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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
Thebasicreflexesandthenerverootsresponsibleforthem.
Box1.10ThePlantarandHoffmannReflexes
TheplantarandHoffmannreflexesareindicativeofuppermotorneurondamage.Theplantar reflex(commonlyreferredtoastheBabinskireflex,althoughthetermBabinskiactually referstoaphysicalsignthatispresentwhentheplantarreflexisextensorandabsentwhen it’sflexor)ispresentatbirthbutnormallyextinguishedbyabout1yearofage.Itiselicitedby strokingthesoleofthefoot(seepicture).Ifthereflexispresent,thebigtoewillmove upward(extensorresponse);ifnot,thetoeflexesdowntowardthe(flexorresponse).The Hoffmannreflexistheupperextremityequivalentandiselicitedbyflickingthetipofthe middlefingerdownward.Ifpresent,thethumbandindexfingeronthesamehandwillflex together.Inpersonsovertheageof1year,thepresenceofeitherofthesereflexesis abnormal.
TheBabinskisign.
Coordination
Coordinationtestsaretestsofcerebellarfunction.Therearemanyofthesetests;we’veselectedahandful oftheonesmostcommonlyused.Trythemall,becauseabnormalitiescanbeextremelysubtleandeasyto miss.
1.  Rapid alternatingmovements. Have yourpatientsresttheir hands ontheirlap, thenfliptheirpalms frombacktofrontrepeatedly. Difficultywiththistask,manifestedbytheinabilitytomaintainagoodrhythmoffront-back-front-back,iscalleddysdiadochok inesia.
2. Finger-nose-finger.Have yourpatients taketheir indexfinger,touchtheir noseandthentouchyour fingersuchthattheymustfully extendtheirarminfrontofthem.Dothisrepeatedly,movingyourfingersothattheyareconstantlyreachingforanewtarget.Difficulty withthistask—iftheirfingerzigzagsbackandforth,isunabletoreliablylandpreciselyonyourfingertiporontheirnose,orconsistently
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pointspastyourfingertip—iscalleddysmetria.
3. Heel-to-shin.Haveyour patientsplacetheir leftheel ontheirrightknee,thendragtheir leftlegstraightdownandthenbackuptheir right leg repeatedly, staying directly on top of their tibia. They should be able to do this smoothly. Any incoordination (typically manifestedbyazigzaggingmotionsimilartowhatcanbeseenwithfinger-nose-fingertesting)canbeindicativeofacerebellarlesion.
Gait
Thegaitexaminationisperhapsthehardestpartoftheexaminationtointerpret.
Abnormalitiesingaitandbalancecanbeduetoalmostanything,withbothneurologic(motor,sensory, vestibular,cerebellar)andnon-neurologic(orthostasis,deconditioning)causes.Thatsaid,gaitis incrediblyimportanttoobservebecausetheabilitytowalkmatters.Let’ssayyou’redecidingwhetheror nottogivethrombolytictherapytoastrokepatientwho,inthestretcher,seemstohavemildleftleg weakness.Ifthepatientcanwalknormallydespitethis,therisksoftherapymayoutweighthebenefits.But iftheytrytowalkandcannot,itislikelythatthispatientwillwantyoutodoeverythinginyourpowerto makethembetter.
Wheneveryou’reabletodoso,testregularwalking,toe-andheel-walking,andtandemgait(withone footplaceddirectlyinfrontoftheother,heel-to-toe).
Acoupleofspecificgaitdisorderstoknow:
1. Ataxicgait.Mostoftenduetocerebellarpathology,ataxicgaitischaracterizedbyawide-basedstanceandstaggering,unsteady,and uncoordinatedmovements.Thesepatientscansometimesbemistakenforbeinginebriated.
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2. Shufflinggait.Classic forParkinsondisease,thistypeofgaitcanalsobeseenin normalpressurehydrocephalus.Itischaracterized bysmallshortstepswithverylittlefootelevationofftheground.
