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Ростовский Государственный Медицинский Университет

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Медицина общая

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Книга_186_библиотеки_им_акад_М_И_Перельмана

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tonsillarherniationareoftenmissedbecausethereareusuallynopupillarychangesonexamination. Instead,headache,neckstiffnessandincreasingsomnolencearefollowedbyextensorposturing, respiratoryfailure,anddevastatingcirculatorycollapse.

Tonsillarherniation.Thearrowpointstothedownwarddisplacementofthecerebellartonsils.(Modifiedfrom NelsonLB,OlitskySE.Harley’sPediatricOphthalmology.6thed.WoltersKluwer;2013.)

BrainDeath

Braindeathisdefinedasthecompleteandirreversibleabsenceofallcerebralandbrainstemfunction.It isnearlyuniversallyconsideredsynonymouswithdeath,butthediagnosiscanbechallenging,as protocolsanddefinitionsvaryfromcountrytocountryandevenfromhospitaltohospital.Togiveyouan ideaoftherequirementsneededtodeclareapatient“braindead,”hereisanexampleofbraindeath guidelinesfromastatementissuedbyahospitalinNewYorkCity:

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Clinicalrequirements:

ClinicalorradiographicevidenceofacuteCNSinjurythatexplainsthebraindeadstate The absence of any confounding factors, including medications that depress brain function, neuromuscular blocking agents, hypothermia,hypotension,andothermetabolicderangements

Neurologicexaminationrequirements:

Thepatientiscomatose Thepatienthasnobrainstemreflexes(seepage427) Thepatienthasnomotorresponsetopain

Apositiveapneatest:

Theapneatestisperformedafter alloftheabovecriteria have beenmet.Thegoal is toprove theabsenceofthebrainstemmediatedrespiratoryresponse(i.e.,nospontaneousbreathing)despiteintensestimulationtobreathe(Paco2>60mmHg)

Tripleflexionresponse(seefootnotebelow).

Ifsomeoftheabovecriteriacannotbeadequatelyperformedorassessed,confirmatorytestscanhelp establishthediagnosis.AnEEG,forexample,willshowacompleteabsenceofcerebralelectrical activity,includingalackofreactivitytoexternalstimulation.Angiographywillusuallyshowabsenceof bloodflowwithintheintracranialarteries.

Therearenoknownreportsofneurologicrecoveryafteraconfirmeddiagnosisofbraindeath.

Box14.5ComaandPersistentVegetativeState

Thereisadifferencebetweencomaandpersistentvegetativestate.Comaisastateof unarousableunresponsiveness.Acomatosepatientwillnotarouseevenwithstrongand continuousstimuliandcannotinanymeaningfulwayinteractwiththeenvironment.

Persistentvegetativestateisastateofwakefulnesswithoutawareness.Patientsshowno awarenessofthemselvesoroftheirenvironment.Theydemonstratenopurposeful movementoranyevidenceoflanguagecomprehensionorexpression.However,theyoften maintainnormalsleep/wakecycles,andbothbrainstemandspinalreflexesmaybe

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preserved.Guidelinesvary,butpersistentvegetativestateisgenerallydeemedpermanent after3monthsto1year,dependingontheetiology.Meaningfulrecoveryafterthispointis rare.

Box14.6Post-ArrestPrognostication

Oneofthemoredifficultjobsofaneurologististohelpestablishapatient’sprognosis followingacardiacarrest.VariousotherICUteamsoftenaskforassistanceindetermininga patient’schanceofneurologicrecovery,becausehavingasenseofapatient’sprognosiswill helpguidesubsequentmanagement.Andfamilies,ofcourse,wantanswersassoonas possible:Willmymother/father/spouse/partnersurvive?Andifso,whatwillthatsurvivallook like?

