweenthehematomaandthebrain.

Angiography.DSAmayshowalaceratedmiddlemeningealarterywith "tram-track"fistulizationofcontrastfromthemiddlemeningealarteryinto thepairedmiddlemeningealveins.Masseffectwithdisplacedcortical arteriesandveinsisseen.

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CLASSICACUTEEPIDURALHEMATOMA

Terminology

• Etiology

EDH=bloodbetweenskull,dura

• Arterial90%

Associatedskullfracturein90-95%

• Mostoftenmiddlemeningealartery

○ Venous10%

• Pathology

Unilateral,supratentorial(>90%)

Graphic

basilarskullfracture﬈ withtransversesinusocclusion﬊andposterior fossavenousEDHﬆ.

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• Durastrippedawayfromskull→biconvexhematoma

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• Usuallydoesnotcrosssutures(exception=children,10%)

• Doescrosssitesofduralattachment

• Clinical

Rare(1-4%ofheadtrauma)

• Olderchildren,youngadultsmostcommon

• M:F=4:1

• Classic"lucidinterval"inonly50%

• Delayeddeteriorationcommon

• Lowmortalityifrecognized,treated

• SmallEDHs

• Ifminimalmass,no"swirlsign"oftenmanagedconservatively

○

Imaging

Hyperdenselens-shaped

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•

• "Swirlsign"(hypodensity)=rapidbleeding

VenousEpiduralHematoma

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NotallEDHsarethesame!!VenousEDHsareoftensmaller,areunderlower pressure,anddevelopmoreslowlythantheirarterialcounterparts.Most venousEDHsarecausedbyaskullfracturethatcrossesaduralvenoussinus andthereforeoccurintheposteriorfossaneartheskullbase (transverse/sigmoidsinus) (2-21)orthevertexofthebrain(superiorsagittal sinus).Incontrasttotheirarterialcounterparts,venousEDHscan"straddle" intracranialcompartments,crossingbothsuturesandlinesofdural attachment (2-22)andcompressingoroccludingtheadjacentvenous sinuses.

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VenousEDHscanbesubtleandeasilyoverlooked.Coronalandsagittal reformattedimagesarekeytothediagnosisanddelineationofthesevariant EDHs (2-23).SeveralanatomicsubtypesofvenousEDHs,eachwithdifferent treatmentimplicationsandprognosis,arerecognized.

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VertexEDH

"Vertex"EDHsarerare.Usuallycausedbyalinearordiastaticfracturethat crossesthesuperiorsagittalsinus,theyoftenaccumulateoverhoursoreven dayswithslow,subtleonsetofsymptoms (2-24)."Vertex"hematomascan besubtleandareeasilyoverlookedunlesscoronalandsagittalreformatted imagesareobtained.

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(2-23)(L)Coronal,(R)sagittalCTVshowsvenous EDH﬇straddlingthetentoriumﬅ,elevating thelefttransversesinusﬆ.

(2-22)AutopsyshowsthatvenousEDH﬊caused bytransversesinusinjury"straddles"the tentoriumﬅ.(CourtesyR.Hewlett,MD.)

(2-21)

shows

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Trauma

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AnteriorTemporalEDH

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AnteriortemporalEDHsareauniquesubgroupofhematomasthatoccurin theanteriortipofthemiddlecranialfossa.AnteriortemporalEDHsare causedeitherbyanisolatedfractureoftheadjacentgreatersphenoidwing orbyanisolatedzygomaticomaxillarycomplex("tripod")facialfracture.The sphenoparietalduralvenoussinusisinjuredasitcurvesmediallyalongthe undersurfaceofthelessersphenoidwing,extravasatingbloodintothe epiduralspace.Limitedanatomicallybythesphenotemporalsuturelaterally andtheorbitalfissuremedially,anteriortemporalEDHsremainstableinsize anddonotrequiresurgicalevacuation (2-25) (2-26)

ClivalEDH

(2-24A)BoneCTina57ymanshowsalinearskull fractureﬅthatcrossesthemidline.Noother abnormalitieswerepresent.

ClivalEDHsusuallydevelopafterahyperflexionorhyperextensioninjuryto theneckandarepossiblycausedbystrippingofthetectorialmembrane fromattachmentstotheclivus.Lesscommonly,theyhavebeenassociated withbasilarskullfracturesthatlaceratetheclivalduralvenousplexus.

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ClivalEDHsmostoftenoccurinchildrenandpresentwithmultiplecranial neuropathies.Theabducensnerveisthemostcommonlyaffected,followed bytheglossopharyngealandhypoglossalnerves.Theyaretypicallylimitedin sizebythetightattachmentoftheduratothebasisphenoidandtectorial membrane (2-27)

VENOUSEPIDURALHEMATOMA

NotallEDHsarethesame!

