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NBME 23 Answers

nbme23/Block 3/Question#39 (36.0 difficulty score)
A 44-year-old woman comes to the physician ...
Decreased CSF production by the choroid plexus🔍

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submitted by hayayah(1000),
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Caocbrni ardhyanse thorbsiiin g(e, o)timeclaeadza adn oplo iscriuted g,(e imusf)deroe are tgthohu to xeert tireh efectf no CIP by denguric lrcnariespobe fuldi F(S)C oucorpdtin at teh iohcrdo uplxe.s

ogloGe asys ehcainmsm si onknwun LO.L

usmleuser007  Just FYI: Mannitol can also be used to reduce ICP by drawing free water out of CNS Howeveer, it can cause hypernatremia, pulmonary edema, and expansion of ECV can exacerbate heart failure +3  
jimdooder  I think a good way to remember this is that CA inhibitors have very similar effects in the eye (reducing production of aqueous humor) as they do in the ventricles (decrease production of CSF). Can't say I totally understand the mechanisms but thats the connection I made. +2  

submitted by uslme123(52),
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Tish utenioqs mesak on essen ot .me Seh ash na lyeterxme wlo nienpog sesruerp yte ash nssig of aiensderc cilaairnntra pers.erus idD eyth amne ot tup 23 cm H???0?????2?

uslme123  Standard lab values are incorrect, way to go NBME. +3  
wutuwantbruv  I think they mean to put mm Hg. Normal CSF pressure is about 100-180 mm H20 which equates to about 8-15 mm Hg. +3  
alexb  I lost a bit of time wondering about that ugh lol +1  
mjmejora  I thought there must be an obstruction in the ventricles somewhere preventing csf from getting to the spine. so pressure is low in spinal tap but in the head it must be really high. +2  
donttrustmyanswers  Does anyone have clarification on this question? +  
llamastep1  Pseudo tumor cerebri can have normal ICP. Who knew +  
tyrionwill  Hi, mjmejora, MRI did not see anything abnormality, couldn't this mean that there was no obstruction in the ventricles? +1  

submitted by motherfucker(5),

MedScape: "Acetazolamide (ACZ) and furosemide (FUR) treat posthemorrhagic hydrocephalus in neonates. Both are diuretics that also appear to decrease secretion of CSF at the level of the choroid plexus."

submitted by whoissaad(67),
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OH3-C is eedned ot mkae FCS. mAateeaidlzco bihsniti ccnaorbi sarneyahd adn edaecers 3OC-H bontaorips fmro arnel .betsuul

mario  could be pseudo tumor cereberi, ttt is also acetazolamide and is more common in female obese BMI 35KG/M +  
mario  opening pressure could be normal in pseudo tumor cereberi +  

submitted by usmile1(86),

In patients with IIH treated with acetazolamide, the inhibition of carbonic anhydrase in the choroid plexus results in a reduction of CSF production and flow. The acid–base status of the patient may also alter the distribution of acetazolamide in the CSF and brain, but its effect on the CSF flow is secondary to that mediated by the choroid plexus. Based on the pharmacology and distribution of acetazolamide and carbonic anhydrase in the brain, the theory that emphasizes the effect of acetazolamide on CSF production in IIH is most likely primary and direct, and weight loss, when recognized as a factor, is secondary and indirect, and frequently the result of toxic doses in excess of the amount needed for complete enzyme inhibition.