The Bizarre Disorder of Hemineglect - Brainline.org

Hemineglect is an unawareness or unresponsiveness to objects, people, and other stimuli—sometimes patients even ignore or disown their own left ... 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JenniOgden,PhD,PsychologyTodayBlogRelatedContent: VisionIsOurDominantSenseIntroductiontoVisionandBrainInjuryVisionIssuesAfterBrainInjuryHemianopsiaandDriving:AreWeAskingtheRightQuestions?HomonymousHemianopsia:RightVersusLeftHemisphericInjuryHemispatialInattention(VisualNeglect)ScanningTraininginNeurologicalVisionLossVisionandRehabilitationAfterBrainTrauma(Part1)VisionandRehabilitationAfterBrainTrauma(Part2)VisionandRehabilitationAfterBrainTrauma(Part3)Morethan100yearsafteritwasfirstdescribed,hemineglect—alsoknownasunilateralspatialneglect,orunilateralinattention—isstilloneofthemostfascinatingandmysteriousoftheneuropsychologicaldisorders.IhaveassessedmanypatientswiththisstrangedisorderandIamstillamazedbytheirbehaviors.Althoughwenowknowthathemineglectcanoccurinmanyformsandastheresultofdamagetovariousbrainareas,byfarthemostcommontypeisleftvisualhemineglect,anditoccursfollowingdamagetotherightparietallobeofthebrain.IntheworstcaseIsaw,thepatientsatinherwheelchairwithherheadscrewedaroundasfartotherightaspossible,andrefusedtolookorspeaktomeifIstoodonherleftside.Shewouldeatonlythefoodofftherightsideofherplate,andsherefusedtoacknowledgethatherleftarmandlegbelongedtoher.Attheotherendoftheseverityspectrum,visualhemineglectcanonlybepickedupbyaskingthepatienttodraworcopyapicture.Theywilleitherdrawonlytherightsideofthepicture,or,iftheydrawtheleftsidewillscribblethatsideveryroughly,ormissdetails.Theillustrationshereshowafacedrawnbyapatientwithmoderatehemineglect,andbelow,acopyofascene,whereonlythetreeandthehouseontherightsideofthescenearedrawn,andeventhehouseismissingbitsofitsleftside.Thisscenetesthasbroughtforthsomeveryamusingcommentsfrommypatients.Aftertheycompletetheircopy,Ipointtothefenceinthemodeldrawing(atthetopoftheillustration)andaskthemwhatitis.Oncetheirattentionisdrawntoit,theyusuallyanswercorrectly."It'safence,ofcourse,"theysay,lookingatmeasifI'vetakenleaveofmysenses."Wellwhydidn'tyoudrawitinyourcopy?"Iask.Ihavefieldedarangeofanswerstothisquestion,butthis,fromawomanwithalargebraintumourinherrightparietallobe,ismyfavorite."IsupposeIcouldifyoureallywantmeto,butitissuretoblowdowninthenextwind!"Shethendrewaveryroughlookingfence.WhenIaskedhertodrawthetreeontheleftofthemodel,sheinformedmethatshecouldn'tdrawtrees,andIcouldnotinducehertodrawit.Hemineglectisanunawarenessorunresponsivenesstoobjects,people,andotherstimuli—sometimespatientsevenignoreordisowntheirownleftlimbs—intheleftsideofspace.Itisnotthatthepatientcan'tseethestimuli,butratherthattheyhavelostthewillormotivationtoattendtothemorrespondtothem.Andwhatismeantbythe"leftsideofspace"?Imaginelookingatapicture,andmentallydividingitdownthemiddle.Thepartofthepicturetoyourleftistheleftsideofspacewhenyouareaskedtocopythatpicture.Nowimagineyouaresittinginaparkwithaplaygroundonyourrightsideandaduckpondonyourleftside.Theduckpondfallsinyourleftspace,andifyouhadarightparietalstrokeandhemineglectyoumightonlytakenoticeoftheplayground.ButnowimaginethatIaskyoutoturnyourheadandlookattheduckpond.Nowwhatyounoticeistherightsideofthepondwithreedsalongthebank,butyouneglecttheducksthataregatheredontheleftbankofthepond."Doyouseetheduckpond?"Iask."Iseethepond,butitisn'taduckpond.Therearen'tanyducks!"youmightanswer.Evenwhenrefusingtonoticethingsontheleftresultsinpainordiscomfort,thepatientstillneglectsthem.Thus,whentheyarewheelingthemselvesalongintheirwheelchairtheywillconstantlybangintotheleftwall,bruisingtheirlegagainandagain.But,sometimes,inextremesituations,theywilltakenoticeofwhatisintheirleftspace.Inoneinterestingexample,thefamilyofamanwithhemineglectgotakitten.Althoughherarelyrespondedtoanythingoranybodyonhisleft,ifthekittenwasplayingbytheleftwheelofhiswheelchair,themanneverbangedintoit.Mindyou,whenaskedwhatwasonthefloor,heneverremarkedonthekitten!Patientswithhemineglectoftenhavesomedegreeofparalysisoftheirleftlimbs,asthedamagetotheirrightparietallobealsoencroachesonthemotorstripintheposteriorpartofthefrontallobe,andthiscausesthelimbweakness.Butithasbeenshowntimeandagainthatthislimbweaknessisnotthecauseofthehemineglect.Manypeoplewithparalysedlimbsareperfectlyabletoattendtobothsidesofspace,butthosewhoalsohavehemineglectoftenappeartohaveamuchgreaterlimbweaknessthantheyare"entitled"to.Forexample,eveniftheirarmisonlyalittleweak,whenaskedtoraiseittheywillactasifthearmisheavyandstiff.Yetsometimestheywillspontaneouslyusetheleftarmnormallyiftheyarenotthinkingaboutit;forexampleiftheyareusingtheirrighthandtoeat,andaflycrawlsontotheirface,theirlefthandmayriseupandshootheflyaway!Italmostseemsasifpatientswithhemineglectarepurposefullytryingtobedifficult.Thisisnotthecase,ofcourse:hemineglectonlyhappensafterspecificareasofthebrainaredamaged.Andthatiswherethemysterylies.Researchershaveyettocomeupwithacompletelysatisfactorytheoryaboutwhythebrainactslikethis.Themostpopulartheoryisthattherighthemisphereofthebrain,andespeciallytheparietallobe,specializesinattendingtothespaceonbothsides,whereastheleftparietallobe(perhapsbecauseofitsheavyinvolvementinlanguagecomprehension)onlyattendstotherightsideofspace.Thus,whentherightparietallobeisdamaged,itcannolongerattendtotheleftorrightofspace,buttheintactleftparietallobeisabletoattendtotheright.Althoughtherearecasesofleftparietaldamagecausingrighthemineglect,thistheoryalsohelpsustounderstandwhythesecasesaremuchlesscommonandrarelyassevereascasesoflefthemineglect.Iftherightparietallobeisstillintactitcancompensateforthelossoftheleftparietallobe,asitcanattendtobothsidesofspace.Butthistheorydoesn'texplainwhythepatientmakesexcusesfortheirinattention.Perhaps,whenfacedwiththisbizarrelossofhalfofspace,ourlogicalhumanmindhastofindsomewaytoexplainittoourselves.Sowemakeupexcuses,almostasadefensemechanism,andcomeupwithstatementssuchas"Ican'tdrawtrees"or"thefencewillprobablyblowdowninthenextwind,sothereisnopointindrawingit."ReadotherblogsbyJenniOgden.PostedonBrainLineSeptember11,2012.OriginallypublishedinPsychologyToday,©JenniOgden2012.Usedwithpermission.www.psychologytoday.com.MoreinformationaboutJenniOgden. 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