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NBME 18 Answers

nbme18/Block 3/Question#41 (23.9 difficulty score)
24 yo man, 3 days of progressive numbness of ...
Myelinated primary afferents🔍

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submitted by spow(24),

Here's how I thought through this. problem with DCML (absent proprioception and vibration sense), problem with deep tendon reflexes (DRGs), ataxic gait (spinocerebellar pathway), mild weakness (motor neurons). The only thing that all of these pathways have in common is that they all use myelinated afferents.

I don't know if Guillan Barre would actually present like this, but you don't have to know what the illness is to figure the question out.

queestapasando  Might be acute inflammatory demyelinating polyradiculopathy (FA 2019 p.512): "Most common subtype of Guillain-Barré syndrome. Autoimmune condition that destroys Schwann cells via inflammation and demyelination of motor fibers, sensory fibers, peripheral nerves..." +1  
md_caffeiner  sounds really great, and i thought the same and answered the same way. but while in the exam, i had that "how THE FUCK could motor weakness be an afferent??" moment. quite frequently forget the fact that this is an nbme full of mess. lol. +  

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ilGnialu rrBea si cl-elT emddiaet deocrusntit fo nmdlaietey nas.ox Gnyelrale prtessen wthi a apidr stnoe iowlnfolg a irlva / actelarib ieslsln htiw nicgesnda aripayls.s

Is this Guillain barre though? I felt it was Acute inflammatory demyelinating polyradiculopathy, discussed on page 512 FA 2019.

There is no relation to C jejuni here nor does the patient have any other relations to infection such as eating something or etc.

wishmewell  Acute inflammatory demyelinating polyradiculopathy is a subtype of GBS. +1  

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submitted by tamey(0),

i think this is vitamin B12 deficiency as it causes demyelination of spinocerebellar tract (ataxic gait),corticospinal tract(weakness),DC/ML(loss of vibration and propreoception)

wishmewell b12 deficiency is slowly progressive it wouldn't happen in 3 days, also b12 deficiency leads to hyper reflexia. and you would also see spastic paralysis in b12 deficiency +