So,thiswascertainlyalotofinformation,andyou’reprobablythinkingthatperforminga comprehensiveneurologicexaminationwilltakeatleastaweek!Inreality,theentireexaminationoften takesonlyseveralminutes.Asyougetmoreexperienced,youcanpickandchoosefromthevarious domains;forinstance,youlikelydon’tneedtotesteveryaspectofmentalstatusinahealthy25-year-old presentingwitha10-yearhistoryofmigraine.However,especiallyatthebeginning,it’simportanttogoin orderthrougheachcomponentoftheexaminationsothatyoudon’tmissanythingalongtheway.
NoteTemplate:AnExampleofHowYouMightDocumentaNormal NeurologicExamination
Ifyou’rewonderinghowalloftheinformationinaneurologicexaminationisdocumented,checkoutthis exampleofanormalneurologicevaluation:
MentalStatus.Alertandorientedtoperson,place,andtime(AOx3),attentionintact,speechfluent, namingintacttohighandlowfrequencyobjects,repetitionintact,abletofollowsimpleandcomplex commandsacrossthemidline,recognitionandrecallintact.
CranialNerves.Discssharpbilaterally,visualfieldsfull(VFF)tofingercounting,pupilsequallyround andreactivetolightandaccommodation(PERRLA),extraocularmusclesintact(EOMI)without nystagmus,facialsensationintacttolighttouch(V1-3intacttoLT),facesymmetricwithequalactivation, hearinggrosslyintact,tongue/uvula/palatemidline(t/u/pmidline),sternocleidomastoid(SCM)and shouldershrugsymmetric.
Motor.Normalbulkandtone,5/5throughout,nopronatordrift(PND).
Sensory.Sensationintacttolighttouch(LT),temperature,pinprick(PP),vibrationandjointposition
sense(JPS),noextinctiontodoublesimultaneousstimulation(DSS;seeBox1.11),Rombergnegative.
Reflexes.2+andsymmetric,toesdown.
Coordination.Finger-nose-finger(FNF),rapidalternatingmovements(RAM),andheel-to-shin(HTS)
intact.
Gait.Steadynarrow-basedgait,abletoheel/toe/tandemwithoutdifficulty.
Notsobad,right?Thehardestpartcanbesortingthroughalloftheabbreviationsscribbledbybusy students,residents,andfellows;we’veincludedmanyofthemheresolateronyouwon’tfeellikeyou’re readingaforeignlanguage.
Box1.11HemineglectandExtinctiontoDoubleSimultaneous Stimulation
Hemineglectisaneurologicconditioninwhichpatientsloseawarenessofonesideofspace. Hemineglectcanbedramatic,suchaswhenpatientsfailtorecognizetheirownarmoronly appropriatelydresshalfoftheirbody,ormoresubtle,suchaswhenpatientsextinguishto doublesimultaneousstimuli.Extinction,intheworldofneurology,isdefinedastheimpaired abilitytoperceivetwostimuliofthesametypesimultaneously,anditindicatesarelatively
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subtleformofneglect.
Here’sanexample:let’ssayapatienthasdevelopedmildleft-sidednumbnessandneglect fromaright-sidedstroke.Ifyoutouchthepatient’slefthand,withhisorhereyesclosed,the patientwillbeabletotellyouthatyou’retouchingthelefthand;itfeels“less”thanifyou touchtherighthand,butthepatientisabletoperceivethestimulus.If,however,youtouch bothhandsatonce(againwhilethepatient’seyesareclosed),thepatientwillconsistently “extinguish”thestimuliontheleftandtellyouthatyou’reonlytouchingtherighthand.The patienthasproventoyouthatheorshecanfeelthestimulusontheleft,butwith“double simultaneousstimuli,”reliablyneglectsthatsideofthebody.Extinctiontovisualstimulican betestedaswell.