• Prognosis,treatmentvary

Differentetiologiesindifferentanatomiclocations

• VenousEDHs=10%ofallEDHs

• Cancrosssutures,duralattachments

Skullfracturecrossesduralvenoussinus

○ Oftensubtle,easilyoverlooked

• Coronal,sagittalreformattedimageskeytodiagnosis

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○ Usuallyaccumulateslowly

• Canbelimitedinsize;oftentreatedconservatively

• Subtypes

(2-24B)CTvenogramafterthepatient deterioratedshowsalargevenousEDH﬊.The middleSSSiscompressedandthrombosedﬆ.

•

VertexEDH

○ SSScanbelacerated,compressed,thrombosed

Skullfracturecrossessuperiorsagittalsinus(SSS)

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○ Hematomaunderlowpressure,developsgradually

○ Slowonsetofsymptoms

(2-24C)CoronalscanshowsavertexvenousEDH crossingthemidline﬊.ThethrombosedSSSﬆ, corticalveinsaredisplacedinferiorlyﬅ.

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○

○ Maybecomelarge,causesignificantmasseffect

AnteriortemporalEDH

• Sphenoidwingorzygomaticomaxillaryfracture

○

Injuressphenoparietalvenoussinus

Hematomaaccumulatesatanteriortipofmiddlecranialfossa

Limitedanatomically(laterallybysphenotemporalsuture, mediallybyorbitalfissure)

Benignclinicalcourse

ClivalEDH

• Mostcommon=childwithneckinjury

○

Maycausemultiplecranialneuropathies(CNVImostcommon)

Hyperdensecollectionunderclivaldura

Limitedbytightattachmentofduratobasisphenoid,tectorial membrane

Usuallybenigncourse,resolvesspontaneously

ManagementofaclivalEDHisdictatedbyseverityandprogressionofthe neurologicdeficitsandstabilityoftheatlantoaxialjoint.Inpatientswith

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PrimaryEffectsofCNSTrauma

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(2-25)Graphicdepicts benignanteriortemporal epiduralhematoma. Fractureﬅdisruptsthe sphenoparietalsinus﬉. Low-pressurevenousEDH ﬊isanatomicallylimited, mediallybytheorbital fissureﬆandlaterallyby thesphenotemporal suture﬈.(2-26A)Axial NECTina33ymanwith headtraumashowsa biconvexanterior temporalacuteepidural hematoma﬇. https://t.me/ebookers

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(2-26B)AxialboneCTin thesamecaseshowsa fracturethroughtheright greatersphenoidwingﬅ. (2-26C)CTvenogramin thesamecaseshowsa displaced,lacerated sphenoparietalsinuswith contrastextravasation ("spotsign")ﬆ.Notethe EDHislimitedmediallyby theorbitalfissure﬈.The patientwastreated nonsurgically.TheEDH showednofurther enlargementandresolved completely.

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(2-27A)AxialCTAina childwithcraniovertebral junctiontraumashowsa smallclivalEDH﬈.There wasnoevidencefor vascularinjury.(2-27B) SagittalCTAreformatted fromtheaxialsourcedate nicelydemonstratesthe clivalepiduralhematoma ﬈.

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(2-28)Graphicdepictscrescent-shapedacuteSDH ﬆwithcontusionsand"contre-coup"injuries﬈, diffuseaxonalinjuries﬉.

minorcranialnerveinvolvement,theclinicalcourseisusuallybenign,and treatmentwithacervicalcollaristypical.

NECTscansshowahyperdensecollectionbetweentheclivusandtectorial membrane.SagittalMRofthecraniocervicaljunctionshowsthehematoma elevatingtheclivalduraandextendinginferiorlybetweenthebasisphenoid andtectorialmembraneanteriortothemedulla.

AcuteSubduralHematoma

Acutesubduralhematomas(aSDHs)areoneoftheleadingcausesofdeath anddisabilityinpatientswithseveretraumaticbraininjury.SDHsaremuch morecommonthanEDHs.Mostdonotoccurasisolatedinjuries;thevast majorityofSDHsareassociatedwithtraumaticsubarachnoidhemorrhage (tSAH)aswellassignificantparenchymalinjuriessuchascorticalcontusions, brainlacerations,anddiffuseaxonalinjuries.