Unfortunately,thesequestionsareoftenhardtoanswer(theexceptionisbraindeath:if confirmed,weknowthepatientwillnotrecover).Theneurologicexaminationhasthebest prognosticvalue.Theabsenceofbrainstemreflexesandthelackofanypurposefulmotor responsetopainfulstimuliportendpoorly,suggestingalowlikelihoodofeverachieving functionalindependence.EEGandbrainimagingaregenerallylesshelpful:“malignant”EEG patterns(suchasburst-suppressionandsuppressionwithcontinuousperiodicdischarges) andlossofgray/whitedifferentiationonCTassociatedwithanoxicinjuryareconcerning,but uncommonlypatientscanstillrecover.Eveninthepresenceofapoorexamination(absent brainstemreflexesexceptforcornealreflexes,forinstance,andnomotorresponsetopain) andburst-suppressionEEG,wecanofferguidanceandhelppreparefamiliesforwhat’s likelyahead,butwecannotsayanythingforcertain.

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Burst-suppressionischaracterizedbyburstsofhigh-voltagesharpwavessuperimposedonan otherwisesuppressedbackgroundandisconsideredoneofthehighlymalignantEEGpatterns associatedwithapoorprognosis.(ReprintedfromSternJM.AtlasofEEGPatterns.2nded.Wolters Kluwer;2013.)

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Whitearrowspointtothesubduralblood.Asterisksmarkexamplesofherniation(in(A)subfalcine;in (B)uncal).TheblackarrowpointstoaDurethemorrhage.(ModifiedfromDaffnerRH,HartmanM. ClinicalRadiology.4thed.WoltersKluwer;2013.)

YourPatient’sFollow-up:Neha’sCTscanshowsanacuteleft-sidedsubduralhematoma

causingsignificantmidlineshifttotherightandbothsubfalcineanduncalherniation. BrainstemcompressionhasresultedinwhatisknownasaDurethemorrhagewithinthe pons—thesearesmall,linearbleedsthatareoftenassociatedwithuncalordownward herniation,likelyduetotornarterialbranchesorruptureddrainingveins.Themomentyou seethescan,youknowthebleedisdevastating;Neha’schancesofmeaningfulrecoveryare poor.Youstepoutsidetheimagingsuitetospeaktoherfamily,whoarewaitingforyouin thehallway.Herdaughterhasinhandhermother’sdo-not-resuscitate/do-not-intubate documentation,andthefamilyisinagreementthatNeha—afiercelyindependentwoman who,overthepastfewyears,hadrefusedtoaccepthelpfromahomehealthaideand resistedtheuseofawalker,despitemultiplefalls—wouldwantnoextraordinarymeasures taken.Sheisadmittedtothepalliativecareunitandstartedonamorphinedripforpain.She passesawaypeacefullyseveralhourslater.

Younowknow:

1. Howtodifferentiatevasogenicfromcytotoxicedema.Vasogenicedemaismostoftencausedbymasslesionsandhasacharacteristic

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finger-likeappearanceonCTthatpreservesthegray-whitematterborder.Cytotoxicedemaismostoftencausedbyacuteischemiaand blursthegray-whiteborderonCT.

2. WhentoclinicallysuspectelevatedICP(headache,nausea,vomiting,andworseningsomnolenceintheappropriateclinicalcontextare thebigtip-offs)andthefirststepsinthemanagementofacutelyelevatedICP.

3. How to recognize the major patterns of herniation—subfalcine, uncal, central, and tonsillar herniation—both clinically and radiographically.

4. That decorticate posturing, characterizedbyupperextremity flexioninto thechest andlower extremityextension, iscausedbybrain damage above the level of the red nucleus. Injury below the red nucleus can result in decerebrate posturing, which is clinically distinguishedfromdecorticateposturingbyextensionoftheupperextremities.

5. Howtothinkaboutbraindeathandthepotentialchallengesinvolvedinitsdiagnosis.

NormalICPisapproximately5to15mmHginasupineadult.

Itisimportanttonotethatspinalreflexescanpersistandappeartobevolitional.Thetripleflexionresponseisacommonexample, characterizedbyflexionofthefoot,leg,andthighinresponsetopainfulstimuliofthelowerextremity.Thisisastereotypedspinalreflex,nota voluntarywithdrawalresponse.

