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Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_186_библиотеки_им_акад_М_И_Перельмана

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☆
Symptoms
Hemorrhagicandischemicstrokesareclinicallyindistinguishable.Thetissueisdamagedeitherway, eitherfromablockedorrupturedbloodvessel,andtheconsequentneurologicdeficitswillbeidentical.
Sohowdoyoudistinguishbetweenhemorrhageandischemiainapatientpresentingwithnew,acute­onsetfocalsymptoms?Easy:getaCTscan.EverysinglestrokepatientneedsaCT,becausetheCTisthe onlywaytoknowforsure.
Priortoimaging,youshouldsuspectischemicstrokebasedonthenumbersalone(remember,over85% ofstrokesareischemic),withonlytwoexceptions.Thesearenothard-and-fastrules,onlytip-offsto makeyouthinkofhemorrhageinsteadofischemia:
Worst headache of life. Patients who present with “the worst headache of my life” have a subarachnoidhemorrhageuntilprovenotherwise(seepage81).  Decreased level of alertness. This is nearly always seen with large bleeds, presumably due to elevated intracranial pressure and subsequent diffuse compression of the RAS, the network of thalamicandbrainstemneuronsthatmediatearousalandalertness.Ischemicstrokesthataffectthese RASneuronscanalsocauseadecreasedlevelofconsciousness,butthemajorityofischemicstrokes —eventhereallybigones—donot,andpatientsareusuallywideawake.Basilarstrokesarethebig exception;seepage66.
Box2.14IschemicStrokeandAlteredLevelofConsciousness
Therearethreeischemicstrokelocationsthatcanresultinalteredconsciousness:the thalamus,brainstem,andbilateralcerebralhemispheres.Strokesthataffectthethalamusor
brainstemcandoitasaresultofdirectdamagetothereticularactivatingsystem(RAS). Bilateralhemisphericstrokes—ofteninthesettingofanembolicshower,whentinyemboli
areshotupfromtheheartandscatterintothecerebralcirculation—canalsoberesponsible. Finally,anybigstrokethatswells,causingmidlineshift,ventricularcompression,and elevatedintracranialpressurewillalsocauseadecreasedlevelofconsciousnessviathe samepathophysiologicmechanismaslargebleeds.
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Adiffusion-weightedimaging(DWI)MRIsequenceshowingnumerousbilateral,embolic-appearing strokes.(ModifiedfromAtlasSW.MagneticResonanceImagingoftheBrainandSpine.5thed. WoltersKluwer;2016.)
Bothischemicandhemorrhagicstrokecan,andoftendo,presentwithelevatedbloodpressure.Inthe settingofischemia,thisistheresultofthebody’sattempttokeeppumpingbloodtothedeadordying oxygen-deprivedbraintissue(aphenomenoncolloquiallyknownas“auto-pressing”).Inthesettingof hemorrhage,acutehypertensionisoftenthecause,nottheconsequence,ofthestroke.
Etiology
ThemajorityofICHsaretheresultofuncontrolledhypertensionwhichovertimecanleadtothe formationoftinyCharcot-Bouchardaneurysmsthatarepronetorupture.Thebloodvesselsthatare affectedaregenerallythesameasthoseaffectedbysmallvesselocclusivediseasethatcauseslacunar infarcts.Thus,withonenotableexception,hypertensivehemorrhagestendtooccurinthesameanatomic locationsaslacunarinfarcts:thebasalganglia,internalcapsule,thalamus,andpons.
Themajorexceptionisthecerebellum,whichisnotaffectedbylacunarinfarctsbutiscommonly affectedbyhypertensivebleeds.Cerebellarhemorrhagesusuallypresentwithoccipitalheadache,nausea, vomiting,vertigo,andgaitdysfunctionduetoataxia.Direction-changingnystagmusanddysmetriaare oftenpresentonexamination.
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ACTofapatientwithacerebellarhemorrhageandsurroundingedemacausingcompleteeffacementof thefourthventricle(arrow)anddevelopinghydrocephalusofthelateralandthirdventricles.(Reprintedfrom BillerJ.PracticalNeurology.5thed.WoltersKluwer;2017.)
