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

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Rigidityisonemanifestationofwhatistermedhypertonia.Abnormalmuscletonecanbe describedaslow(hypotonic)orhigh(hypertonic).Hypertoniacanfurtherbedividedinto rigidityandspasticity.Rigidityisvelocityindependent—inotherwords,theresistanceto passivemovementdoesnotchangewithmovementofthelimb—andisusuallydueto extrapyramidaldisease,suchasisseenwithPD.Spasticityisvelocitydependent— resistanceincreasesasthelimbisaccelerated—andismostoftenduetopyramidaldisease. Patientswithpriorstrokesinvolvingthecorticospinaltracts(forexample,alacunarstroke involvingthecoronaradiata)oftendevelopspasticityintheaffectedlimb(s).Tobeclear, though,don’tbeconfusedbytheseeminglycontradictoryprefixes:althoughtherigidity associatedwithPDisaformofhypertonia,PDitselfisahypokineticmovementdisorder, thatis,characterizedbythelossofmovement.
Cogwheelrigidityatthewrist.
Bradykinesiameansslownessofmovement,butpatientsoftendescribethisasfeelingsluggishortired. Youmaynoticebradykinesiawhenyouaskyourpatienttoperformatasksuchaswritingorbuttoninga shirt,orwhenyourpatiententersyourofficetakingshort,shufflingsteps(armswingcanalsobe decreasedorevenabsent).Othergaitabnormalitiesmayincludefreezing(asudden,temporaryinability tomove)andfestination(atendencytoinvoluntarilyspeedup).
The“maskedfacies”ofPDisanotherexampleofbradykinesia:spontaneousfacialmovementsare
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decreased,makingthepatientappearlessemotive.Decreasedblinkrategivesthepatienttheappearance ofstaring.Thevolumeofthepatient’svoiceisalsooftendiminished(referredtoashypophonia). Bradyphrenia,ormentalslowness,isalsoacommoncomplaint.
ThemaskedfaciesofParkinsondisease.
Posturalinstabilitymanifestsitselfasdifficultywithbalance.The“pulltest”measurespatients’ abilitytomaintainanuprightposturewhenyoupullbackwardontheirshoulders(bepreparedtocatch yourpatientiftheyareunabletorespondtoretropulsionandfallbackward).
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PerformingthepulltestinPD.
Otherclinicalsymptomsandsignscanemergeasthediseaseprogresses.Neuropsychiatricdifficulties rangefromissueswithimpulsecontrol(oftenworsenedbydopamineagonisttherapyusedtotreatPD;see page339),anxiety,anddepressiontofrankpsychosiswithhallucinations,memoryloss,anddementia.If prominentfeaturesofpsychosisanddementiaappearearlyon,dementiawithLewybodies(seepage193) andnotPDisthemorelikelydiagnosis.Autonomicsymptoms,includingincontinence,orthostatic hypotension,sexualdysfunction,andconstipationarealsocommon.Insomniacanbeaccompaniedbyor betheresultofanyofseveralsleepdisorders,notablyrestlesslegsyndrome,periodiclimbmovementsof sleep,andespeciallyrapideyemovement(REM)sleepbehaviordisorder(seepage351).
Box13.4PremotorSymptomsofPD
CommonpremotorsymptomsofPD(symptomsappearingbeforethemotormanifestations ofthedisease)includeREMsleepbehaviordisorder(seepage351),anosmia(lackof smell),constipation,anddepression.IfyoususpectPDinapatientwhomaynotclearlybe exhibitingsomeoralloftheclassicmanifestationsofthedisease,thesearegoodthingsto askabouttohelpguideyouintherightdirection.
Diagnosis
PDisaclinicaldiagnosis.Formaldiagnosticcriteriaincludebradykinesiaplusatleastoneother clinicalfeatureofPD.Routineneuroimagingisnotnecessaryformostpatientsunlessyouareconcerned
aboutapossiblesecondarycauseofparkinsonism(seepage344).Afavorableresponsetoalevodopa challengewillclinchthediagnosisofPDandcanofteneffectivelyruleouttheatypicalparkinsonisms (seepage342).
Box13.5AdvancedImagingforPD
Toreiterate,PDisaclinicaldiagnosis.MRIisnotnecessaryinpatientswithclassic symptomsandagoodresponsetolevodopa,butitmaybeusefultoexcludesecondary causes(seepage344)inpatientswithatypicalpresentationsofthedisease.More advancedMRItechniques,suchasMRspectroscopyanddiffusiontensorimaging,mayoffer highersensitivityfordetectingPD-relatedneurodegeneration,buttheirefficacyand diagnosticutilityremainunknown.DaTscan,aspecifictypeofsingle-photonemission computedtomography(SPECT)scan,enablesvisualizationofdopaminetransporterlevelsin thebrainandcanhelpdistinguishpatientswithPDoratypicalPDsyndromesfrompatients withotherdiseasessuchasessentialtremor.Thesescanscannot,however,distinguish betweenPDandatypicalPDsyndromes.Thusfar,evidencesuggeststhatthediagnostic accuracyofDaTscansisinmostcasesnobetterthanthatofagoodclinicalhistoryand examination.