Becausethereisnoastand-alonecategoryfor“neglect”withintheneurologicexamination,if youfindsensoryextinctiononexamination,youcandocumentitaspartofthesensory examination;visualextinctioncanbedocumentedundercranialnerves(rightnexttovisual fields);theinabilitytorecognizeone’sownarmcangoundermentalstatus.Howeveryou choosetodocumentneglect,theimportanttakeawayhereistoremembertotestforit.It’s oneexampleofhowimportanttheneurologicexaminationcanbe:youcandetectavery subtlebutseriousdeficitthat,almostbydefinition,thepatientisnotawareof.
IsitNeurologic?
Oneofthebiggestchallengesofneurologyishowtodistinguishneurologiccomplaintsanddiseasesfrom nonneurologicones.If,forexample,apatientpresentswithnew-onsetconfusion,whatwouldmakeyou thinkthattheprimaryproblemiswiththebrainandnot,say,withthekidneys(uremia)ortheliver (hepaticencephalopathy)?
Themosthonestansweristhatweoftendon’tknow.Thedistinctioncanbehard,andeventhemost experiencedneurologistswilltellyouthatyoushouldhavealowthresholdtoconsideranyandall neurologicpossibilities.Themoresatisfyingansweristhattherearefindings—reallyonlyahandfulof findings—thatwelookfortohelpguideus.Likeflashingstopsignsstucktothepatient’sforehead,these findingsshouldmakeusstopinourtracksandfeelconfidentthataprimaryneurologicdiagnosisislikely.
NumberOne:FocalityAfocalneurologicdeficitisasymptomthatcanbelocalizedtoaparticular anatomicsiteinthenervoussystem.Unilateralweaknessorsensorylossareclassicfocalsymptoms. Changesinspeech,language,vision,hearing,andcoordinationcanalsobefocalsymptoms.The remainderofthisbookwillhelpclarifythesesymptoms—howtheytypicallypresentandwhere, anatomically,theycomefrom(or,inneurologistspeak,“localizeto”).Focalneurologicsymptomsare usuallytheresultofneurologicdisease,butthereareexceptions.Forexample,severehypo-and hyperglycemiacancausefocalsymptomsaswell.
NumberTwo:GazePreferenceApatientwitharightgazepreferencewillprefertolooktotheright.If thegazepreferenceismild,thepatientmayoccasionallyvoluntarilylooktotheleft.Ifit’salittleworse, theywillonlylooktotheleftwhenadequatelystimulated(e.g.,ifyouwaveafamiliaritemoryelloutto thepatientfromtheirleftvisualfield).Ifit’ssevere,theymayneverlooktotheleft,nomatterhowloud youshoutfromtheirleftside.Whenyouseeagazepreference,youshouldhavelittledoubtthatthepatient hasanunderlyingneurologicproblem.
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Apatientwitharightgazepreference.
NumberThree:LackofanAlternateExplanationLet’sgobacktoourconfusedpatient.Whatifheis anend-stagerenalpatient,andwediscoverthathehasmissedhislastthreedialysissessions?Inall likelihood,thispatientisconfusedduetouremicencephalopathy,andhewillimprovewithtimeand dialysis.Thereisnourgentneedtoconsiderprimaryneurologicetiologiesunlesshefailstoimproveor —andthisiscritical—ifhealsohaseitherFOCALITYoraGAZEPREFERENCE.Butwhatifyour confusedpatientisnotmedicallyill?Whatifheorshehasbeencompletelyhealthyupuntiltoday? Withoutanobviousmedicaltriggertoexplaintheconfusion,wehavetothinkalittleharder.Oftenalot harder.Hereiswhereagoodneurologicexaminationandadditionalneurologictestingbecomeessential.
