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NBME 21 Answers

nbme21/Block 2/Question#34

A 28-year-old man is brought to the emergency ...

Inferior rectus and inferior oblique

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submitted by soph(16),

its bc this are the only 2 muscles on the orbital floor google orbital floor muscles in google images https://www.google.com/search?q=orbital+muscles&tbm=isch#imgrc=NNOONaLRFuEP1M:

 +2  upvote downvote
submitted by burak(8),

Orbital floor fracture:

1- Infraorbital nerve injury: Numbness and paresthesia of the upper cheek, upper lip, upper gingiva.

2- Entrapment of the inferior rectus muscle: Impaired upward gaze

3- Enophtalmosis

4- Clousing of maxillary sinus: Teardrop sign

Inferior oblique = helps you look up & in.

Also, they said floor of the orbit, so it makes sense that the inferior muscles would damaged.

sahusema  I know you're right. I was just so uncomfortable picking an answer with "inferior rectus" because damage to the inferior rectus does nothing to explain the clinical findings of impaired upward gaze. Unless the muscle is physically stuck and can't relax or something +3  
emmy2k21  Agreed. Why would a dysfunctional inferior rectus contribute to impaired upward gaze??? I eliminated that answer choice and got it wrong :( +1  
dr_jan_itor  in the last sentence it asks you to assume an "entrapment", so it is actually the inferior rectus which is the cause of the upward gaze palsy. The entrapped muscle is functionally trapped in it's shortened position, thereby not allowing the orbit to gaze upward. +5  
chandlerbas  bam! dr_jan_itor just cleaned up that confusion +  

Option A is the only option where both muscles are part of the orbital floor. Also, the last sentence in the question stem is a total modifyer of what one would expect the question to be asking. It is not asking for you to assume that these muscles have been severed, paralyzed, or rendered flacid. It is asking you to assume that they have become "entrapped" if the muscle is entrapped, then it cannot allow the eye to move into whatever position it would be in when the muscle is at its lengthened position. So in this case, It is the inferior rectus being entrapped in a functionally shortened position that is preventing upward gaze.

 +0  upvote downvote
submitted by niboonsh(81),

The obliques do the opposite action of their name. Inferior oblique moves the eye UP and OUT (extortion, elevation, ABduction). Since the question says that there is a fracture involving the orbital floor, that automatically rules out D (medial rectus and inferior oblique), leaving the only logical answer to be the inferior rectus and inferior oblique. https://www.youtube.com/watch?v=lWKkHWWDIEI

aishu007  hi, but inferior oblique moves up and in and not out +  
d_holles  https://www.youtube.com/watch?v=3J2UZiLVZKA In case ppl need a refresher +