Terminology

AnaSDHisacollectionofacutebloodproductsthatliesinorbetweenthe innerbordercelllayeroftheduraandthearachnoid (2-28)

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Etiology

TraumaisthemostcommoncauseofaSDH.Bothdirectblowstothehead andnonimpactinjuriesmayresultinformationofanaSDH.Tearingof bridgingcorticalveinsastheycrossthesubduralspacetoenteradural venoussinus(usuallythesuperiorsagittalsinus)isthemostcommon etiology.Corticalveinlacerationscanoccurwitheitheraskullfractureorthe suddenchangesinvelocityandbrainrotationthatoccurduringnonimpact closedheadinjury.

Bloodfromrupturedvesselsspreadsquicklythroughthepotentialspace betweentheduraandthearachnoid.LargeSDHsmayspreadoveranentire hemisphere,extendingintotheinterhemisphericfissureandalongthe tentorium.

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(2-29)AcuteSDHspreadsoverlefthemisphere ﬅ,alongtentorium﬇,intointerhemispheric fissureﬆbutdoesnotcrossmidline.

TearingofcorticalarteriesfromaskullfracturemayalsogiverisetoanaSDH. Thearachnoiditselfmayalsotear,creatingapathwayforleakageofCSFinto thesubduralspace,resultinginadmixtureofbothbloodandCSF.

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(2-30)NECTscanshowsthatsmallSDHﬅis easiertoseewithwider(R)comparedwith standard(L)windows.

LesscommoncausesofaSDHincludeaneurysmrupture,skull/duraarachnoidmetastasesfromvascularextracranialprimaryneoplasms,and spontaneoushemorrhageinpatientswithseverecoagulopathy.

Rarely,anacutespontaneousSDHofarterialoriginoccursinsomeone withoutanytraumatichistoryorvascularanomaly.Thesepatientsusually havesuddenseriousdisturbanceofconsciousnessandhaveapooroutcome unlesstheaSDHisrecognizedandtreatedpromptly.

Pathology

GrossPathology.ThegrossappearanceofanaSDHisthatofasoft,purplish, "currantjelly"clotbeneathatensebulgingdura.Morethan95%are supratentorial.MostaSDHsspreaddiffuselyovertheaffectedhemisphere andarethereforetypicallycrescent-shaped.

ClinicalIssues

Epidemiology.AnaSDHisthesecondmostcommonextraaxialhematoma, exceededonlybytSAH.AnaSDHisfoundin10-20%ofallpatientswithhead injuryandisobservedin30%ofautopsiedfatalinjuries.

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PrimaryEffectsofCNSTrauma

Demographics.AnaSDHmayoccuratanyagefrominfancytotheelderly. Thereisnosexpredilection.

Presentation.Evenrelativelyminorheadtrauma,especiallyinelderly patientswhoareoftenanticoagulated,mayresultinanaSDH.Insuch patients,adefinitehistoryoftraumamaybelacking.

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Clinicalfindingsvaryfromnonetolossofconsciousnessandcoma.Most patientswithaSDHshavelowGCSsonadmission.Delayeddeterioration, especiallyinelderlyanticoagulatedpatients,iscommon.

NaturalHistory.AnaSDHmayremainstable,growslowly,orrapidly increaseinsize,causingmasseffectandsecondarybrainherniations. Prognosisvarieswithhematomathickness,midlineshift,andthepresenceof associatedparenchymalinjuries.AnaSDHthatisthickerthan2centimeters correlateswithpooroutcome(35-90%mortality).AnaSDHthatoccupies morethan10%ofthetotalavailableintracranialvolumeisusuallylethal.

TreatmentOptions.ThemajorityofpatientswithsmallSDHsareinitially treatedconservativelywithcloseclinicalobservationandfollow-upimaging. Approximately6-7%ofthesedemonstrateanincreaseinSDHsizeovertime andeventuallyrequiresurgicalintervention.

CoronalgraphicdepictsthinaSDHlayering alongthetentoriumandinferiorfalxcerebri﬈.

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PatientswithlargerSDHs,alesionlocatedattheconvexity,alcoholabuse, andrepetitivefallsareatthegreatestriskfordeterioration.Surveillancewith follow-upCTscansisrecommendeduntiltheSDHresolvesoratleastupto5 weeksfollowingtheinitialtrauma.

Imaging

GeneralFeatures.TheclassicfindingofanaSDHisasupratentorialcrescentshapedextraaxialcollectionthatdisplacesthegray-whitematterinterface medially.SDHsaretypicallymoreextensivethanEDHs,easilyspreading alongthefalx,tentorium,andaroundtheanteriorandmiddlefossafloors (2-29).SDHsmaycrosssuturelinesbutgenerallydonotcrossdural attachments.BilateralSDHsoccurin15%ofcases."Contre-coup"injuries suchascontusionofthecontralateralhemispherearecommon.

