NBME 22 Sensation from the anterior surface of the scrotum (NBME Answers)

Retired NBME 22 Answers

nbme22/Block 2/Question#11 (reveal difficulty score)
A 52-year-old man comes to the physician ...
Sensation from the anterior surface of the scrotum 🔍 / 📺 / 🌳 / 📖
tags: anatomy

+16 upvote downvote
submitted by ∗d_holles(218)

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I got this one via process of elimination. Not sure how you are supposed to remember all that shit.

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+9 upvote downvote
submitted by socialismkills(9)

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From KenHub.com

Lumbar plexus
Genitofemoral nerve --> Genital branch ==> ANTEROLATEAL surface of scrotum
Ilioinguinal nerve --> Anterior scrotal nerve ==> ANTERIOR surface of scrotum
Sacral plexus
Pudendal nerve --> Posterior scrotal nerve ==> POSTERIOR surface of scrotum
Posterior cutaneous nerve of the thigh --> Perineal branches ==> INFERIOR surface of the scrotum

https://www.kenhub.com/en/atlas/anterior-scrotal-branch-of-ilioinguinal-nerve

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+4 upvote downvote
submitted by ∗hello(429)

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The Q is describing the genitofemoral nerve, which runs on the external surface of the spermatic cord at the superficial inguinal ring

This Q is NOT referring to ilioinguinal nerve -- the ilioinguinal nerve exits THROUGH the superficial inguinal canal whereas this Q is asking about a nerve that is EXTERNAL to the superficial inguinal canal.

See http://www.groinpainclinic.co.uk/data/images/nervesaffected.jpg

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trump2020 This is incorrect. You have it backwards. https://en.wikipedia.org/wiki/Spermatic_cord +4

medjay7 Actually I think @hello is right. First, because that's the only way this shitty wording question makes sense, second cuz it says "that lies on the EXTERNAL SURFACE" that means outside of the spermatic cord, and the genital branch of GF nerve actually does: The genital branch of the genitofemoral nerve enters the inguinal canal via the deep inguinal ring. (https://www.ncbi.nlm.nih.gov/books/NBK430733/), and then exits to innervate the anterior and superior scrotal skin (also the cremaster muscle). +

medjay7 This image explains it better https://www.researchgate.net/figure/The-nerve-sensory-distribution-in-the-groin-area-Adopted-from_fig1_332562049 +

medjay7 CORRECTION: Nevermind, everything I said is wrong. I hate this question +3

chaosawaits After reading all of this, I still have no idea what to believe anymore. I still feel like the Q describes the location of the ilioinguinal nerve with reference to the spermatic cord but the genitofemoral nerve with reference to the sensation. Please help, anyone! +

chaosawaits https://www.instantanatomy.net/abdomen/areas/inguinalregion/spermaticcordcontentsofinguinalcanal.html +

+3 upvote downvote
submitted by ∗meningitis(643)

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Actually, I correct myself: I looked closer and the Genito femoral has an external Spermatic branch and a Lumboinguinal branch. I thought it was the Genitofemoral nerve because the genital branch passes through the deep inguinal ring, enters the inguinal canal, goes to spermatic cord and supplies the cremaster and scrotal skin.

Heres the image: https://upload.wikimedia.org/wikipedia/commons/e/e4/Gray824.png

Correct me if I am wrong please.

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gh889 I think you're right, FA2019 pp444 even states that sensory to the scrotum is via the Genitofemoral nerve +5

+2 upvote downvote
submitted by ∗mattnatomy(46)

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I believe they're referring to compression of branches of the Ilioinguinal Nerve (possibly the Anterior Scrotal Nerves.

Source: https://en.wikipedia.org/wiki/Anterior_scrotal_nerves

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armymed88 Ilioingual covers part of the medial thigh, base of penis and anterior scrotum Posterior scrotal nerves are a branch of pudendal and cover said area Doral nerves cover the dorsum of the penis which are also from the pudendal +1

meningitis I thought it was the Genitofemoral nerve because the genital branch supplies the cremaster and scrotal skin, but I looked it up and: The genital branch passes through the *deep inguinal ring* and enters the inguinal canal; also, Ilioinguinal wraps around the spermatic cord just like the question stem says. +2

jean_young2019 "The structures which pass through the canals differ between males and females: in males: the spermatic cord[6] and its coverings + the ilioinguinal nerve." from wiki "Inguinal canal", which means the ilioinguinal nerve lies on the external surface of spermatic cord. https://en.wikipedia.org/wiki/Inguinal_canal The contents of spermatic cord includes, "nerve to cremaster (genital branch of the genitofemoral nerve) and testicular nerves (sympathetic nerves). It is worth noting that the ilio-inguinal nerve is not actually located inside the spermatic cord, but runs along the outside of it, in the inguinal canal." from wiki spermatic cord. https://en.wikipedia.org/wiki/Spermatic_cord +1

kavarthapuanusha Lol idk all of these but, only thing i thought was spermatic cord torsion means loss of cremasteric reflex --> genitofemoral --> scrotum. Idk the rest of the options lol +

