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NBME 24 Answers

nbme24/Block 2/Question#35

A 55-year-old woman comes to the physician because ...

Lower motoneurons

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 +3  upvote downvote
submitted by tinydoc(133),

I don't think it matters whether or not this was ALS ( which I still think it is). But theres fasiculations and Weakness and atrophy those are LMNL signs. Theres sooo many sneaky questions in this exam, this isnt one of them.

 +2  upvote downvote
submitted by sattanki(46),

Does anyone have any idea on this question? Thought it was ALS.

ankistruggles  I thought it was ALS too (and I think it still could be?) but my thought process was that a lower motor neuron lesion would be the more specific answer. +1  
sattanki  Yeah makes sense, just threw me off cause ALS is both lower and upper motor neuron problems. Corticospinal tract would have been a better answer if they described more upper motor neuron symptoms, but as you said, they only describe lower motor neuron symptoms. Thanks! +1  
mousie  Agree I thought ALS too but eliminated Peripheral nerves and LMN because I guess I thought they were the same thing ....??? Am I way off here or could someone maybe explain how they are different? Thanks! +1  
baconpies  peripheral nerves would include motor & sensory, whereas LMN would be just motor +9  
seagull  Also, a LMN damage wouldn't include both hand and LE unless it was somehow diffuse as in Guil-barre syndrome. It would likely be specific to part of a body. right??? +  
charcot_bouchard  No. if it was a peri nerve it would be limited to a particular muscle or muscles. but since its lower motor neuron it is affecting more diffusely. Like u need to take down only few Lumbo sacral neuron to get lower extremity weakness. but if it was sciatic or CFN (peri nerve) it would be specific & symptom include Sensory. +  
vulcania  I think it's ALS too. The correct answer choice here seems more based on specific wording: the answer choice "Corticospinal tract in the spinal cord" wouldn't explain the tongue symptoms, since tongue motor innervation doesn't involve the corticospinal tract or the spinal cord (it's corticobulbar tract). This is a situation of "BEST answer choice," not "only correct answer choice." +  

 +1  upvote downvote
submitted by rainlad(8),

I was thrown off because I didn't realize lower motoneuron = lower motor neuron face palm

"LMN deficits... dysarthria, dysphagia, asymmetric limb weakness, fasciculations, atrophy

UMN deficits... pseudobulbar palsy (i.e. dysarthria, dysphagia, emotional lability, spastic gait, clonus])"

-- FA 2019 p.518

 +1  upvote downvote
submitted by guillo12(31),

"The loss of lower motor neurons leads to weakness, twitching of muscle (fasciculation), and loss of muscle mass (muscle atrophy)".


I treated this like Werdning Hoffman/SMA ("tongue fasciculations"), and just kind of accepted it being weird to be in a 55-year-old.

dr.xx  SMA4 (Adult-onset)? +