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

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https://t.me/med1917
Follow-uponYourPatient:YouimmediatelysuspectthatSuzannehasParkinsondisease
becauseofhershufflinggaitandunilateralrestingtremor.Yourexaminationalsoreveals cogwheelrigidityinherrightupperextremityandapositivepulltest.Hercognitivetestingis normal.YoutellhershehasParkinsondiseaseanddiscussstartingtreatmentwith levodopa-carbidopa.Becausehersymptomsareinterferingwithherworkinthehospital, sheagreesandbeginstreatmentimmediately.Onemonthlaterinfollow-upshereportsthat themedicationhashelpedherimmenselyandshehasbeenabletocontinueworkingmuch asshehasbecomeaccustomedto.Youarrangetoseeheronaregularbasistomonitorher symptomsandmedication.
Younowknow:
1. HowtodiagnoseandtreatpatientswithParkinsondisease.
2. ThemnemonicTRAP(committhistomemory!)thatsummarizesthebasicmanifestationsofParkinsondisease.
3. Howtodistinguishbetweenthevarioustypesoftremor;inparticular,howtodifferentiatethetremorofParkinsondiseasefrombenign essentialtremor.
4. When to suspectthepresence ofatypicalparkinsoniandisorders,includingprogressive supranuclear palsy, corticobasaldegeneration, dementiawithLewybodies,andmultiplesystematrophy.
5. How to recognize and manage the most common hyperkinetic movement disorders, including choreiform disorders and Huntington disease,tardivedyskinesia,dystonia,myoclonus,ticdisordersandTourettesyndrome,andmovementdisordersofsleep.
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NeurocriticalCare
Inthischapter,youwilllearn:
1. How(andwhyitmatters)todistinguishvasogenicandcytotoxicedemaonbrainimaging
2. All about elevated intracranial pressure: what causesit, whento clinicallysuspectit, and howtoemergentlytreatit
3. Howtoclinicallyandradiographicallyrecognizethemajorpatternsofbrainherniation
4. Howtoconceptualizeanddiagnosebraindeath
CASE14
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Neha’sCTscan.(ModifiedfromDaffnerRH,HartmanM.ClinicalRadiology.4thed.WoltersKluwer;
2013.)
YourPatient:Neha,a93-year-oldmotheroffourandgrandmotherofeight,isbroughtto
thehospitalbyEMSafterherdaughterfoundherunconsciousonthefloor.Herblood pressureis180/100mmHgonarrival.Sheislargelyunresponsiveonexamination,arousing onlybrieflytopainfulstimuli.Whenyoulifthereyelids,younotethatherrightpupilis4mm andreactive,butherleftpupilisfixedanddilated.YourushhertoCTandobtaintheimages above.Whatisthenextstepinyourmanagement?
Neurointensivecareencompassesthemanagementoflife-threateningneurologicdiseases.Atthispointin thebookyouarealreadyfamiliarwiththemostcommonneurologicemergencies—acuteischemicand hemorrhagicstroke,subarachnoidhemorrhage,acutespinalcordcompression,statusepilepticus, myastheniccrisis,uncontrolledcerebralinfections,andtraumaticbraininjury—sowewon’tspendany moretimehereonthediagnosisandmanagementofthesespecificconditions.Instead,wewillstepback andfocusonafewoftheworst-casescenariosthatunfortunatelycanbethefinalcommonpathwaysof manyoftheabovepresentations.Theseinclude:
Cerebraledema Elevatedintracranialpressure Brainherniation Braindeath
Dedicatedneurologicalandneurosurgicalintensivecareunits(thefirstofwhichopeneditsdoorsin
1920)werecreatedwiththegoalsofearlyidentificationand—ifindicated—aggressivemanagementof
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thesecomplications.Sometimes,rapidinterventionresultsinremarkablerecovery;othertimes, interventionisunsuccessful,futile,orunderstandablydeclinedbythepatientorpatient’sfamily. Compassionateconversationwiththepatient(andpatient’sfamily,particularlyifthepatientisunableto participate),ofteninvolvingtrainedpalliativecarespecialists,cansometimesbethebestandmost meaningfulcareaneurologicalICUcanprovide.
Roundinginsideaneurointensivecareunit.Theteamisoftenabigoneandcanincludeanattending, fellow,residents,interns,nurses,physicianassistants,pharmacists,anddieticians,allworkingtogetherto helpcareforthesepatientswithlife-threateningcomplications.
CerebralEdema
Thetermedemareferstoanexcessoffluidwithinabodycompartmentorcavity.Thereareafewtypesof cerebraledemathatyoushouldknow,eachwithspecificetiologiesandimagingcharacteristics.
