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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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submitted by sattanki(32),

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. +  
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! +  
baconpies  peripheral nerves would include motor & sensory, whereas LMN would be just motor +6  
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. +  

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submitted by guillo12(23),

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


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submitted by tinydoc(63),

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.

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)? +