dandy walker vs. arnolf chiari II? Renal Calc.?

[TJDoc7]

Hello....i'm currently 26 days from taking step 1, generally doing okay but two things (one specific, other more general) tend to always give me trouble. wanted to see if there was anyone who maybe had a good way of remembering, clearing them up.

1) Dandy-walker, arnold chiari II formations...know the general principles behind it, have read it god knows how many times in first aid (which in my opinion doesn't differentiate the two well enough) and also checked books...but to sum up...how do you remember it well enough/how they would present it in a test situation (assuming they're not telling you the direct herniations, details). I guess what i'm asking, what's the best way to differentiate the two?

2) My renal physio has always been pretty weak (something which I am spending extra time on for the step), and I have built a pretty good understanding of the princples, ideas and overall understanding of what is emphasized/important...now my mental block is I tend to know the concepts and everything, then get some question (as I'm sure I will) with a bunch of lab values, PAH, flow rates, etc...and my mind goes BLACK dealing with the god knows how many calculations there are for it. Obviously need to know the very basic calculations/understading, but aside from going back, working through problems, and given around 4 weeks out, I have started to just look at the normal values as opposed to plugging in numbers to a calculation for major renal function (gfr, rpf, ff, rbf, etc...) in an attempt to tackle these types of problems from a "answer higher than/lower than/normal" approach (for example problems says "normal person", just assuming all the values like grf, ff, rpf, etc...are their normal values...similarly changing that number given the circumstances they provide). I tend to think (could obviously be wrong) that this is how practicing doctors do it (know the normal numbers cold and adjust it based on that scenario), but would this method hold up on the step? Have they kind of accounted for this in anyone's opinion? Has anyone had similar difficulties, or been using this approach all along?

Thanks for time and help. Apreciate it.

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[rem6775]

In terms of Dandy-Walker and Chiari II there are some pretty important differences.

Dandy-Walker has an enlarged posterior fossa with no cerebellar vermis (or minimal) and in its place a large cyst which is basically a dilated fourth ventricle lined by what you'd expect (ependymal cells). Along with this may come problems with brainstem nuclei (as you might guess). There may be hydrocephalus as well.

Chiari II has a small posterior fossa (instead of large, like in DW) and there is a vermis, it is simply herniated through the foramen magnum. Perhaps more important to remember is the associations between Chiari II and hydrocephalus and a lumbar myelomeningocele (as well as other things like aqueductal stenosis, hydromelia, heterotopias).

So you might pick up the associated conditions (dysplasia of brainstem nuclei for DW and lumbar myelomeningocele/hydrocephalus in Chiari II) in a stem (or they might expect you to make these jumps). You can see that some of the structural differences are quite obvious (large v. small posterior fossa; absent vermis v. herniated one). If you know those distinctions, it should be easy to distinguish the two.

 

[IM Substance P]

Hello....i'm currently 26 days from taking step 1, generally doing okay but two things (one specific, other more general) tend to always give me trouble. wanted to see if there was anyone who maybe had a good way of remembering, clearing them up.

1) Dandy-walker, arnold chiari II formations...know the general principles behind it, have read it god knows how many times in first aid (which in my opinion doesn't differentiate the two well enough) and also checked books...but to sum up...how do you remember it well enough/how they would present it in a test situation (assuming they're not telling you the direct herniations, details). I guess what i'm asking, what's the best way to differentiate the two?

2) My renal physio has always been pretty weak (something which I am spending extra time on for the step), and I have built a pretty good understanding of the princples, ideas and overall understanding of what is emphasized/important...now my mental block is I tend to know the concepts and everything, then get some question (as I'm sure I will) with a bunch of lab values, PAH, flow rates, etc...and my mind goes BLACK dealing with the god knows how many calculations there are for it. Obviously need to know the very basic calculations/understading, but aside from going back, working through problems, and given around 4 weeks out, I have started to just look at the normal values as opposed to plugging in numbers to a calculation for major renal function (gfr, rpf, ff, rbf, etc...) in an attempt to tackle these types of problems from a "answer higher than/lower than/normal" approach (for example problems says "normal person", just assuming all the values like grf, ff, rpf, etc...are their normal values...similarly changing that number given the circumstances they provide). I tend to think (could obviously be wrong) that this is how practicing doctors do it (know the normal numbers cold and adjust it based on that scenario), but would this method hold up on the step? Have they kind of accounted for this in anyone's opinion? Has anyone had similar difficulties, or been using this approach all along?

Thanks for time and help. Apreciate it.

Re: #2

Do NOT memorize any renal equations for Step 1. If you know that eGFR is basically some constant divided by the serum creatinine, you'll be totally fine.

I have always trusted my impulse on renal questions. If they give you a creatinine of 1.6, you should know that's abnormally high. If they give you a creatinine of 5.5, you should know that number is through the roof.

Otherwise, I would not waste time or brain space memorizing formulas. When the question writers want you to know a lab value is high, they will make it obviously high.