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NBME 23 Answers

nbme23/Block 3/Question#39

A 44-year-old woman comes to the physician because ...

Decreased CSF production by the choroid plexus

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 +7  upvote downvote
submitted by hayayah(599),

Carbonic anhydrase inhibitors (eg, acetazolamide) and loop diuretics (eg, furosemide) are thought to exert their effect on ICP by reducing cerebrospinal fluid (CSF) production at the choroid plexus.

Google says mechanism is unknown LOL.

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 +2  

 +1  upvote downvote
submitted by uslme123(19),

This question makes no sense to me. She has an extremely low opening pressure yet has signs of increased intracranial pressure. Did they mean to put 32 cm H20?????????

uslme123  Standard lab values are incorrect, way to go NBME. +2  
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. +2  
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. +  
donttrustmyanswers  Does anyone have clarification on this question? +  

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."

 +0  upvote downvote
submitted by whoissaad(39),

HCO3- is needed to make CSF. Acetazolamide inhibits carbonic anhydrase and decrease HCO3- absorption from renal tubules.

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 +