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NBME 22 Answers

nbme22/Block 3/Question#19

A 42-year-old man comes to the physician because of ...

Sensory neuropathy

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submitted by k_tron_3000(21),

The description of bilateral lower limb loss of vibration implies DCML damage, and the absent DTRs + Romberg seem to me to be implying that he possibly has tabes dorsalis from syphilis (or something very similar in presentation).

As for the other answers, A is wrong because his motor function is intact, B is wrong because pain and temperature deficits are not mentioned, C is wrong because it implies a specific nerve is entrapped, but he has lost bilateral sensation in his entire lower extremities

D is the trickiest, and I’m not 100% sure, but I would think radiculopathy of the anterior (ventral) roots would cause motor deficits since they carry motor efferents. You might also expect that motor dysfunction to be unilateral, since it would be unlikely to have a problem with the nerve roots on both sides. also the DCML is not located near the anterior roots of the spinal cord, so if the anterior roots were affected you really wouldn’t expect to see vibratory loss.

So basically process of elimination, I do feel like sensory neuropathy is an extremely vague answer though and I wasn’t a fan of the question.

keycompany  This is a great rationale. I would like to add on that D is wrong because Radicular Neuropathy of the anterior lumbar roots would (1) be painful [radicular neuropathy is characterized by radiating pain (hence the word “Radicular”); this patient has numbness and tingling, not pain] and (2) because the anterior lumbar roots are the motor roots and do not carry sensory innervation. This patient is having a problem with his dorsal spinal cord (not anterior/ventral). +12  
hello  Want to clarify that "radiculopathy" is not synonymous with pain. Radiculopathy can cause pain, weakness, or numbness. I think the only reason Choice D. was incorrect because it discussed the "anterior lumbar roots", which would affect motor function. +7  
niboonsh  Radiculopathy is damage to the actual nerve itself, wouldnt that make it a LMN lesion and babinski would be negative? +1  
link981  Great explanation guys +  
usmel2020  UW QID: 12035 explains what you are testing with Romberg sign +