Treatment
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BecausethelossofdopaminergicneuronsisresponsibleformostofthesymptomsofPD,itisnot surprisingthatlevodopa,themetabolicprecursorofdopamine,isthemaintherapeuticagent.Whynot dopamineitself?Because,unlikelevodopa,dopaminedoesnotcrosstheblood-brainbarrier.However, levodopacanbeconvertedintodopamineintheperiphery,limitingitsavailabilitytothebrainand causingnausea,vomiting,andorthostatichypotension.Itisthereforecombinedwithcarbidopa,adopa decarboxylaseinhibitorthatpreventstheperipheralconversionoflevodopaintodopamine.The combinationofthesetwoagentshasbeenthebasisoftherapyforPDformanyyears.
Patientstypicallydowellonlevodopaforseveralyears,butafteratimethebeneficialeffectswear off.Patientstendtorequirehigherandhigherdosesofmedicationandmaybegintoexperiencesudden “on-off”fluctuationsintheirsymptoms.Theoffperiodscanbesevere,resultingindisablingimmobility. Medication-induceddyskinesias—involuntarymusclemovements—aswellassleepdisorders, psychiatricdisorders,troublewithspeechandswallowing,anddementiacanalsoemerge.
Pharmacologictherapyshouldbeinitiatedassoonassymptomsbecomedisablingoradverselyaffect thepatient’squalityoflife.Levodopa-carbidopaisthemosteffectivemedicationandisfirst-line therapy.Otheragentscanbeaddedasadjunctivetreatmentforpatientswhoarenolongeradequately respondingtolevodopa-carbidopaalone:
Dopamineagonists(pramipexole,ropinirole, or bromocriptine).Thesecancausesedation,lower extremityedema,andimpulsecontrolissues. MAO-Binhibitors(selegiline,safinamide,orrasagiline).Insomniaisacommonsideeffect.COMTinhibitors(entacaponeortolcapone).COMT(Catechol-O-methyltransferase)isanenzyme thatbreaksdownboth dopamineandlevodopa.COMTinhibitorstherefore prolongthehalf-lifeof levodopa. Theycan causegastrointestinalside effects,sleepiness,andurinediscoloration(todark yellowororange;thisisbenignbutcanbeupsettingifpatientsarenotwarnedbeforehand!).Liver functiontestsmustbemonitoredinpatientsontolcapone. Anticholinergics (trihexyphenidyl, benztropine). These are usedpredominantlyto treat tremorand drooling.Typicalanticholinergicsideeffects(dryeyes, drymouth,constipation, urinaryretention, etc.)arecommon. Istradefylline. This adenosine A2a receptor antagonist probably acts by increasing dopaminergic
activity andisapprovedonlyforuseasanadjuncttolevodopa-carbidopatherapyinpatientswith frequentorsevere“off”periods. Amantadine.ItsmechanismofactioninPDisunknown,althoughithasbeenpostulatedtohaveboth indirectanddirectdopaminergiceffects.Amantadine canbeusedasmonotherapyinpatientswith verymilddisease.Itcanalsobeusedasanadjunctivetreatmenttohelpreducelevodopa-associated dyskinesias.Sideeffectsareuncommonbutcanincludeankleedemaandlace-likeskindiscoloration referredtoaslivedoreticularis.
Box13.6MAO-BandCOMTInhibitors
TheMAO-BinhibitorsandCOMTinhibitorsworkbyblockingthemetabolismofdopamine. Thesedrugsarelesspotentthanlevodopa,buttheycanbedosedlessfrequentlyandare lesslikelytocausedyskinesias.Mostoften,thesedrugsareaddedtolevodopatherapyto reducemotorfluctuationsinadvanceddiseaseandtoallowtheuseoflowerdosesof levodopa.
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Box13.7Non-PharmacologicTherapies
Encouragingphysicalactivityisanimportantcomponentofimprovingthequalityoflifeof patientswithPD.Thereisgoodevidencethatstartingexerciseearly,includingbalanceand gaittraining,resistanceandstrengthexercises,andaerobicexercise,canhelppatients maintainandoftenimprovetheirmotorfunction.Physicaltherapy,occupationaltherapy,and speechtherapycanalsobeusefulwhenindicated.Nocomplementaryoralternative therapieshaveyetbeenfoundtobebeneficial.Noparticulardietaryinterventionsare currentlyrecommended,althoughongoingstudiesareevaluatingpossiblelinksbetween alteredintestinalmicrobiotaandPD.
