NBME 21 Loss of sensation to vibration over both feet (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 1/Question#50 (reveal difficulty score)
A photograph is shown of a myelin-stained ...
Loss of sensation to vibration over both feet 🔍 / 📺 / 🌳 / 📖
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submitted by ∗haliburton(224)

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this is a cervical spinal cord section. the cuneate fasciculus is intact (UE) vibration and proprioception, but the white section is the gracile fasciculus (LE) and is damaged. I think the lateral portion that is uneven is just natural/artifact.

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arezpr thorax section +3

guillo12 How do you know the gracile fasciculus is damage?!?! +2

cr which parte of the image its damage?, the pink? or black? +

usmile1 the pink park yes +2

d_holles If you look at https://en.wikipedia.org/wiki/Gracile_fasciculus#/media/File:Spinal_cord_tracts_-_English.svg you can see that the closer to the center = legs, while further away = arms. +4

hyperfukus i still don't see where the damage is lol! FML +2

hyperfukus i finally figured it out lol that was a slow moment i hope im not this slow on step yikes! +1

angelaq11 @hyperfukus I had the same problem at first, marked it and then came back. If you remember, in the spinal cord the white matter and gray matter are "reversed" compared to the brain. That said, if the butterfly shaped region (ie, the gray matter) is colored (in this case) lilac and the rest (ie, white matter) is blackish, the only thing that is actually abnormal, is the region where the dorsal columns are, because it stains just like the normal gray matter. After that, you have to think about which fasciculus is damaged, the gracilis or the cuneatus. The gracilis is medial while the cuneatus is lateral (picture someone with glued legs and open arms). Hope this helped +16

azharhu786 Gracilus Fasciculus = Graceful legs +1

icedcoffeeislyfe Check out FA2020 pg 508 Put simply--> myelin= black --> color of the normal white matter no myelin= pink --> color of the normal gray matter and the damaged area Dorsal columns= vibration, proprioception, pressure fine touch F. graciLis= Lower body F. cUtaneous= Upper body +2

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submitted by ∗h0odtime(54)

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Thoracic Cross Section Reference

Stem clue: Loss of vibration sense = Dorsal Columns
Image clue: pink (damaged) ventral horn area = gracile fasiculus (lumbar + sacral)
Gracile fasciculus in the dorsal column/medial lemniscus tracts carries information from the lower parts of the body (from T6 & below)

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kacook1322 There is no stem clue as to loss of vibration sense +2

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submitted by ∗ragacha(17)

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PAGE 492 FA 2018 DAMAGE IN DORSAL COLUMN (funtion are: pressure, vibration, fine touch, proprioception) SYNAPSE 1 : N. graciLe ( Lower body, Legs) AND N. cUneatus (Upper body, arms)

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nor16 Cuneatus = Cervical, write into columns CG ( fron left to right) Cuneatus, Gracilis (CG) +1

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submitted by swagcabana(8)

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This is showing demylination/disruption (presumably from the spinal cord injury) of the fasciculus gracilis at the level of the lower thoracic cord. You can tell this is the thoracic cord because of the presence of the intermediate horn and the smaller ventral horns. It is the lower thoracic cord (below T5) because there is only one dorsal column.

We have only enough information to conclude lower leg involvement so loss of sensation to vibration over both feet is the best answer.

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submitted by euphoria(1)

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check this link out, here the picture is very clear.

http://learn.chm.msu.edu/NeuroEd/NOP552/files/Atlases/humanatlas/spinalcordatlas/cervical.html

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submitted by ∗icedcoffeeislyfe(56)

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Check out FA2020 pg 508 Put simply--> myelin= black --> color of the normal white matter no myelin= pink --> color of the normal gray matter and the damaged area

Dorsal columns= vibration, proprioception, pressure fine touch F. graciLis= Lower body F. cUtaneous= Upper body

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submitted by ∗paperbackwriter(161)

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I had no clue where the damage was either, but with that said:

You feel the grass with your feet ––> gracilus

And the arrangement along the spinal cord is similar to the sensory/motor homunculus of the brain where the feet are on the inside/medial and the arms are on the outside/lateral.

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drzed Only in the dorsal columns; this is reversed if the decussation happens within the spinal cord (e.g. the spinothalamic tract has a somatotropic distribution where the proximal extremities are medial) +

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