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NBME 22 Answers

nbme22/Block 2/Question#7

A 66-year-old man comes to the physician because of ...

Libido: decreased;
Nocturnal erections: normal

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 +4  upvote downvote
submitted by iviax94(7),

There have been a couple of questions about this topic on the newer exams. I’ve been answering by equating libido to testosterone levels and nocturnal erections to health of vasculature (atherosclerosis or not). Is this correct?

liverdietrying  When you’re thinking of libido, don’t just equate it to testosterone -- make sure you’re always considering depression! Depression following stroke is common, especially with residual physical disability, so this would decrease his libido. Nocturnal erections equate to “does it actually work?” not just the vasculature but the neural input as well. For example, during prostatectomy damage to the pelvic plexus (nerves) can lead to impotence. There’s nothing to suggest that he has vascular or neurologic erectile dysfunction here, which is why his nocturnal erections are intact. +11  
_pusheen_  @liverdietrying Was it premature to assume he has trouble with erections because of neural damage from the stroke? I put low libido, low nocturnal erections. Is it because the stroke resulted in hemiparesis and not autonomic dysfunction or something like that? +3  
liverdietrying  @pusheen Correct, you won’t classically get impotence after a hemiplegic stroke. His inability to achieve an erection is much more likely to be 2/2 psychosocial effects than organic disease. If this vignette instead said that this had gotten a prostatectomy with resulting damage to the pelvic nerves that allow for erection, then it’d be a more safe choice to put no nocturnal erections. +3  
fast44  Is there a video or somewhere that explains these sexual dysfunctions? This seems to be a topic that keeps repeating on the new exams. +1  
forerofore  well, i though that because he had a stroke he would be likely to have atherosclerosis, which would keep libido high and reduce nocturnal erections, i kinda ignored the whole "he´s depressed" part of the vignette despite understanding the mechanism well. but from a clinical depression point of view, if his arteries are intact, and he is depressed, then libido would be low, and erections present at night. +4  
pg32  I can't remember exactly but I swear the question on NBME 21 the guy's wife had died as well...? Or they had gotten divorced? Either way, he had some psychological baggage as well, but his libido was still normal, and the explanation was that his testosterone would be fine regardless of his depressed mood. So I went with that logic here and missed this question. I don't understand how I am supposed to gauge someone's libido based on vague hints at their mood, especially when in one exam mood does not decrease libido and in the other it does. +  
drzed  @pg32 bro spoilers +1  

 +2  upvote downvote
submitted by elf16(2),

How is this different from the question on NBME 21 in which a 68-year old man also had psychogenic ED? But the answer was normal libido and nocturnal erections.

toxoplasmabartonella  In that case, his testosterone was normal and he had no signs of depression. The stem did say his wife passed away few months ago, so i personally chose low libido, but whatever. +  


After getting it wrong (because of the NBME 21 Q), I understood it like this:

– Libido is a long term state, meaning your libido could be fine, but anxiety in that MOMENT might cause psychogenic ED

– This guy has some classic SIG E CAPS criteria going on: fatigue (energy loss), sleep disturbances, concentration problems

– It says he hasn't been able to maintain any erection (vs NBME 21 guy that was able to masturbate (his long term sex drive was OK) but had performance anxiety in the moment)

Therefore, lack of sex drive fueled by depression --> low libido, but physiologically nothing wrong with him --> nighttime erections

 +1  upvote downvote
submitted by nwinkelmann(185),

So, I thought this question was super vague and not great... that being said, having gotten it wrong and not really having a good explanation for the answer, I did a little research and found this article: https://www.ahajournals.org/doi/pdf/10.1161/01.STR.30.4.715

This was the main conclusion: "The results of the present study, aimed at assessing the effects of stroke on sexual functioning, reveal a significant decline in libido, coital frequency, sexual arousal, and satisfaction with sexual life in both stroke patients and their spouses. The present results also demonstrate that disorders of sexual functions are most significantly associated with various psychosocial factors, such as patients’ general attitude toward sexuality, fear of impotence, and ability to discuss sexuality, as well as with the degree of poststroke functional disability. Moreover, sexual dysfunction was related to the presence and degree of depression, diabetes mellitus, and cardiovascular medication. The etiology or location of the stroke and the gender or marital status of the patients were not associated with changes in poststroke sexuality in patients in the present study."

Looking at the question again, I'm guessing the "fatigue and difficulting sleeping and concentrating" statement was supposed to be a clue for depression, especially since it started after his stroke. Also, no physical abnormalities suggest functioning is intact and thus nocturnal erections would be preserved normally. This is just stupid.

ls3076  appreciate this kind of effort to look up journal articles but honestly this is not really what nbme answers is for... we should be able to get the answer from process of elimination/basic science concepts and not from looking up studies as we obviously can't do this on the test +  

Answer = Decreased libido; normal nocturnal erections

I believe what they were trying to indicate in this question was Psychological Sexual Dysfunction (aka - Performance Anxiety).

In this case, it wasn't so much the performance that worried the man, but he may be so focused on his health issues (post stroke), that he is unable to perform adequately. Therefore, his natural libido would be decreased. However, because it's psychogenic & not physiologic, he should still have normal nighttime erections.

Organic ED: normal libido, decreased nocturnal erections

Psychogenic ED: decreased libido, normal nocturnal erections

Got it.

 +0  upvote downvote
submitted by adong(28),

Pretty much if they can masturbate or get it up alone in any way their nocturnal tumescence should be normal meaning that their innervation and reflex pathways are all intact. Libido aka sex drive from what I’ve seen so far is altered by depression. So like in the question on NBME 21 the stem stated that screening for depression was negative which is why libido would also be normal in this case. If there’s ever a Q with a depressed guy and normal lab values and physical exam, most likely gonna be decreased libido with normal night erections - courtesy of /u/diffuseaxonalinjury

 +0  upvote downvote
submitted by ls3076(36),

Is decreased nocturnal erections not possible due to the incongruity between onset of symptoms and stroke (2 mos versus 3)? Agree that these questions are very vague and frustrating. Not sure where to get a good grasp on this material.

Nocturnal penile tumescence measurement (phallography) is a test that measures spontaneous nightly erections in erectile dysfunction (primarily performed in a sleep laboratory). It's useful for differentiating between organic from psychogenic erectile dysfunction.

Vignette describes a possibly depressed patient => psychogenic erectile dysfunction. Since it is not an organic cause of ED, nocturnal erections would be normal. Organic etiologies of ED include neurogenic or vascular.

Libido part confuses me here. Libido means sexual desire or appetite. I was thinking since he's coming in to get ED checked, it indicates he's appetite for sex is enough that it made him get it check. So libido should be normal. Any help?