Bothstandardsofttissueandintermediate("subdural")windowsaswellas bonealgorithmreconstructionsshouldbeusedinalltraumapatients,as small,subtleaSDHscanbeobscuredbythedensityoftheoverlyingcalvaria (2-30).Coronalandsagittalreformattedimagesusingtheaxialsourcedate areespeciallyhelpfulinvisualizingsmall("smear")peritentorialand parafalcineaSDHs (2-31) (2-32)

CTFindings

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NECT.Approximately60%ofaSDHsarehyperdenseonNECTscans (2-29). Mixed-attenuationlesionsarefoundin40%ofcases.Pocketsofhypodensity withinalargerhyperdenseaSDHusuallyindicaterapidbleeding (2-33) (234)."Dots"or"lines"ofCSFtrappedwithincompressed,displacedsulciare oftenseenunderlyinganaSDH.

MasseffectwithanaSDHiscommonandexpected.Subfalcineherniation shouldbeproportionatetothesizeofthesubduralcollection.However,if thedifferencebetweenthemidlineshiftandthicknessofthehematoma is3mmormore,thenmortalityisveryhigh.Thisdiscrepancyoccurswhen underlyingcerebraledemaistriggeredbythetraumaticevent.Early recognitionandaggressivetreatmentforpotentiallycatastrophicbrain swellingareessential (2-35)

Inothercases,especiallyinpatientswithrepeatedheadinjury,severebrain swellingwithunilateralhemispherevascularengorgementoccursvery

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(2-32B)Sagittalscansinthesamecaseshowthe rightperitentorialaSDH(top)withnormalleft sagittaldura(bottom)forcomparison.

(2-32A)ReformattedcoronalNECTscanusingthe axialsourcedateshowsasmallright peritentorialaSDHﬅ.

(2-31)

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Trauma

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quickly.Herethemasseffectisgreatlydisproportionatetothe sizeoftheSDH,whichmayberelativelysmall.

Occasionally,anaSDHisnearlyisodensewiththeunderlying cortex.Thisunusualappearanceisfoundinextremelyanemic patients(Hgbunder8-10g/dL) (2-36)andsometimesoccurs inpatientswithcoagulopathy.Inrarecases,CSFleakage throughatornarachnoidmaymixwith—anddilute—the acutebloodthatcollectsinthesubduralspace.

CECT.CECTscansarehelpfulindetectingsmallisodense aSDHs.Thenormallyenhancingcorticalveinsaredisplaced inwardbytheextraaxialfluidcollection.

PerfusionCT.CTorxenonperfusionscansmaydemonstrate decreasedcerebralbloodflow(CBF)andlowperfusion pressure,whichisoneofthereasonsforthehighmortality rateofpatientswithaSDHs.Thecortexunderlyingan evacuatedaSDHmayshowhyperemicchangeswithelevated

rCBFvalues.Persistinghyperemiahasbeenassociatedwith pooroutcome.

MRFindings.MRscansarerarelyobtainedinacutelybraininjuredpatients.Insuchcases,aSDHsappearisointenseon T1WIandhypointenseonT2WI.SignalintensityonFLAIR scansisusuallyiso-tohyperintensecomparedwithCSFbut hypointensecomparedwiththeadjacentbrain.aSDHsare hypointenseonT2*scans.

DWIshowsheterogeneoussignalwithinthehematomabut mayshowpatchyfociofrestricteddiffusioninthecortex underlyingtheaSDH.

Angiography.CTAmaybeusefulinvisualizingacorticalvessel thatisactivelybleedingintothesubduralspace.

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(2-33)(L)InitialNECTin ananticoagulatedmale patientshowsasmall mixed-densitySDH.(R) Scan6hourslatershows expanding,actively bleedingaSDH.(2-34) NECTscanshowsa55y manwithanactively hemorrhagingaSDH. Someclottedbloodis presentﬅ,butmuchof thehematomaconsistsof isodenseunclotted hemorrhage﬇.

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(2-35)NECTshowsa mixed-density12-mm aSDH﬊witha disproportionatelylarge subfalcineherniationof thelateralventricles(17 mm),indicatingthat diffuseholohemispheric brainswellingispresent. Subfalcineherniation≥3 mmportendsapoor prognosis.(2-36)NECT scaninaveryanemic patientshowsanisodense aSDH﬈.TheaSDHis almostexactlythesame densityastheunderlying cortex.Thegray-white interfaceisdisplaced inward﬇.

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