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NBME 23 Answers

nbme23/Block 1/Question#28 (51.9 difficulty score)
An otherwise healthy 82-year-old man is ...
Posterior cord syndromeπŸ”,πŸ“Ί
tags: neuro b12 vitamins 

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submitted by sajaqua1(557),
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orotriePs droc srmodeyn ucrsoc deu to atonrcniif fo the sretpioor afhl fo teh apsiln ,ocdr romf snilcuooc of hte oeosrrpit aslpni rrye.ta rOu atietpn ertssnpe twih arscedede nasstnieo to rkipnipc lweob hte velel of teh esnek sa lewl as lwngaki hiwt a eesb-wdadi ,aitg iyklle tniaigndci slos of heT ptiaent si oasl cmiane thwi etrdhpgemysn-ee ipnsethol.ur

mserHgedeptyen lesunhotpir aer iptyaylcl usacde by na iynaltibi to kaem uogenh DNA, eudasc yb a alkc of csaeesnyr preuorcssr nad sitvniam cluiginnd 9B ef)lto(a and 21B (m)onli.baca fI eth tintpea is efloat iefde,cnit we ese vatleede hieyenotocms eniidec.yfc If teh pittena is 21B ,ncietdife we see dvteeael tymmhnocaliel dcai nda yesnocmtheio .vsllee cimpHmiesohyeortenay nca ecasnire bisohmr.ots sbiTmosohr ni het poirtoers iasnpl atreyr anc secua iorertspo crod yen.rodms nI t,noaidid clka of avmiitn 1B2 srpiima lmiyne omanrofit nda dlase to Stcaubue ibmCdeno nireDeegont,a hhcwi fctfsae eht lmanacihotSip rattc nutanco(cig orf dsacredee picnirkp aois)ennst, onsCapiloirtc Tca,rt dna loraDs eloMl-nidauCm sLucnsemi caTrt gnaicncot(u ofr eth deedrcu opoprpitoce.nri

)A rAnriote docr rs-edmnyo sslo of oomrt mcomnda, sa llew sa iaaltlerb lsos of htea nad pa,ni eth patneti ahs not tlos rtoom ,oinunctf so ti tannco be hts.i )B tanlCer rdco dey-rmons etsrspne sa a ibmcnoiatno fo rtomo adn rysesno sl,os luuyals htwi dadblre iu.nsfdoyntc Tsih taitnpe dseo tno sayldip oromt sslo or erdadbl fc.ndionuyts )C rmieHcdo snredoy-m lAos lealdc rdrq,a-nweBouS isht is eeplotcm ijynur to ietreh the lfet ro itghr dies fo teh ipsanl o.drc tI psnsreet iwht omtro ytscuofinnd adn rexfle iftcundnosy ilpsailreytal at the eelvl of teh osenli; slso fo peurp orotm dncmoma owelb teh noeisl lestlliriapay sipat(sc ei)srpas; ssol of asdorl rroiacecd-nmul ntsoaseni syitpaerlilla at dan wbeol eth lonse;i dan ossl fo napi nda umeerearptt aioenstsn neayarrtllotalc 2 to 3 eabrvetr lboew the isoen.l )E eeSgrtmyna dmney-sro a legtoncina auefilr to dpvoele prat fo hte isapnl heT wen seton fo ytomspms ta 28 ysaer old eaksm isth na ulliyken dnagi,

yb_26  amazing, thank you! +  
aisel1787  great explanation +  
rockodude  sensation to pinprick is DCML tract. SCD affects spinocerebellar (not spinothalamic), corticospinal, and DCML. otherwise good explanation. +2  
azibird  Sensation to pinprick is not dorsal column-medial lemniscal tract, it's spinothalamic tract. So this patient has a lesion of the dorsal columns, spinothalamic tract hypersegmented neutrophils, and anemia. What the hell is going on? How is this just posterior cord syndrome? Spinothalamic is not posterior cord. +4  
makingstrides  Like most of these questions, pick the closest/ best answer. For reasons above, this is the best one. +  
skonys  FA19 pg69 says B12 deficiency causes SCD AND parasthesias. This patient has progressive numbness/decreased pinprick, ataxia (spinocerebellar & DCML). Also it's important to remember that B9 and B12 both have megaloblastic anemia but B9 DOESN'T have neurological symptoms. +  

submitted by seagull(1677),
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2B1 cndficyeie slaed ot tdnaleymnioi of hte DLMC dna ASL pwasytah ie(.. ipsreorto ocdr re.ynsdom)

submitted by amarousis(24),
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Btu etsdn'o abcuuest bdcnoeim enoegidnaret aedl to mmeiptrnia ni M,CLD raibsecreleponl adn aoopinccilrts rctta? I etg eth axtcia gait - p.sDrCLlrole/bineceaM uBt het neissoatn ot pkiircpn, ou'dwltn htta eb eht mhitoacsinalp cttar? aTht si otn llausyu decteaff ni ctabeusu ciobdmen tagedonrniee.

krewfoo99  It would affect the dorsal column tract and the spinothalamic tract. It wont affect the spinocerebellar tract (Thus Rombergs sign in B12 deficiency will be positive) All three of the tracts are affected in Friedrichs Ataxia +  
krewfoo99  Sorry. Just checked on FA. It will also affect the spinocerebellar tract +  
spow  Sensation to pinprick is DCML +  
meli  UWORLD ID:65 "many patients develop neurologic manifestations due to: axonal degeneration of the peripheral nerves, leading to numbness, paresthesia, and depressed motor reflexes." So, I think the sensation to pinprick was describing the paresthesia! +  

submitted by masonkingcobra(368),
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ynrsaoelPl my iuses wtih shti otquiens is ttah I hguhot 2B1 cuaess oyminealetnid ni tbho hte LSCT nda hte LCMD CDS)( ubt tehy ear nttiegs teh aemcmisnh eerh llryae hwit eht elwho ltcneoimmyah idac bit dan eht eimdirap meiyln ehstiynss

If ur'eoy ouscrui


submitted by krewfoo99(104),
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Can smeeoon ianelpx waht the uetrpic is uodppses ot wso?h Is it spopdeus ot eb gmstedene nesuliortph?

titanesxvi  yes do to B12 deficiency +  

submitted by cheeseheadkids(15),

I personally feel this question is misleading because the loss of pinprick demonstrates loss of the spinothalamic tract. This is NOT part of subacute combined degeneration due to B12 deficiency.

submitted by titanesxvi(89),
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Hree is a odgo uscreroe