OtherlesscommonbutimportantcausesofICHinclude:
Cerebralvascularmalformations
Arteriovenous malformations (AVMs) account for nearlyhalf of ICHs in patients younger than 40. AVMs are tangles of intraparenchymalarteriesandveinsthatlackthenormalinterveningcapillarybed.Theresultisthatarterialpressuresaredirectly transmittedtovenous structures,causingincreasedbloodflow,venousdilation, and, ultimately,ICH. Theycanbevisualized on MRI but are best diagnosed by cerebral angiography. Treatment, when indicated, is with surgical resection or stereotactic radiosurgery. Cavernousmalformationsarecomposedofclustersofabnormalbloodvesselswithdefectiveandleakytightjunctions.Unlike AVMs, these are best diagnosed on MRI (they are often described as “popcorn”-like, with varying intensities reflecting thrombosis,blood,andcalcification);becauseofminimalbloodflow,theyareoftenmissedonangiography.Ifsymptomatic,these canbetreatedsurgically.
Cerebral amyloid angiopathy (CAA). CAA is due to amyloid depositionwithin thewalls of the cerebral vessels, causing weakening, degeneration, and predisposition to rupture. The amyloid
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materialisbiochemicallysimilartothatcomprisingtheplaquesassociatedwithAlzheimerdisease, but the two diseases are notinextricablylinked; although they frequently coexist, it’s possible to haveCAA withoutAlzheimerdisease andviceversa. Thebleedsassociatedwith CAAtend tobe cortical(asopposedtothe subcorticalanddeepgraymatterbleedsassociatedwithhypertension). Age is the most important riskfactor;CAAis uncommon inpatients under the age of50, andthe incidence rises with each decade thereafter. Because of the high rate of recurrent bleeding, it is preferabletokeepthesepatientsoffanticoagulationandantiplateletagentsifpossible.  Inflammatory and infectious conditions. Vasculitis (see page 88) and encephalitis (most often associated with herpes simplex virus) can both cause ICH. ICH is also a relatively common complicationofendocarditis,duetosepticemboliorrupturedmycoticaneurysms. Braintumors.Anybraintumorcanbleed.Themostcommonbraintumorsinadultsaremetastases: thoseassociatedwiththehighestriskofhemorrhagearemetastasesfromrenalcellcarcinoma,lung carcinoma,melanoma,thyroidcarcinoma,andchoriocarcinoma(seeChapter16). Bleedingdiathesis.Commoncausesincludeseverethrombocytopeniaassociatedwithhematologic malignanciesandhepaticfailure,iatrogeniccoagulopathyduetoanticoagulation,anddisseminated intravascularcoagulation (DIC). Thesepatients canbleed spontaneously, withoutany underlying brainpathology. Illicitdrugs.Cocaineandmethamphetaminesarethemostcommonculprits. Headtrauma.
Management
EmergentmanagementofacuteICHisrelativelystraightforward:controlthepatient’sbloodpressureto preventfurtherbleeding;consideranticoagulantreversalifthepatientistakinganysuchmedication; repeatheadimaging(typicallydoneat6-hourintervals)untilyouconfirmthatthebleedisnolonger expanding;andconsidersurgicalinterventionasneeded.AngiographyandMRImaybeindicated(usually nonurgently)tohelpdeterminethecauseofthebleed.
Anticoagula nt/Antithrombotic ReversalAgents
Heparin Protaminesulfate Enoxaparin Protaminesulfate Warfarin 4-factorprothrombincomplexconcentrate(PCC),vitaminK Directthrombininhibitors(dabigatran) Idarucizumab Directoralanticoagulants(apixaban,rivaroxaban) 4-factorPCC,andexanetalfa Aspirin Desmopressin(DDAVP)
Commonanticoagulants/antithromboticsandtheirreversalagents.Afewthingstonote.(1)AndexanetalfaisabiologicXadecoy thatbindsandinhibitsthedirectoralanticoagulants.ItwasFDA-approvedin2018forreversalofapixabanandrivaroxabanin patientswithuncontrolledorlife-threateningbleeding,butitsuseremainslimitedduetolackofrandomizedclinicaltrialdataas wellasitshighcost.Large-scalerandomizedtrialsareongoing.(2)Giventhataspirinactsasanantiplateletagent,onewould thinkthatreversalwithplatelettransfusionwouldmakesense.However,platelettransfusionshavenotbeenshowntoimprove outcomes(andactuallymayworsenthem).Asaresult,platelettransfusionsaretypicallyreservedonlyforpatientsonaspirinfor whomaneurosurgicalprocedureisplanned.