Box1.12Tip-Offstoa“Functional”NeurologicExamination
Somepatients,eitherconsciously(factitiousdisorders)orunconsciously(conversion disorders),feignneurologicdisorderswhentheydonothaveone.Theneurologicsymptom canbeanything:theymayclaimthattheycan’tseeoutofoneeyeorinsistthattheycannot movebothlegs.Theimportanceofidentifyingpatientswithfunctionalexaminationsisn’tto catchtheminalie,butrathertosparethemneedlessneurologictestingandaddressthereal issue,whichmaybeapsychiatricone.Therearespecifictestsforspecificcomplaints,buta coupleofbasicprincipleswillserveyouwell.Hereisonefromthesensorysideofthingsand onefromthemotorsidethatareoftenhelpful:
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Splitting the midline . Patients may complain that their sensation is abnormal or decreasedononesideoftheirface,and evaluationwill revealaprecisesplitdown the midline of their nose between the good side and the affected side. This is not physiologic.The cutaneousbranchesofthetrigeminal nerves are simply notwiredthat way; they overlap some to the contralateral side, so that organic neurologic deficits actuallycrossthemidline,usuallybyseveralcentimeters. Givewayweakness.Strengthtestingcanbebothpain-andeffort-limited,andpatients often require significant encouragement to demonstrate full strength. Occasionally, however,apatientwillinitially,briefly,offerfullresistanceandthensuddenlycollapse,or “give way” and provide no further effort. This is not characteristic of true motor weakness.
DiagnosticTools
Thediagnosticpossibilitiescanfeelendlesswhenyouareconfrontedwithapatientwithaneurologic disorder.Inmanycases,thehistoryandexaminationwilltellyouallyouneedtoknow,butnotalways. Thereareafew(justafew!)questionsyouneedtoaskyourselfafteryou’vetakenyourhistoryand completedyourexaminationinordertofigureoutyourimmediatenextstep:
1. Wouldthispatientbenefitfromimaging?
2. Wouldthispatientbenefitfromalumbarpuncture(LP)?
3. Wouldthispatientbenefitfromanelectroencephalogram(EEG)?
4. Wouldthispatientbenefitfromelectromyography(EMG)ornerveconductionstudies(NCS)?
Thesefourquestions,onceyourhistoryandexaminationhavebeencompleted,arepromptingyouto considertheremainingitemsinyourneurologictoolbox.Variousothertests,suchasserummarkersfor infection,inflammation,andimmunologicdisease,andurinestudiesfortoxicology,canbehelpfulas well,butthesefour—imaging,LP,EEG,andEMG/NCS—formthecruxofthediagnostictoolboxfor neurologicdisease.Theymaybeusedacutelyinurgentsettingstodeterminethebestandpotentiallylife­savingintervention,ormoreleisurelytoestablishthediagnosisinapatientwithacomplex,chronic presentation.
Butdon’tusethesetestshaphazardly,likethrowingdartsatadartboardandhopingtohitthecenter. Everytestcarriescertainrisks,notleastamongthemtheriskoffalsepositives(leadingtomore,often invasivetestingandahugeamountofanxietyforthepatient)andoverdiagnosis(uncoveringactuallesions butonesthatmayneverproveharmfultothepatient).Usethesetestswiselyandwell,andonlyin appropriatecircumstances.Whatarethosecircumstances?Well,that’swhyyouarereadingthisbook!
AQuickOverviewofHeadImaging
CTScan.CTscansarefastandrelativelyinexpensive.Theyexposethepatienttoionizingradiation,but aheadCTdeliversnomoreradiation(∼1.5mSv)thanaseriesofbackx-rays.Nevertheless,thisfactor shouldbetakenintoconsideration,particularlywhendecidingtoimagechildrenandpregnantwomen.
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CTscansdonotprovidethesamedegreeofanatomicdetailasMRIs,buttheycandetectstructural abnormalitiesandsignsofelevatedintracranialpressureandareactuallymoresensitivethanMRIfor identifyingacuteblood.
YoushouldexamineallCTscansfor:
1. Density.Acutebloodisbrightwhiteor“hyperdense,”whereasinfarctionfromanischemicstrokeisdarkeror“hypodense”compared withnormalbraintissue.Calciumdepositsalsoappearhyperdenseandareoftenseenwithinthechoroidplexusoftheventricles(these arenormal!).