Vasogenicedemaiscausedbythebreakdownoftheblood-brainbarrier.Whenintact,theblood-brain barrierpreventsmanysubstancesthatcirculatewithinthebloodfromenteringintotheextracellularfluid oftheCNS.Whenthetightjunctionsoftheblood-brainbarrierbecomeleaky,fluidaccumulateswithinthe extracellularspaceofthebrain.Masslesionssuchasbraintumorsandabscessesarecommoncausesof vasogenicedema.Acuteischemiacausescytotoxicedema(seepage356)butovertime(withinhoursto days)cancausevasogenicedemaaswell.
Vasogenicedemahasacharacteristicfinger-likeappearanceonCT,spreadingwithinthewhitematter butsparingthegraymattercortex.Youcanthinkofitthisway:becausethewhitematterismadeupof axonsandthecortexismadeupoftightlypackedcellbodies,thereisspaceforextracellularfluidto
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spreadwithinthewhitematterbutnotwithinthetightlypackedcorticalregions.
Cytotoxicedemaistheresultofcelldeath.Itisusuallyduetothedepletionofintracellularadenosine triphosphate(ATP),disruptingthefunctionofthesodium/potassiumtransporterandcausingintracellular osmoleaccumulationand—becausewaterfollowstheosmolargradient—intracellularfluid accumulation.Acuteischemiaisthemostcommoncause;othercausesincludeacuteliverfailureand anoxicinjury.
Radiographically,cytotoxicedemaisoftensubtleonCT,appearingashypoattenuationandblurringof thegray-whitejunction.OnMRI,cytotoxicedemaisbestidentifiedondiffusion-weightedimaging(DWI) sequences.AsdiscussedinChapter2,intracellularfluidshiftsandsubsequentcellularswellingresultin restrictedwaterdiffusion,whichappearsbrightwhiteontheMRI.
CTscansshowing(A)vasogenicedema,whichhasacharacteristicfinger-likeappearanceandspares thegraymattercortex(whitearrowspointtothefinger-likeextensionsofsparedcortexthatare surroundedbyvasogenicedema),and(B)cytotoxicedema,whichobliteratesthegray-whitematter junction(whitearrowspointtotheedema).(ReprintedfromWeinerWJ,GoetzCG,ShinRK,LewisSL. NeurologyfortheNon-Neurologist,6thEdition.Philadelphia:WoltersKluwer,2010.)
Thesetwocategoriesarenotexclusive.Variousbrainlesionsandinjuries(forexample,intracerebral hemorrhageandtraumaticbraininjury)cancausebothcytotoxicandvasogenicedema.
Twoothertypesofcerebraledematobeawareofareinterstitialedema(alsoknownas transependymalorhydrostaticedema)andosmoticedema.
Interstitialedemaistheresultofobstructivehydrocephalus,whencerebrospinalfluid(CSF)outflow fromtheventriclesisblockedandCSFisforcedintotheinterstitiumofthebrainbythehighpressurein theventricularsystem.
Osmoticedemaisduetodecreasedplasmaosmolarity(forexample,inthesettingofthesyndromeof inappropriateADHsecretion[SIADH]orwithrapidglucosereductioninpatientswithhyperosmolar hyperglycemicstate).Undernormalcircumstances,theosmolarityoftheCSFandextracellularcerebral
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fluidislessthanthatofplasma.Ifplasmaosmolarityfalls,fluidshiftsintothebrain.
Whydoescerebraledemamatter?Becausetheskullisafixedspaceandanyincreaseinthevolumeof itscontentscanresultinelevatedintracranialpressure,whichbringsustoournexttopic.
ElevatedIntracranialPressure
Physiology
Intracranialpressure(ICP)isthepressurewithinthecraniumoftheskull.1Intheeighteenthcentury,two ScottishsurgeonsnamedAlexanderMonroandGeorgeKelliecameupwithahypothesisthatstill remainstheclearestwaytothinkaboutICP.TheMonro-Kelliedoctrine,asitisnowknown,statesthat intracranialvolumeismadeupofthreecomponents—blood,CSF,andbraintissue—andthatthisvolume mustremainconstant.Anyincreaseinonecomponentshouldthereforeleadtoadecreaseinoneorbothof theothertwo.
Let’stakeanexampleofagrowingbraintumor.Asthetumorgrows,thetissuecomponentof intracranialvolumeexpandsand,becausetheskullispoorlycompliant,eventhissmallincreasein volumeleadstoarelativelylargeincreaseinpressure.Thisincreaseinpressure,however,willbe quicklybufferedbydisplacementofothercompartments.Ingeneral,thevolumeofCSFdecreasesfirstto compensate.Intime,ifthetumorcontinuestoexpand,bloodvolumewillalsodecrease(resultingin ischemia)and,ultimately,braintissueitselfwillbedisplaced,forcedtoherniateoutsideoftheskull.
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Intracranialvolumeismadeupofthreecomponents:CSF,braintissue,andblood(A).Inthesettingofa growingmasslesion,CSFtendstodecreasefirst(B),followedbybloodvolume(C)andultimatelybrain tissue(D).
