FA says that it does NOT result from an increase in subarachnoid space volume. But goljan lists that it does result in an increased subarachnoid space vol. I get that the fibers stretch and the stretching of the fibers causes the incontinence and neuro symptoms but how do the fibers stretch in the first place. it has to be to increased CSF vol right? God i effing hate FA sometimes!
normal pressure hydrocephalus
- Thread starter EazyE1907
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Subarachnoid space includes the ventricles b/c they include CSF, correct? If so then wouldn't it have to be an increase? I just thought that it was normal pressure because the ventricles accommodate for the extra CSF
I could be wrong on this so feel free to correct cuz i'd like to know as well!
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Goljan is right. What version of First Aid are you using? FA 2013 says there is an increase in subarachnoid space volume, but CSF pressure is not elevated....which is correct and does not contradict Goljan.
Like you said, in normal pressure hydrocephalus, there is reduced absorption of CSF via the arachnoid villi, so CSF volume increases. It is a specific case of communicating hydrocephalus where the ventricles enlarge to accommodate the increase in CSF volume. The pressure appears "normal" and you dont get typical clinical signs of high pressure hydrocephalus like papilledema because of the ventricular enlargement buffering the increased CSF volume. The enlargement of the ventricles is what causes the adjacent cortical fibers to stretch and hence the unique "wet, wacky and wobbly" effect.
Like you said, in normal pressure hydrocephalus, there is reduced absorption of CSF via the arachnoid villi, so CSF volume increases. It is a specific case of communicating hydrocephalus where the ventricles enlarge to accommodate the increase in CSF volume. The pressure appears "normal" and you dont get typical clinical signs of high pressure hydrocephalus like papilledema because of the ventricular enlargement buffering the increased CSF volume. The enlargement of the ventricles is what causes the adjacent cortical fibers to stretch and hence the unique "wet, wacky and wobbly" effect.
hey thanks for the detailed explanation. i am using fa 2014 and it says exactly " Does not RESULT in increased subarachnoid space volume"then it goes on to talk about ventricle expansion and bla bla bla. i mean is it their choice of words that i am getting stuck at. regardless i get the big picture and i have answered similar questions of this pathology correct on qbanks and nbme's but fa really pisses me off sometimes. I'm the type to spend 30 mins on that **** and look at different resources to make sure it's right. i don't want any confusion come test day.
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I don't have my Goljan any more but you're saying two very different things. The stretching of the fibres in NPH results from ventriculomegaly, whether or not there is associated subarachnoid expansion. In NPH, the ventricles and subarachnoid spaces communicate, and the problem is thought to be at the arachnoid granulations, i.e after the subarachnoid space. Indeed, NPH can result in subarachnoid expansion, but it results from ventriculomegaly.
American Journal of Neuroradiology said:
Just to be clear, it may or may not result in significant subarachnoid expansion but the key fact for the USMLE is that ventriculomegaly is the cause for the fibres stretching that they ask about.
