NBME 23 Decreased CSF production by the choroid plexus (NBME Answers)

NBME 23 Answers

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

+10 upvote downvote
submitted by ∗hayayah(1212)

get full access to all content ⋅ pick a username

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.

get full access to all content ⋅ pick a username

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 +4

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. +5

+5 upvote downvote
submitted by ∗uslme123(86)

get full access to all content ⋅ pick a username

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?????????

get full access to all content ⋅ pick a username

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. +4

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 +1

tyrionwill Hi, mjmejora, MRI did not see anything abnormality, couldn't this mean that there was no obstruction in the ventricles? +1

+2 upvote downvote
submitted by motherfucker(6)

get full access to all content ⋅ pick a username

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."

get full access to all content ⋅ pick a username

+1 upvote downvote
submitted by ∗usmile1(154)

get full access to all content ⋅ pick a username

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.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315016/

get full access to all content ⋅ pick a username

+1 upvote downvote
submitted by ∗handsome(3)

get full access to all content ⋅ pick a username

fa 2020 pg 527 You'll see IDIOPATHIC INTRACRANIAL HYPERTENSION

Also called pseudotumor cerebri. INCREASE ICP with no obvious findings on imaging. Risk factors include female sex, Tetracyclines, Obesity, vitamin A excess, Danazol (female TOAD).

Treatment: weight loss, acetazolamide, invasive procedures for refractory cases (eg, CSF shunt placement, optic nerve sheath fenestration surgery for visual loss

get full access to all content ⋅ pick a username

medb FA 2020 pg 521** under idiopathic intracranial hypertension +

+0 upvote downvote
submitted by ∗whoissaad(102)

get full access to all content ⋅ pick a username

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

get full access to all content ⋅ pick a username

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 +

Must-See Comments from nbme23

ferrero on Precapillary resistance
yotsubato on 99%
sne on Triglyceride
sajaqua1 on Area labeled ‘D’ (Spinothalamic tract, right)
stinkysulfaeggs on Hypoglycemia
hayayah on Iris
soph on Peak inspiratory pressure (alveolar): ...
seagull on Area labeled ‘C’ (Cranial nerve 8: ...
water on Dietary change
wired-in on 28.8
beeip on Binding of permeable ligand to nuclear ...
thomasalterman on Hypoglycemia
yotsubato on Inhibition of the cytochrome P450-dependent ...
seagull on Decreased sodium bicarbonate reabsorption in ...