Nopharmacologictreatmenthasyetbeenshowntoalterthenaturalhistoryofthedisease.
Neurosurgicaltherapyisavailableforpatientswithadvanceddisease.Themostcommontechnique usedisdeepbrainstimulation(DBS),inwhichelectrodesareimplantedinthebrain(typicallyintothe substantianigraorglobuspallidus)wheretheydeliverhigh-frequencyelectricalstimulation.DBShas beenapprovedforpatientswhohavehadthediseasefor4yearsormoreandareexperiencingmotor fluctuations.MostpatientsundergoingDBSexperiencesignificantlyimprovedmotorfunctionanda lesseningofdyskinesia,butothersymptoms,includingposturalinstability,cognitivefunction,speech disorders,andgaitfreezing,maynotimproveandcansometimesworsen.
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DeepbrainstimulationforPD.Becausetheneuronsofthebraindonotsensepain,theelectrodecanbe leftinplacewithoutcausinganydiscomforttothepatient.
Prognosis
Despitemaximaltherapy,mostpatientswillultimatelydevelopdisablingcomplications.Dementiais common,affectingasignificantminorityofpatientswithin5years.By10years,about25%ofpatients willrequirenursingassistance,andaveragelifeexpectancyfromthetimeofdiagnosisislessthan 10years.
DifferentialDiagnosis:DisordersThatCanMimicParkinson Disease
Manydifferentdisorders,bothphysiologicandpathologic,canmimicPD.Let’stakeafewminutestogo throughthevarioustypesoftremors,aswellastheatypicalparkinsoniansyndromesandsecondary causesofparkinsonismthatarecommonlymistakenforprimaryoridiopathicPD.
Tremor
Parkinsondiseaseisonlyonecauseoftremorandnotthemostcommonone.Therearemanydifferent
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typesandcausesoftremor,butwecansortthemintojustafewessentialvarieties.
Parkinsondisease.Aswealreadydiscussed,thetremorofParkinsondiseaseisusuallyaresting tremor.Ittendstostartunilaterallyinonehand,butitcanalsoaffectthelegs,thechin,orthetorso. TremormaypersistforyearsbeforeothersymptomsorsignsofParkinsondiseasedevelop.
EssentialTremor.Essentialtremor(ET)isthemostcommonofallmovementdisorders.Itisprimarily anactiontremorthatiskinetic(broughtoutbyvoluntarygoal-directedmovementsuchasdrinkingacup ofcoffee)and/orpositional(sustainingananti-gravityposturesuchasholdingthearmsoutstretched).ET isusuallybilateral,althoughoftenasymmetric,andcanaffectthelimbsaswellasthevoice,theneck,and thehead.Itoftenimproveswithalcoholandisworsenedbystressandanxiety.Unlikephysiologictremor, itisnottypicallyworsenedbycaffeine.Abouthalfofcasesarefamilial(ETisautosomaldominant),and mostbegininadolescenceoryoungadulthood,althoughonsetlaterinlifecanoccur.Ittendstogetworse overtime.Althoughtraditionallyconsideredabenigncondition,itcanbecomequitedisabling. Propranolol(abetablocker)andprimidone(ananticonvulsant)arethefirst-linedrugswhenmedication isrequired,buttheyaretypicallyonlyeffectiveformildcases.Botoxisemergingasapotential alternativeoption.
EnhancedPhysiologicTremor.Weallhavethistypeoftremortosomeextent—itisnotpathologic—but insomepeopleitcanbecomedisabling.Itisanactiontremorthatcanbepositionalorkinetic.Itis exacerbatedbystress,caffeine,andvariousmedications,includingbeta-agonists,amphetamines, valproate,lithium,tricyclicantidepressants,selectiveserotoninreuptakeinhibitors,andsteroids.
Box13.8
Forthoseofyouwithagoodsenseoftiming,youmaybeabletodiscernthatthetremorof ETisfasterthanthetremorofPD,typically8to10Hz(i.e.,8to10cyclespersecond) comparedwithonly3to7Hz.
FunctionalTremor.Thistypeoftremorisareactiontostressortraumaortheresultofanunderlying mooddisorder.Unliketheothertypesoftremor,itsonsetisoftensuddenandsevere.Ittendstoimproveif thepatientisdistracted.Onecommoncharacteristicoffunctionaltremorisentrainment:ifyouhaveyour patienttapoutarapidrhythmwiththeunaffectedhand,thetremorintheaffectedhandwillchangein frequencytomatchthatofthetappinghand.
OtherCausesofTremor.Alwaysconsiderthepossibilityofhyperthyroidism(checkathyroid stimulatinghormonelevel!),uremia,andalcoholism(overuseorwithdrawal).Otherdisorderscancause tremor,buttheyarefarlesscommon.Oneyoudon’twanttomissisWilsondisease,adisorderofcopper metabolism(seepage344).