2.  Gray-whitedifferentiation.Normal CT scans of the brain show clear delineationbetween the gray matter of the cortexand the subcorticalwhitematter.Blurringofthisdistinctioncanindicatestrokeorotheranoxicbraininjury.
3. Symmetry.Aswithallbrainimaging,symmetryiskey.Ifyouseesomethingononesideofthebrainthatyoudon’tseeontheother,it isinalllikelihoodabnormal.
4. Shift.Thefalxcerebri,thecrescent-shapedduralfoldthatseparatesthetwocerebralhemispheres,shouldbemidline.Ifit’sshiftedto oneside,pushed overbybloodoramass,youshouldbeimmediatelyconcernedabouttherisk ofherniation,thatis,brain tissuebeing forcedintoplacesthatitshouldn’tgo.
(A)AnormalCTscanofthehead.Youcanseechoroidcalcificationswithinthetemporalhornsofthe lateralventricles(acommon,physiologicfinding).(B)Adeepleft-sidedintraparenchymalbleed.(C)Alarge left-sidedposteriorcerebralartery(PCA)infarction.(A,reprintedfromHerzogE.Herzog’sCCUBook. WoltersKluwer;2017;B,reprintedfromKollefMH,IsakowW,BurksAC,DespotovicV.TheWashington ManualofCriticalCare.3rded.WoltersKluwer;2017;andC,reprintedfromCheng-ChingE,BaronEP, ChahineL,Rae-GrantA.ComprehensiveReviewinClinicalNeurology.2nded.WoltersKluwer;2016.)
MRI.MRIscansaremoreexpensiveandtakemoretimethanCTscans,buttheycanalsoprovide significantlymoreinformation.
Radiologistsusetheterm“intensity”asopposedto“density”todescribebrightnessonanMRI:things thatappearbrightarereferredtoas“hyperintense”(or“increasedsignal”),andthingsthatappeardark are“hypointense”(or“decreasedsignal”).
ThereareseveralbasicsequencesofMRIimaging(i.e.,differentwaysofmodifyingthemagneticfield, resultinginspecificimageappearances)thatyoushouldbefamiliarwith.Thesearelistedbelow.T1­weightedsequencesarethoughtofasthemostanatomical,bestatshowingthegrossanatomyofthebrain.
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T2-weightedsequencesshowcasepathology,becauseedemaandgliosis(scarring)appearbright.Fluid­attenuatedinversionrecovery(FLAIR)sequencesareT2-based,butwiththeCSFsignalsuppressed.This helpstohighlightabnormalincreasedsignalelsewhere.
T1 T2 T2FLAIR
CSF Dark Bright Dark Graymatter Dark Bright Bright Whitematter Bright Dark Dark
T1,T2,andFLAIRsequences.(ReprintedfromLouisED,MayerSA,RowlandLP.Merritt’sNeurology.13th ed.WoltersKluwer;2015.)
TwoadditionalimportantMRIsequencesyoushouldknowaresusceptibility-weightedimaging(SWI) anddiffusion-weightedimaging(DWI).
SWIisusedtodetectblood,whichappearsdark(calciumwillappeardark,aswell).Theprocessof determininghowlongthebloodhasbeenaround(i.e.,isitacuteorchronic)onMRIiscomplicated,and beyondthescopeofthisbook.Gradient-echo(GRE)sequencesaresimilartoSWIsequencesbutareless sensitivefordetectingblood.
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SWIsequenceshowingmultifocalcorticalhemorrhages(thelittleblackdots;seewhitearrows), consistentwithcerebralamyloidangiopathy(seepage79fordetails).(CourtesyofE.MarkHaacke,PhD.)
DWIisthefirstsequencetolookatwhenyouareconcernedaboutstroke.Itisusedtodetectcytotoxic edemaandinfarctedtissue,whichappearbrightwhite.Here,theterm“restricteddiffusion”isusedto
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