hydrocephalus

[coconut lime]

i just had a kaplan question about a baby born with a large head; ultrasound reveals hydrocephalus and marked enlargement of the lateral ventricles. it goes on to ask which site the obstruction most likely occurred at. answer choices:

a) aqueduct of sylvius
b) foramen of luschka
c) foramen of magendie
d) subarachnoid space near brainstem
e) subarachnoid space near cerebral hemispheres

and i know that the foramina of monro drain the lateral ventricles into the 3rd ventricle, so i crossed off answers a-c because those drain the 3rd and 4th vent, respectively. i decided to go with e, because that would be closest to the lateral ventricles.

however, the correct answer was aqueduct of sylvius, because it is apparently the most common site of obstruction. but wouldnt this present with enlarged third ventricles, not enlarged lateral? also, what exactly does an obstruction of the subarachnoid space mean?

thanks!!

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[Idiopathic]

obstruction of the subarachnoid space will inhibit reabsorption and will cause a non-communicating hydrocephalus. The most common cause of hydrocephalus in a kid is structure at the aqueduct of sylvius. I think the lateral ventricles are so malleable that hydrocephalus will affect them more than the third ventricle. I havent seen many cases of dilated third ventricles, since it is so narrow...the pressure always backs up.

 

[marchiafava]

Idiopathic, you need to review your Neuro. You shouldn't give advice and knowledge to others when you don't know it yourself.

Communicating hydrocephalus means the ventricles of the brain communicate, or pass along, the CSF to the surface of the brain. The obstruction of CSF flow occurs not within the ventricles, but within the subarachnoid spaces of the brain. Communicating hydrocephalus can also be the result of a meningeal inflammation, such as an infection, or by blood or tumor cells in the subarachnoid spaces.

Non-communicating, or obstructive, hydrocephalus is caused when there is an obstruction in the flow of CSF within the ventricular system of the brain, including the outlets of the fourth ventricle (the foramina of Luschke and Magendie). The most common place for the non- communicating CSF obstruction is in the aqueduct of Sylvius (also known as aqueductal stenosis). However, the obstruction can also occur in the outlets of the fourth ventricle and from the lateral ventricles into the third ventricle at the foramina of Monro.

An example of non-communicating hydrocephalus is stenosis (or blockage) of the aqueduct of Sylvius. This blockage causes non-communicating hydrocephalus by not permitting CSF to flow from the third to the fourth ventricle. When the obstruction is located in the ventricular system, it causes the ventricles to expand as a result of the accumulation of CSF. Non-communicating hydrocephalus is the most common form of hydrocephalus in fetuses.

Any other questions?

 

[Willamette]

Idiopathic, you need to review your Neuro. You shouldn't give advice and knowledge to others when you don't know it yourself.

Communicating hydrocephalus means the ventricles of the brain communicate, or pass along, the CSF to the surface of the brain. The obstruction of CSF flow occurs not within the ventricles, but within the subarachnoid spaces of the brain. Communicating hydrocephalus can also be the result of a meningeal inflammation, such as an infection, or by blood or tumor cells in the subarachnoid spaces.

Non-communicating, or obstructive, hydrocephalus is caused when there is an obstruction in the flow of CSF within the ventricular system of the brain, including the outlets of the fourth ventricle (the foramina of Luschke and Magendie). The most common place for the non- communicating CSF obstruction is in the aqueduct of Sylvius (also known as aqueductal stenosis). However, the obstruction can also occur in the outlets of the fourth ventricle and from the lateral ventricles into the third ventricle at the foramina of Monro.

An example of non-communicating hydrocephalus is stenosis (or blockage) of the aqueduct of Sylvius. This blockage causes non-communicating hydrocephalus by not permitting CSF to flow from the third to the fourth ventricle. When the obstruction is located in the ventricular system, it causes the ventricles to expand as a result of the accumulation of CSF. Non-communicating hydrocephalus is the most common form of hydrocephalus in fetuses.

Any other questions?

Aside from the somewhat stinky manner of the first two sentences, I must say "Well said Marchiafava."

Willamette

 

[coconut lime]

thanks for the answer, machia. what is it called if the hydroceph. is due to increased production of CSF?

 

[BrooklynDO]

thats the communicating kind

 

[marchiafava]

That's correct, it is part of the communicating entity. Normal CSF production is 0.20-0.35 mL/min; a majority is produced by the choroid plexus, which is located within the ventricular system, mainly the lateral and fourth ventricles. The capacity of the lateral and third ventricles in a healthy person is 20 mL. Total volume of CSF in an adult is 120 mL. Keep in mind though, overproduction hydrocephalus is EXTREMELY RARE.

 

[mjl1717]

1)Lighten up on Idiopathic, he's been more helpful on this forum then 3 or 4
regular med students or "doctors to be" combined (no matter who they are)
2) Its not what ya say but how you say it. [One way not to get sued is to have a GOOD rapport with your patients-supposedly]
3)Thx for the info.
4)Humans do make mistakes.

 

[Idiopathic]

I did make a mistake on non-communicating, and for that I apologize. Marchiafava was ever so kind as to point that out. Of course he had his book handy when he did it, which is nice. Sometimes we just make typos.

Of course, I would have point it out if anyone else did it, so I cant complain too bad. But you should really check out the body of work before you slam someone

 

[coconut lime]

does an obstructing hydrocephalus also cause enlarged ventricles?