Patientswithbighemisphericbleeds,bleedsthatentertheCSFspaces(i.e.,intraventricular hemorrhageinwhichbloodcanclogupthearachnoidgranulationsandpreventCSFreabsorption)and posteriorfossableeds(theposteriorfossaisthemostconfinedplaceintheskullandhasaverylimited abilitytoaccommodateadditionalvolume)areallathighriskofdevelopingelevatedintracranial pressureandherniation.ThesepatientsshouldbeadmittedtoanICUandconsideredforsurgical intervention,usuallywitheitheranexternalventriculardrainorcraniectomy.
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Computerizedtomography(CT)scanofanintracerebralhemorrhage(ICH)pre-andpost-decompressive hemicraniectomy.(ModifiedfromLouisED,MayerSA,NobleJM.Merritt’sNeurology.14thed.Wolters Kluwer;2021.)
SubarachnoidHemorrhage(SAH)
SAH—bleedingwithinthespacebetweenthepiaandarachnoidmembranes—accountsforapproximately 3%ofallstrokes.Itisalife-threateningevent.ThemajorityofnontraumaticSAHsareduetoruptured saccular(or“berry”)aneurysms,whichofteninvolvethecircleofWillisarteriesatthebaseofthebrain (theanteriorcommunicatingarteryisthemostfrequentlocation).Arterialdissections,AVMs,cocaine use,andprettymuchanyoftheothercausesofICHlistedabovecancauseSAHaswell.
Themostcommonmodifiableriskfactorsincludehypertension,cigarettesmoking,andheavyalcohol use.Femalesareslightlymoreatriskthanmales.
Mortalityratesarehigh.Anestimated15%ofpatientswilldiebeforereachingthehospital,and approximately25%willdiewithin24hoursofaneurysmrupture.
Presentation
ThetextbookpresentationofSAHisathunderclapheadache,definedasheadachethatreachesmaximal intensityinunderaminute(seepage94).Inreality,onlyapproximately20%ofpatientswithSAHpresent withathunderclapheadache,butnearly100%reportthe“worstheadacheofmylife.”Severity,then,and notacuityofonset,iskey.Somepatientswillreportahistoryofapriorsevereheadache,usually occurringwithintheprecedingfewdays.Thesearereferredtoassentinelheadachesandarethoughtto representminor,low-volumeaneurysmalleaks.Recognizingthemcanbelifesaving.Othersymptomscan include:
Nausea, vomiting, and neck pain or neck stiffness (due to meningeal irritation caused by the
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breakdownofbloodproductswithintheCSF) Focal neurologic symptoms (these will dependon where the aneurysm is located, but the classic finding is a pupil-involving CN3 palsy due to compression of the nerve by a posterior communicatingarteryaneurysm) Preretinalhemorrhages(knownasTersonsyndrome,theseportendapoorerprognosis)
Diagnosis
ACToftheheadisextremelysensitiveifperformedwithinthefirst6hoursofthesubarachnoidbleed. Thesensitivitythendropswitheachpassinghour,fallingtoonly∼50%by1weekout.IftheCTofthe headisnegative—beyond6hoursorevenwithin6hours,ifclinicalsuspicionishigh—alumbarpuncture mustbeperformed.Youarelookingforredbloodcellsthatdonotdilutefromtube1ofcollectedCSFto tube4(dilutionismoresuggestiveofatraumatictap),pleocytosis(elevatedwhitebloodcellswithinthe CSF;bloodisirritatingandcancauseachemicalmeningitis,hencetheelevatedwhitecount),and xanthochromia(ayellowishcolorduetobilirubinreleasedfromredbloodcellbreakdown;thiscanbe confirmedvisuallybutismoreaccuratelyidentifiedbyspectrophotometrytechniquesinthelaboratory).
