need help with your account or subscription? click here to email us (or see the contact page)
join telegramNEW! discord
jump to exam page:
search for anything ⋅ score predictor (โ€œpredict me!โ€)

You must be logged in to vote!
Retired NBME 18 Answers

nbme18/Block 3/Question#41 (reveal difficulty score)
24 yo man, 3 days of progressive numbness of ...
Myelinated primary afferents ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
tags: neuro repeat

 Login (or register) to see more


 +10  upvote downvote
submitted by โˆ—spow(50)
get full access to all contentpick a username

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.

get full access to all contentpick a username
queestapasando  Might be acute inflammatory demyelinating polyradiculopathy (FA 2019 p.512): "Most common subtype of Guillain-Barrรฉ syndrome. Autoimmune condition that destroys Schwann cells via inflammation and demyelination of motor fibers, sensory fibers, peripheral nerves..." +5
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. +6
2059nyc  It could be explained by the lack of the sensory component for the DTR and not the motor neurons? +2
sonofarathorn  I focused on the loss of vibration and joint position sensation. Pacinian corpuscles sense vibration. Meissner corpuscles and Merkel discs sense position. These sensory receptors are all large myelinated afferents FA 2019 p.482 +2
mgadda  the question asks the most likely explanation for the SENSORY findings +6
aaftabsethi1  Can anyone explain numbness and tingling ? Isnt that through unmyelinated fibres? +1
cassdawg  @aaftabsethi unmyelinated afferents include fibers that carry: slow pain, heat, and olfactory senses. +

  • GBS is an inflammatory demyelinating polyneuropathy affecting motor and sympathetic efferent fibers.

  • Sensory afferent fibers are also affected.

  • It presents with acute, ascending bilateral muscle weakness, sensory loss, and Hyporeflexia.


You must be logged in to vote!

 +3  upvote downvote
submitted by โˆ—sympathetikey(1600)
get full access to all contentpick a username

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

get full access to all contentpick a username
jbrito718  Autoantibodies are against GM1 gangliosides on myelin! +


You must be logged in to vote!

 +0  upvote downvote
submitted by โˆ—amirmullick3(76)
get full access to all contentpick a username

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.

get full access to all contentpick a username
wishmewell  Acute inflammatory demyelinating polyradiculopathy is a subtype of GBS. +7


You must be logged in to vote!

 +0  upvote downvote
submitted by โˆ—godby(2)
get full access to all contentpick a username

Motor + Sensory + rapid progress :: may be R/O Acute inflammatory demyelinating polyradiculopathy

get full access to all contentpick a username


You must be logged in to vote!

Must-See Comments from nbme18

feliperamirez on He is medically qualified to drive
anechakfspb on Tubular atrophy
aneurysmclip on Endothelial nitric oxide synthase production
azibird on 24,25-Dihydroxycholecalciferol
famylife on Increased transcription of HMG-CoA reductase
match95 on Plasmid loss
apurva on Antineoplastic
cbreland on Basement Membranes
match95 on Proximal tubule: isotonic; Macula densa: ...
sugaplum on Abnormal migration of endoderm from the ...
amirmullick3 on Myelofibrosis
merpaperple on Primary spermatocyte
wishmewell on Alpha-synuclein
namira on Greening reaction on blood agar

search for anything NEW!