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NBME 18 Answers

nbme18/Block 3/Question#41

24 yo man, 3 days of progressive numbness of both feet

Myelinated primary afferents

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submitted by spow(7),

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.

Guillain Barre is T-cell mediated destruction of myelinated axons. Generally presents with a rapid onset following a viral / bacterial illness with ascending paralysis.

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  

 -2  upvote downvote
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  https://nbmeanswers.com/exam/nbme18/121#subcomment 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 +