IftheCTand/orCSFanalysisarepositive,vesselimaging(withCTangiographyor,ifneeded,digital subtractionangiography)isindicatedtodeterminethepresenceofananeurysm.
TheclassicappearanceofsubarachnoidhemorrhageonCTscanispooledbloodwithinthebasilar cisterns(includingthesylvian,ambient,quadrigeminalandinterpeduncularcisterns—don’tworryabout thesenames;we’veincludedthemasareference,andsoyou’llrecognizethemifandwhenyouhear themmentioned)atthebaseofthebrain(A).Thebloodcanthenspreadintothesubarachnoidspacesof thecorticalsulci(B;whitearrowsarepointingtobloodwithinthesulci).(A,modifiedfromHainesDE.
NeuroanatomyAtlasinClinicalContext.10thed.WoltersKluwer;2018.B,reprintedfromMansoorA. FrameworksforInternalMedicine.WoltersKluwer;2018.)
TreatmentandComplications
PatientsshouldbeadmittedtoanICU,becausebothmedicalandneurologiccomplicationsarecommon.
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Ifananeurysmisfound,earlyrepairwitheitherendovascularcoilingorclippingisthestandardofcare.
Theriskofaneurysmalrebleedingishighestwithinthefirst24hoursaftersymptomonset.Vasospasm, thoughttobeduetospasmogenicsubstancesgeneratedduringthebreakdownofblood,isanotherearly complication,althoughthehighestriskperiodisabitlater,usuallycitedasbetweendays4and14.To reducetheriskofvasospasm,allpatientsshouldreceivenimodipine(acalciumchannelblocker)for 21days,andeuvolemiashouldbemaintained.TranscranialDopplerstudies(whicharedonebedside,and candetectincreasedvelocityofflowwithintheACAandMCA,whichissuggestiveofspasm)and angiographicimagingarediagnosticofvasospasm.Treatmentisaggressive,withbloodpressure augmentation(viafluidsorvasopressors)and,ifneeded,endovascularinterventionwitheitherintra­arterialadministrationofvasodilatorsorballoonangioplasty.
HydrocephalusduetoobstructionofCSFreabsorptionbybloodisanothercomplication,andoften requiresplacementofanexternalventriculardrain.
Seizuresoccurin5%to15%ofpatients.Althoughtheidealdurationoftherapycontinuestobe debated,mostpatientsreceiveseizureprophylaxisforseveraldaysfollowingtheirbleed.
Medicalcomplicationsincludehyponatremia(thoughttobemediatedbyhypothalamicinjurycausing eitherthesyndromeofinappropriateantidiuretichormonesecretion[SIADH]orcerebralsaltwasting), fevers,andcardiacabnormalitiesincludingelectrocardiogram(ECG)changes(mostoftenSTsegment depression,deepTwaveinversions,andprominentUwaves,butcanalsoincludeventricularfibrillation withcardiacarrest),troponinleaks,andleftventriculardysfunction(oftencharacterizedbyapical ballooningthatmimicsmyocardialinfarctionwithSTsegmentelevationontheECGthatlooksjustlikea typicalmyocardialinfarction;catheterization,however,willrevealcleancoronaryarteries—this conditionisknownastakotsubo,orstress,cardiomyopathy).
Box2.15SubduralandEpiduralHematomas
Subduralandepiduralhematomasarenottypicallyclassifiedas“strokes”becausethey causefocalneurologicsymptomsbycompressiononly;thatis,theblooditselfdoesnot contactbraintissue.Nonetheless,theyareimportantanddeserveaquickreviewhere.