+2 upvote downvote
submitted by saifshaikh(13)

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I think this picture explains it well:

http://www.groinpainclinic.co.uk/data/images/nervesaffected.jpg

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hello Adding to this... The Q is describing the GENIOFEMORAL nerve, which runs EXTERNAL TO of spermatic cord at the superficial inguinal ring This Q is NOT referring to ilioinguinal nerve, which exits THROUGH the superficial inguinal canal +1

+2 upvote downvote
submitted by ∗diabetes(31)

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The pampiniform plexus, testicular artery, cremasteric artery, artery of the ductus deferens, lymphatic vessels, testicular sympathetic nerves, and ductus deferens all run deep to the internal spermatic fascia. The ilioinguinal nerve runs on the superficial surface of the external spermatic fascia The ilioinguinal nerve is a sensory nerve that innervates the skin over the groin region, the medial aspect of the thigh, the upper part of the scrotum and the penile root. It is normally encountered during open repair of inguinal hernia.

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+2 upvote downvote
submitted by ∗rainlad(33)

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The other answer choices:

motor innervation to the bulbocavernosus muscle = deep/muscular branch of the perineal nerve, which is branch of the pudendal nerve

motor innervation to the lower portion of the rectus abdominis muscle = thoraco-abdominal nerves, which are continuations of the T7-T11 intercostal nerves

sensation from the dorsal surface of the penis = dorsal nerve of the penis, which is the deepest division of the pudendal nerve

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+2 upvote downvote
submitted by skuutnasty(8)

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after rabbit-holing this one for a bit.... this is the photo that demonstrates it best (to me, anyway). must be ilioinguinal n.

enjoy

https://d1yboe6750e2cu.cloudfront.net/i/5e43dd40330f1cd702313cf56b29b8b3f793b00b

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drjo Ilioinguinal n. derived from L1 is mostly sensory supplying skin of upper and medial thigh root of penis & upper scrotum (males) **mons pubis & labia majora (females) it accompanies spermatic cord through superficial inguinal ring, great pic of this ^ @skuutnasty +

ankigravity Why is this not at the top.. It's the best image by far. +

+2 upvote downvote
submitted by ∗kevin(52)

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Just to clarify all the comments.

(B) Rectus innervation would not be as deep as the spermatic cord (thoracoabdominal/intercostal nerves)
(A) & (D) are both pudendal nerve, I think it's reasonable to exclude both as an answer choice as such
(C) Process of elimination. Sure, we can nitpick if it's genitofemoral or ilioinguinal but I think that's all we're being tested on here

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+1 upvote downvote
submitted by amd(1)

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It is the ILIOINGUINALguys stop misleading ppl! https://www.openanesthesia.org/aba_ilioinguinal_anatomy/

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+0 upvote downvote
submitted by ∗weirdmed51(30)

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The question states compressing a nerve on the external surface of spermatic cord. Genitofemoral nerve is within spermatic cord, not external to it. Hence it is ilioinguinal nerve which supplies anterior surface of scrotum. If still in doubt, doesn’t matter , bc genitofemoral n also supplies the anterior surface. chill y’all

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+0 upvote downvote
submitted by ∗mrizzle(0)

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This book chapter describes this stuff well if you can access it through the library.

Regional Nerve Blocks in Anesthesia and Pain Therapy Traditional and Ultrasound-Guided Techniques pg.707

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-1 upvote downvote
submitted by lisa(0)

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The question asks about a nerve that is on the EXTERNAL surface of the espermatic cord at the level of superficial ring, that is the ilioinguinal nerve, because the genital branch of the genitofemoral nerve goes inside.

The trick is that the genitofemoral is responsible of invervating the anterior surface of the escrotum, but the genital branch of the inguinal nerve that goes external is responsible of the superior anterior surface of the scrotum

Here you can see both nerves outside and inside the spermatic cord https://image.slidesharecdn.com/herniasdepared-170305224216/95/hernias-de-pared-10-638.jpg?cb=1488753771 and here you can see the inervation from both nerves https://medicalfoster.com/wp-content/uploads/2017/01/attelu-rezultati-vaicajumam-genitofemoral-nerve.jpeg

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kcyanide101 I got this off UWORLD: Ilioinguinal nerve is injured during hernia surgery. Pain to the base of the penis, anterior scrotum and labia Obturator usually injury during bladder surgery. Loss of addiction and pain to medial thigh. Genito femoral supplies similar areas as the ilio inguinal, you distingish it from the ilioinguinal ue to the loss of the cremasteric reflex. +

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