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AlteredMentalStatus

Inthischapter,youwilllearn:

1. Whatwemeanwhenwetalkaboutalteredmentalstatus(AMS)

2. Howtodifferentiateencephalopathyfromaphasia

3. Howtodistinguishprimaryneurologicfromsecondarycausesofalteredmentalstatus

4. The most common—and most dangerous—primary neurologic causes of altered mental statustowatchoutfor;wewillalsoprovideyouwithaquickbutcomprehensivereviewof toxic,metabolic,cardiac,andinfectioussecondarycausesofalteredmentalstatus,among others

CASE15

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YourPatient:Donald,an88-year-oldretiredschoolteacher,isbroughttotheemergency

departmentbyhiswife,whofoundhimslumpedoveronthetoiletseatearlythismorning.His eyeswereclosed,andhewasunresponsivetovocalorphysicalstimulation.Hehasa historyofhypertensionanddiabetes.Hewasalsodiagnosedwithaurinarytractinfection 3daysago,forwhichheisnowonantibiotics.Onarrivalatthehospital,heisstill unresponsive.Heisafebrile,andhisbloodpressureis110/75mmHg.Theemergency departmenttriagenursecallsastrokecodeforalteredmentalstatus,andyoumeetthe patientandhiswifeinthehallwayoutsideoftheCTscanner.What’sthenextstepinyour management?

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Alteredmentalstatus(AMS)isoneofthemostcommonchiefcomplaintsencounteredbyneurologists. ButwhatdoesitactuallymeanforapatienttohaveAMS?AMSisavaguecatch-alltermthatgenerally describespatientswhoaresomehow,insomeway,offtheircognitivebaseline.Itcanmeanconfused, disoriented,delirious,forgetful,somnolent,evencomatose.

Thefirststepinidentifyingtheproblemisdistinguishingprimarycentralnervoussystem(CNS)causes ofAMS—suchasseizure,encephalitis,orAlzheimerdisease—fromsecondarycauses—suchashypo-or hyperglycemia,systemicinfection,oruremia.

WesaidthisinChapter1butitbearsrepeating:thedistinctionbetweenneurologicandnon-neurologic causesofAMSisdifficult,sometimesevenimpossible,tomake.Ifthereisanynewfocalityon examination,assumethatthepatient’sAMSistheresultofaprimaryneurologiccauseuntilproven otherwise(anditwillsometimesbeprovenotherwise;forexample,inthesettingofhypo-and hyperglycemia,seepage377).If,afteracomprehensiveworkup,andevenintheabsenceoffocality,there isnoalternateexplanationforthepatient’sAMS—nometabolicderangement,nounderlyingsystemic infection—itwilllikelybeuptotheneurologisttofigureoutwhat’sgoingon.

BeforewedoaquickdiveintothemultifactorialcausesofAMS,thereisonecrucialdistinctionto make.

EncephalopathyVersusAphasia

LikeAMS,encephalopathyisavaguetermthatisoftendefinedasanysortof“brainmalfunctioning.” Notthemostusefuldefinition.Neurologiststhinkofanencephalopathicpatientasonewhoisglobally confused(deliriousisessentiallyasynonym;seeBox15.1);thetermcarriesconnotationsofnonneurologiccausesofAMS,suchasuremia,hepaticfailure,hypo-orhyperglycemia,illicitdrugortoxin ingestions(inthesecases,werefertoitasatoxic-metabolicencephalopathy).However,diffuse neurologicproblems—suchasencephalitisormultifocalscatteredcerebralinfarcts—canalsocause encephalopathy.

Box15.1Delirium

Theprecisedifferencebetweenencephalopathyanddeliriumishazy,andifyouask20 neurologists(aswedid),youwilllikelyget20differentanswers(aswedid!).Ingeneral, however,thetermencephalopathyisusedwhenthereissomesortofknownorsuspected underlyingpathology,beittoxic-metabolicorprimaryneurologic,whereasdeliriumisoften usedinthesettingofnoclear-cutcause(e.g.,todescribeanelderlypatientwhobecomes confused[or“sundowns”]overnight).Encephalopathycanalsorefertopatientswhoare comatose(e.g.,apatientwithend-stageliverfailurewhobecomesincreasinglysomnolent andultimatelyunresponsiveisdiagnosedwithhepaticencephalopathy),whereasdelirious patientsareconfusedbutawake.