Subduralhematomasformbetweentheduraandarachnoidmembranes.Theyresultfrom ruptureofthebridgingveinsthatdrainfromthesurfaceofthebrainintotheduralvenous sinuses.Subduralsaregenerallyseenintwosettings:inyoungpatients,followingacute shearingtraumaorwhiplashinjury,andinelderlypatients(oranyonewithsignificantcerebral atrophy,includingalcoholics).Evenseeminglytrivialheadinjury—withoutheadimpact—can causesubduralbleedsintheelderly.Symptomsaredependentonthelocationandextentof thebleedandcanincludeheadache,encephalopathy,andfocaldeficitsduetomasseffect and/orelevatedintracranialpressure.Treatmentissupportiveunlessthereissignificant masseffectwithmidlineshift,inwhichcasesurgicalinterventionmaybeindicated.
Epiduralhematomasformwithinthepotentialspacebetweentheskullandtheduraandare mostoftenduetoruptureofthemiddlemeningealartery.Theclassicpresentationisoneof a“lucidinterval”followedbyprogressiveneurologicdeclineintocoma;butagain,patients canpresentwithalmostanything(includingheadache,decliningmentalstatus,andfocal deficits)dependingonthelocationandextentofthebleed.Surgicaltreatmentismore
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commonthanwithsubduralbleeds,giventheproclivityofepiduralbleedstowardrapid expansion(remember,epiduralbleedsarearterialbleeds).Endovasculartreatments, includingembolizationofthemiddlemeningealartery,arebecomingincreasinglywidespread.
Epiduralbleeds(A)usuallyappearconvexbecausetheyareboundbytheskull’ssuturelines(wherethe durafirmlyattachestotheskull).Subduralbleeds(B)cancrosssuturelinesandappearconcaveon imaging.(ModifiedfromHainesDE.NeuroanatomyAtlasinClinicalContext.10thed.WoltersKluwer;
2018.)
AFewOtherCerebrovascularDisorderstoKnow
Entirechapterscouldbededicatedtoeachofthefollowingtopics,butwewillsummarizethesalient featuresofthesedisordersasconciselyaswecan.
CervicocephalicArterialDissection
Thetermdissectionreferstoatearintheintimalliningofanartery.Themostimportantthingtokeepin mindwithcervicocephalicdissection(dissectioninvolvingvesselsintheneckandhead)isthat, somewhatcounterintuitively,thebiggestconcernisnotbleedingbutthrombosisandembolism.Blood collectsbetweenlayersofthevesselwall,andthesubsequentlyalteredpatternofbloodflowand exposureofthrombogenicsubendothelialmaterialtocirculatingbloodpredisposestointramuralclot formation.Theclotcantheneitherobstructbloodflowinsituorembolizetoblockmoredistalvessels.
Theinternalcarotidandvertebralarteriesaremostcommonlyaffected.Minortrauma(suchassports injuriesandinexperiencedchiropracticmanipulation)andpredisposinggeneticconditions(fibromuscular dysplasia,Ehlers-Danlossyndrome,Marfansyndrome,andautosomaldominantpolycystickidney
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disease)arethemostcommoncauses.
Carotiddissectionisusuallyextracranial,occurringnearthebaseofthebrain,butcanbeintracranial aswell.Headacheisthemostcommonpresentingsymptom,classicallyretro-orbitalandipsilateraltothe dissectedartery.Hornersyndrome(duetoinvolvementofthesympatheticnervesrunningonthesurfaceof theartery,seepage310),retinalarteryocclusionoramaurosisfugax(temporarylossofvision),and anteriorcirculationstrokescanalsooccur(duetothrombusformationandembolization).
Vertebraldissectionisalsomostoftenextracranial,typicallyaroundtheC1-C2vertebrae,wherethe vertebralarteriesaremostmobileandleastprotected.Occipitalheadacheorposteriorneckacheare common,asarefocaldeficitsduetobrainstemandcerebellarischemia.
Angiographyisdiagnosticandcandemonstrateanintimalflap,doublelumen,andalong,tapered­appearingarterialstenosisorocclusion(referredtoasthe“flame”sign).Treatmentiswitheither antiplateletoranticoagulanttherapy(thebestoptionremainsdebatable,andthedecisionwilldependon thespecificcircumstancesofthepatient).Treatmentistypicallycontinuedforseveralmonthsatthevery leastuntilfollow-upimagingdemonstrateshealingorresolutionofthetear.
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