Thesedifferenttypesoftremorcanusuallybesortedoutbythenatureofthetremorandtheclinical contextinwhichtheyoccur.Misdiagnosis,however,iscommon;patientswithearlyPDareofteninitially thoughttohaveessentialtremor.
TypeofTremor Description Example Resting Occurswiththerelevantbodypartsupportedagainstgravity Parkinsondisease Action Essentialtremor
Positionalorpostural Occurswhentryingtoholdapositionagainstgravity Kinetic Occurswithvoluntary,goal-directedmovement
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Functional Canbeanything,typicallyofsuddenonset Duetostress,trauma,mooddisorder
ThedifferentialdiagnosisofPDcanbemorechallengingwhenfeaturesotherthantremordominatethe clinicalpicture.InsomepatientswithPD,tremormaybeminimalorevenabsent.Youthenneedto consideragroupofdisordersknowncollectivelyastheatypicalparkinsoniansyndromes,orparkinson­plussyndromes.
TheAtypicalParkinsonianSyndromes
AllofthesedisordersarefarlesscommonthanPD.Onekeytosuspectingtheseconditions,alongwith thepresenceofparkinsonianfeaturesandtheabsenceofapredominantrestingtremor,istheirfailure, unlikePD,torespondtotherapywithlevodopa.Thereisalotofclinicaloverlapamongthesesyndromes, buteachhassomedistinguishingfeaturesworthhighlighting.Themajortypesofatypicalparkinsonian syndromesare:
Progressivesupranuclearpalsy Corticobasaldegeneration DementiawithLewybodies Multiplesystematrophy
ProgressiveSupranuclearPalsy.Thisdisorderisthemostcommonoftheatypicalparkinsonisms. Rigidityisoftenprominent,andittendstoimpacttheaxialmusculaturemorethantheextremities, resultinginearlyposturalinstabilityandfrequentfalls.Supranucleargazepalsyisalsocharacteristic: patientsareunabletolookupordownwhenaskedtodoso,butupgazeoccursinvoluntarilywhenthe neckisflexedanddowngazeoccurswhentheneckisextended.Arestingtremorisusuallyabsent. Magneticresonanceimaging(MRI)classicallyshowsprominentmidbrainatrophyresultinginwhat’s knownasthe“hummingbirdsign.”
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Thehummingbirdsign,seeninprogressivesupranuclearpalsy.Themarkedlyatrophicmidbrain representstheheadandtheponsrepresentsthebody.(A,reprintedfromGraberJJ,StaudingerR. TeachingNeuroImages:“Penguin”or“hummingbird”signandmidbrainatrophyinprogressive supranuclearpalsy.Neurology.2009;72:e81.)
CorticobasalDegeneration.Tremorisnotprominent,andpatientspresentinsteadwithpredominantly asymmetricrigidityandbradykinesia.Dystoniacanleadtopainfulcontractures.Corticalsigns,including aphasia,corticalsensoryloss(suchasagraphesthesiaandastereognosis;seepage62),alienlimb phenomenon,anddementia,areoftenprominentandcanhelpdistinguishcorticobasaldegenerationfrom theotheratypicalparkinsoniansyndromes.Corticobasaldegenerationisrare,affectingonlyabout5per 100,000people.
DementiaWithLewyBodies.WediscussedthisdisorderindetailinChapter7.Briefly,thediagnosis requiresacombinationofdementiawithatleastoneofthekeyfeaturesofPD.Cognitivefluctuationsand visualhallucinationsareclassicfeatures.
MultipleSystemAtrophy.Thisdisordershouldbesuspectedinpatientsofmiddleagewhodevelop featuresofparkinsonism(again,patientsdeveloprigidityandbradykinesiabutnotarestingtremor)plus earlyprominentautonomicdysfunctionand/orcerebellarinvolvement.Autonomicmanifestationsinclude orthostatichypotensionandurinaryretentionorincontinence.Themostcommoncerebellarsymptomis ataxia.
SummaryoftheAtypicalParkinsonianSyndromes.Ifyouremembernothingelse,rememberthatallof theatypicalparkinsoniansyndromespresentwithsomeoftheclassicfeaturesofparkinsonismbut(1) tremorisnotprominentand(2)responsetolevodopaispoor.
Disorder ClinicalCharacteristics Pathology
Progressivesupranuclearpalsy Earlyposturalinstabilityandfrequentfalls,supranucleargazepalsy Tauopathy Corticobasaldegeneration Asymmetricdystonia,alienlimb,corticalsensoryloss Tauopathy DementiawithLewybodies Dementiaisearlyandprominent Alphasynucleinopathy Multiplesystematrophy Earlyautonomicdysfunctionand/orcerebellarinvolvement(ataxia) Alphasynucleinopathy
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