Jackofknives
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An active mountain climber develops pain in the buttock and tingling and numbness in the lower limb as a result of hypertrophy of the piriformis muscle. Which region of the lower limb is most likelyto be a site of the altered sensation?
(A) Posterior thigh
(B) Lateralleg
(C) Medial thigh
(D) Sole of the foot
(E) Gluteal region
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A football player has suffered severe trauma to the lateral part of the left leg just below the knee. He drags his left toe when he walks and cannot feel the dorsum of the foot. Which of the following will still be intact?
(A) Dorsiflexion
(B) Inversion
(C) Eversion
(D) Cutaneous sensation of the medial leg
(E) Cutaneous sensation between the great toe and the second toe
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| monam84
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1- Sounds like the sciatic nerve or inferior gluteal nerve (most likely the sciatic) so in that case in narrows it down to (A), (D), or (E). And just purely speculation the posterior thigh would proly be the most likely location
Answer- (A)
The reason I chose sciatic instead of say inferior gluteal would be that the q asks for a change in sensation in the lower limb.
2- I had it down to B and D, Im pretty sure the cutaneous sensation on ledial leg is from tibial nerve. So that leaves me with
Answer: (B)
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| forumdoctor
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E . Gluteal region
D. Cutaneous region of medial of the leg.
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| hedieh
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After a review on anatomy:
The best answer 4 first question is A. Because ventarl rami of S2 S3 & S1 pass across the piriformis muscle. These 3 nerves toghether, form the posterior cutaneus nerve of tigh, which provides sesation of posterior tigh.
second question:
Injury to common proneal nerve:
Inability to dorsiflexion and evertion. The answer is:B
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| forumdoctor
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jack answer plsssssssssssssssssssssssssssssssss
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| Jackofknives
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I'm mad at these questions b/c they are flawed.
First question:
Piriformis hypertrophy will ALWAYS clamp SCIATIC nerve. Always! Not posterior cutanous nerve. No comes the flawed part, the sources says it’s (B), which is correct. But clamping of sciatic nerve will and could affect both tibial and common peroneal nerve, so option B and D are equally good.
Second question:
Tibial nerve is intact. Now comes the flawed part, source says D is correct, fair enough. BUT (B) is also correct b/c triceps surae is THE most powerful inversion muscle, and all inversion muscles are innervated by tibial nerve.
To summarize:
Correct answer by source:
1. B
2. D
Other correct options:
1. D
2. B
I hope USMLE doesn’t make this kind of mistakes.
P.S. these questions are from Kaplan anatomy review book, 2004 edition.
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| forumdoctor
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jack, Deep peroneal function: weekened inversion, loss of extension of the digits, loss of dorsiflexion (foot drop) sensory loss on the antero lateral of the leg.
superficial nerve: loss of eversion of the foot. sensory loss on dorsum of the foot except the first web space.
since deep peroneal nerve have weekened inversion function, u can eliminate that option.
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| forumdoctor
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jack can u explain the first one.
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| Jackofknives
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That cannot be true, I've drawn the inversion/eversion axis of subtalaris joint and the insertion, the 4 main inversion muscles that have can invert the foot. Namely Achilis tendo, flexor hallucis longus, flexor digitorum longus, tibialis posterior – all innervated by tibial nerve.
It’s in my text book aswell. I’m using a Danish one.
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| Jackofknives
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If you have seen the projection of the nerves of sacral plexus on real bodies it is clear the piriformis muscle will clamp sciatic nerve.
Posteior thigh is innervated by cutanous femoris nerve.
Lateral leg is innervated by cutanous sural lateralis, from peroneal superficialis
Medial thigh is a combination of sephanous nerve, pars femoralis from iliofemoralis (upper thigh), n. obturatorius.
Glutial region is from the clunious nerves, upper, medial and lower. They are not from plexus lumbal sacralis except the lower, which is a part of n. cutaneus perforans from S2,3,4, part of plexus sacralis.
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| forumdoctor
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jack my source is kaplan 2001 edition, page number 218.
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| monam84
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wow, that was tricky
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| forumdoctor
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Thanks jack for explanation.
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| Jackofknives
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Heck I was uncareful forumdoc, you are right. Tibialis anterior is inverter, too.
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