Thehallmarkofanencephalopathicpatientwhoisawakeisinattention:thepatienttypicallyrequires frequentreorientationandredirection.If,forexample,anencephalopathicpatientisaskedtocount

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backwardfrom20,heorshemaygetto17andthendriftoff,starttalkingaboutsomethingentirely unrelatedorevenfallasleep,requiringrepeatedprompting,vocaland/orphysicalstimulationtocontinue tocount.Waxingandwaningsomnolenceanddisorientationarealsocommoncharacteristicsof encephalopathicpatients.

Aphasicpatientscanappeartobeencephalopathic,particularlythosewithaWernickeaphasia(see page59),whocannotfollowcommandsandwhosespeechoftensoundslikegibberish.Unlike encephalopathy,however,aphasiaisduetofocalneurologicdisease,strokebeingthemostcommon cause,nottomentionthemosturgenttorecognize.

Sohowcanyoudistinguishbetweenaphasiaandencephalopathy?Aphasicpatientsarenotusually inattentive.Theyaretypicallyfullyalertandoftenappearfrustratedbytheirinabilitytocommunicate. Dependingonthelocationofthelesion,theymayormaynotbeabletorepeat,followcommands,orname objects.Theywilloftenhaveotherfocaldeficits,includingweaknessandnumbness,onexam.Themore aphasicpatientsyouencounter,themoreeasilyyouwillbeabletorecognizeaphasia.Thebottomline, however,isthat,ifyouarenotsure—anditisoknottobesure,thisstuffishard!—callforhelp.Ifyou areinahospital,thatmaymeancallingastrokecode.Ifyouaccidentallymistakeencephalopathyfor aphasia,theworstthingyouhavedoneistakenupafewminutesofaneurologyresident’stime;ifyou mistakeaphasiaforencephalopathy,youmaymissanopportunitytotreatorabortastroke.

NeurologicCausesofAMS

Thefollowinglistisbynomeanscomprehensive,butitincludesthemostcommon—andmostimportant torecognize—primaryneurologiccausesofAMS.Eachitembelowhasbeenorwillbediscussedin depthelsewhereinthisbook.Thetakeawayisthattheseconditionsshouldbefrontandcenterwhenyou seeapatientwithAMS:theseconditionsarewhythepatientneedsaneurologist,anditisuptoyouto ruletheminorout.Howdoyoudothat?Obtainacarefulhistory(thisisoftenreliantoncollateral informationfromfamilymembersandcaretakers,aspatientswithAMSrarelywillbeabletoprovidethe mostmeticulousofhistories),performadetailedneurologicexamination,ruleoutalternativenonneurologicexplanations,andobtainrelevantlaboratoryworkandimagingwhenindicated.

Seizure(seeChapter6).Whatwereallymeanhereisthepostictalstate.Postictalstateismostoften characterizedbylethargyandconfusion,butagitationandpsychosiscanbepresentaswell.Patients canbepostictalforminutestohoursfollowingtheirseizure. Ischemic stroke(see Chapter 2). Remember, thevastmajorityofischemicstrokesdo notpresent with AMS. The big do-not-miss exception is a basilar artery occlusion; because of potential involvement ofthe reticular activatingsystem locatedinthethalamusandbrainstem,basilarartery occlusionscancausesomnolence,evencoma.Associatedoculomotorpalsies,visualfielddeficits, andvertigoarealsocommonlypresent. Hemorrhagicstroke (see Chapter 2). Unlikeischemic strokes, hemorrhagic strokes often present withadecreasedlevelofalertness,likelytheresultofelevatedintracranialpressureandsubsequent compressionofthereticularactivatingsystem.  CNS infection (see Chapter 8). Both encephalitis and meningitis can cause AMS. Because encephalitis affects the brain parenchyma, it can and often does cause both AMS and associated focaldeficits.Meningitisaffectsthepain-sensitivemeninges,andAMSinthesettingofmeningitisis generallyattributedtopainandlethargy.

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