DrVirgo
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8a- A patient experiences difficulty in walking down stairs and reports some double vision as well. Which of the following is the most likely locus of the lesion?
A. Medulla
B. Dorsal pons
C. Ventromedial pons
D. Midbrain
E. Spinal cord
8b- The lesion most likely involved which of the following?
A. Cervical spinal cord ventral horn cells
B. Cranial nerve VII
C. Cranial nerve VI
D. Cranial nerve IV
E. Cranial nerve III
Explain the answer. thanks.
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| Natasa
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It should be n.trochlearis-IV cranial nerve,innervating superior oblique muscle.Usually,lesions produce diplopia and difficulties when walking down the stairs(superior obliquus moves eyeball down and lateraly).Nucleus is at the level of colliculus inferiorior in the midbrain.
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| reet
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good question...
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| DrVirgo
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ITs D and D.
Trochlear nerve lesion produces those symptoms and it comes out from the post part of the midbrain... I think its the only CN that comes out from the posterior side... can someone please confirm? or correct me if i'm wrong.
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| robin082006
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| ureterpolyp
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I think its the only CN that comes out from the posterior side... can someone please confirm? or correct me if i'm wrong.
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that's right, "dorsal"
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| DrVirgo
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Thanks everyone.
I think its important to know:
Lesion that makes eyeball look DOWN and OUT is: CN III Pasy.
Lesion that makes eyeball look DOWN and IN is: CN IV Palsy.
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| nadiabarati
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Natasa, superior oblique muscle moves eye down and inward, medially not laterally. I think you made a typing error
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| Geroo
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no superior oblique moves the eye down and out
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| sarika
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yes it is down and out (intortion)
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| nadiabarati
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hey! I'm confused! intortion means out???
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| nadiabarati
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muscle movements
A given extraocular muscle moves an eye in a specific manner, as follows: - medial rectus (MR)—moves the eye toward the nose lateral rectus (LR)—moves the eye away from the nose superior rectus (SR)—primarily moves the eye upward and secondarily rotates the top of the eye toward the nose inferior rectus (IR)—primarily moves the eye downward and secondarily rotates the top of the eye away from the nose superior oblique (SO)—primarily rotates the top of the eye toward the nose and secondarily moves the eye downward inferior oblique (IO)—primarily rotates the top of the eye away from the nose and secondarily moves the eye upward
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| DrVirgo
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Eye Movements:
SR: up and in
IR: down and in
SO: down and out
IO: up and out
SO and SR: intort (rotate the eye medially)
IO and IR: extort (rotate the eye laterally)
Edited by DrVirgo on 02/13/06 - 10:17 PM
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| DrVirgo
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How do I attach a pic? does it have to be only from the internet?
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| DrVirgo
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Great site to simulate eye movements and test yourself on lesions!
http://cim.ucdavis.edu/eyes/version1/eyesim.htm
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| msyamp
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hey . intorsion means twisting of e eye ball in AP axis like bringing 12 o clock postion point to 3 o clock.
if we look straight SOblique causes depression, intorsion and medil or inward look
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| DrVirgo
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msyamp: This is what I meant... am i right?:
SO and SR: intort (rotate the eye medially) e.g. -right eye rotates inward 12 to 3 oclock
IO and IR: extort (rotate the eye laterally) e.g. -right eye rotates outward 12 to 9 oclock
Edited by DrVirgo on 02/13/06 - 10:16 PM
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| msyamp
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no virgo SR and IO for elevation and IR and SO for depression.
the thing is all the muscles except obliques act on the eye ball from the medial side
because the optic ring attachment of mucles is placed so. there is no problem with medial and lateral recti.
http://images.encarta.msn.com/xrefmedia/aencmed/t...
  Figure 3. Diagram of the left superior rectus (SR) muscle. Figure 4. Diagram of the left superior oblique (SO) muscle (the superior rectus and levator muscles removed).  Figure 5. Diagram of the Tenon's capsule pulleys for the horizontal rectus muscles.
the superior and inferior rectus is they will do only elevation when eye is in abduction.that is when the axis of the muscle and axis of the eye are on same line.
if the eye is looking straight.
superior rectus causes elevation, adduction and intorsion,
inf oblique causes elevation, abduction and extorsion.both are elevation
inferior rectus causes depression, adduction and extorsion
suprior oblique causes depression, abduction, and intorsion.
please go through the diagram. you can understand.see any pcitures in greys or so to get a picture. or just memorise the above actions.
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| DrVirgo
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thats a good pic. thanks msyamp.
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