HereisonemorewaytothinkaboutICP.Aswe’vejustdiscussed,pressurechangeswithintheskull canaffectbloodflow.Inordertoadequatelyperfusethebrain,bloodmustbepumpedagainstapressure gradient.Ifyou’veeverinflatedabasketball,you’veexperiencedthisfirsthand.Atthestart,theballis compliant—notatallliketheskull—butasitinflates,thewallsbecomestiffandthepressureinsiderises. Thehigherthepressurerises,theharderitbecomestopumpairintotheball.Thesameeffortthat,inthe beginning,easilypumpedairinsidetheballbecomeslessandlesseffectiveuntilitfails:itnolonger overcomesthepressureinsidetheball,andairentryceases.Thephysiologicprocessthatenablesbrain perfusionismuchthesame.Theheartandarteriesgenerateabloodpressurethatforcesbloodintothe bloodvesselswithintheskull.Thedifferencebetweenthispressure(themeanarterialpressure,MAP) andthepressureinsidetheskull(theICP)iscalledthecerebralperfusionpressure(CPP)andisdefined asthenetpressuregradientthatcausesbloodtoflowtothebrain.
CPP=MAP−ICP
WhentheICPgoesup,theCPPgoesdown,resultinginalackofbloodflowtothebrainandsubsequent ischemia.
Box14.1CerebralAutoregulation
https://t.me/med1917
Howdowemaintainstablecerebralbloodflow(CBF)andcerebralperfusionpressure (CPP)inthefaceofdrasticfluctuationsinsystemicbloodpressure?Whydowenotalways immediatelypassoutorevenhaveastrokewhenoursystemicbloodpressurefalls? Conversely,whydowenotimmediatelybleedintoourbrainwhenoursystemicblood pressurerises?
Cerebralautoregulationistheprocessbywhichvasoconstrictionandvasodilationmaintain stableCBFoverarangeofCPPs.AsbloodpressurerisesandCPPincreases,intracranial vesselsvasoconstrict,increasingresistanceandtherebymaintainingstableCBFand, consequently,ICP.WhenbloodpressurefallsandCPPdeclines,intracranialvessels vasodilate,decreasingresistancetoallowthelowerCPPtomaintainastableCBFand adequateperfusiontothebrain.Theprecisepathophysiologyallowingforappropriate vasodilationandvasoconstrictionisunclear(thereappeartobemetabolic,autonomic,and myogenicfactorsinvolved),buttheprocessisaneffectiveone:mostpeopleareableto maintainastableCBFoverarangeofapproximately50to150mmHgofCPP.Whenthe limitsofautoregulationareexceeded,bloodvesselswilleithercollapse(frombeing underfilled)orbeforciblydilated(fromexcesspressure).Ischemiaandhemorrhage, respectively,canresult.
Bymeansofvasoconstrictionandvasodilation,cerebralautoregulationallowsforastable CBFoverarangeofapproximately50to150mmHgofCPP.
CausesandPresentationofElevatedICP
https://t.me/med1917
CommoncausesofincreasedICPinclude:
Masslesions(braintumors,intracranialabscesses,hematomas) Cerebraledema(frommassiveischemicstroke,severetraumaticbraininjury,masslesions)Obstructionofvenousoutflow(venoussinusthrombosis)  Obstructive hydrocephalus (excess accumulationof CSF resulting from mechanical blockage of CSFflow,oftencausedbytumorsorothermasslesions)  Communicating hydrocephalus (excess accumulation of CSF in the absence of mechanical obstruction);therearetwomajorcauses:
Decreased CSF absorption (secondary to intracranial infection, which can clog up the arachnoid granulations with inflammatory exudateandtherebypreventCSFabsorption;subarachnoidhemorrhage,which candothesame withblood;and leptomeningealmetastasis,withtumorcells) IncreasedCSFproduction(secondarytoCSF-producingtumors,suchaschoroidplexuspapillomas)
ElevatedICPmostoftenpresentswithrelativelynonspecificsymptomssuchasheadache(thoughttobe theresultofpressureonthepainfibersofCN5thatrunintheduraandonbloodvessels),nausea, vomiting,anddepressedconsciousness(presumablyaresultofdistortionofthethalamicandbrainstem reticularactivatingsystem,whichmediatesarousalandattention).
Signsonexaminationcanincludepapilledema(swellingoftheopticnerveheadduetoelevatedICP) andaCN6palsy(duetopressureonthenerveattheskullbase).Thedevelopmentoftheso-called Cushingtriad—bradycardia,hypertension,andrespiratorydepression—canindicateimminent herniation.Seepage363foradiscussionofspecificherniationsyndromes.
(A)Papilledemaseenonfunduscopy.Notetheblurredmarginsoftheopticnervehead.(B)Anormal sharplydefinedopticdisc,forcomparison.(ModifiedfromFreddoTF,ChaumE.AnatomyoftheEyeand Orbit.WoltersKluwer;2017.)
ManagementofElevatedICP
PatientswhoareatriskofelevatedICP—thosewithanacutelybleedingtumor,forinstance,orwitha
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