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NBME 24 Answers

nbme24/Block 2/Question#18 (37.4 difficulty score)
A 68-year-old man has loss of pain and ...
Right dorsolateral medulla🔍
tags: FA20p504 

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submitted by m-ice(326),
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heT itpneta hsa loss fo ipan nda ueermatprte on eth grhti iesd of ish oasneinSt of eht ecaf si lae,lripaits os teh siuse stum be on the atniep'st trihg ,seid hwhci ew acn mofirnc yb nnoiwkg hatt eatosnsni fo het oybd is elaortatnacrl, dan he hsa sotl eltf sidde ipna nda terptmuaree fo eth obd.y

niaP and teurepramet nassoinet fo eth dybo is ptra of hte anoplitcamihs tatc,r hiwhc ywasla rsnu lteylalra hogrhut eht eisn.brmat Tshi nac be fcemiordn by rbreieegnmm ttha insanesot ot hte aecf lsao usnr ertyaalll rothguh teh .abmrntsei o,S ew acn nfiorcm hsti si a rihgt ideds aetllra nmtrsbeai ssei.u

Teh sosl of gag lfxere and asraplsiy fo teh alcov sordc lmypi mpmirnaeti fo naacirl esenvr IX nad X, tboh of hwhci lelcioaz ot teh demalu.l reefTreo,h eht eraswn is ightr olodtararsel mdl.leau

duat98  You're a good man. +2  
charcot_bouchard  You must be handsome too +7  

submitted by brethren_md(88),
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Lertala uyrledlaM ryndSoem ba(lnWrle)ge - ees AF for omer a.liteds tsompySm fro ihst mnseydor amhct up wthi htwa si enigb

submitted by charcot_bouchard(391),
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I gte hwy tsi laartel utb todn lla rniacal vnere eecpxt 4 earsi arelnVlyt? TWF tyeh add shti rDoso eferbo terla?la

qfever  I think it's the nucleus affected in lateral medullary syndrome (instead of the nerve axons) +  
nerdstewiegriffin  Because in the medulla section the nucleus is dorsal motor nucleus of X +  

submitted by cassdawg(960),

"Simple rules of the brainstem" (credit to our anatomy gods at UofL for organizing, also this image is fucking great for visual learners):

  1. There are 4 structures always in the ‘midline‘ beginning with M
    • Motor pathway (or corticospinal tract): damage results in contralateral weakness of the arm and leg
    • Medial Lemniscus: damage results in contralateral loss of vibration and proprioception in the arm and leg
    • Medial longitudinal fasciculus: damage results in ipsilateral inter-nuclear ophthalmoplegia (failure of adduction of the ipsilateral eye towards the nose and nystagmus in the opposite eye as it looks laterally)
    • Motor nucleus and nerve: damage results in ipsilateral loss of the cranial nerve that is affected (III, IV, VI or XII)

  2. There are 4 structures to the ‘side‘ (lateral) beginning with S
    • Spinocerebellar pathway: damage results in ipsilateral ataxia of the arm and leg
    • Spinothalamic pathway: damage results in contralateral alteration of pain and temperature affecting the arm, leg and rarely the trunk
    • Sensory nucleus of CN V: damage results in ipsilateral alteration of pain and temperature on the face in the distribution of CN V (this nucleus is a long vertical structure that extends in the lateral aspect of the pons down into the medulla)
    • Sympathetic pathway: damage results in ipsilateral Horner’s syndrome, that is partial ptosis and a small pupil (miosis)

  3. The rule of CN 4’s (also found in FA2020 p504)
    • 4 cranial nerves in the medulla (IX-XII)
    • 4 in the pons (V-VIII)
    • 4 above the pons (2 in the midbrain= III, IV, 2 in the cortex= I, II)
    • The 4 motor nuclei that are in the midline are those that divide equally into 12 (except I and II), including III, IV, VI and XII (V, VII, IX and XII are in the lateral brainstem)
cassdawg  Sorry for the formatting fuck up +  
drdoom  @cassdawg best to avoid doing nested lists. website doesn't seem to like that :P better to start a “brand new” list for each little subsection kinda thing :) p.s. congrats on your MVP of the Year Award! +1  

Wow can we talk about how amazing this image is? Thanks for sharing!

+/- motherhen(31),

submitted by abhishek021196(50),

Posterior inferior cerebellar artery [PICA] supplies

  1. Lateral medulla
  2. Nucleus ambiguus (CN IX, X, XI)
  3. Vestibular nuclei
  4. Lateral spinothalamic tract, spinal trigeminal nucleus
  5. Sympathetic fibers
  6. Inferior cerebellar peduncle

Damage to PICA causes Lateral medullary (Wallenberg) syndrome.

Dysphagia, hoarseness, decreased gag reflex, hiccups. Vomiting, vertigo, nystagmus decreased pain and temperature sensation from contralateral body, ipsilateral face. Ipsilateral Horner syndrome. Ipsilateral ataxia, dysmetria.

Nucleus ambiguus effects are specific to PICA lesions.

“Don’t pick a (PICA) horse (hoarseness) that can’t eat (dysphagia).” Also supplies inferior cerebellar peduncle (part of cerebellum).

submitted by welpdedelp(219),
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sihT wsa treaall dlraulme yrsoemdn aak loatrldsraeo tinarcf of the .CAPI