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+--- Thread: cn iv - step1saga (/showthread.php?tid=597770)
cn iv - step1saga - ArchivalUser - 07-09-2011
Can someone please explain what this means- this was in the errata in FA
If the
lesion is at the nucleus or occurs before the nerve crosses midline, the
head tilt will be toward the side of the lesion.
If the lesion occurs after the nerve crosses midline, the head tilts away from the lesion.
Note that
the lesion results in an eye going up and out, so on testing, the head will
tilt to try to align with the good eye
Thanks
0 - ArchivalUser - 07-09-2011
Hi
http://upload.wikimedia.org/wikipedia/en/1/14/Brainstem_trochlear.png
CN IV Nuclei supply the "Contralateral side"
(while other CN nuclei supply "Ipsilateral" with the exception of CN II)
i think u can figure it out now.
0 - ArchivalUser - 07-09-2011
one thing i wanted to add is that:
In either case "The Head will tilt to the Opposite side of the "Affected EYE"
(not talking about LESION site here)
0 - ArchivalUser - 07-09-2011
Oh I see so by midline thy mean after decussation and since nucleus is on midbrain
So on 4 it's the opposite of what is in 11 in which head can tilt toward lesion but defect in away from lesion
Hypoglosus also toward lesion
Thanks a lot sarim
0 - ArchivalUser - 07-09-2011
Why doesnt cn 2 affect ipsi after decussion? I know that t is a Cns nerve but it probably doesn't decussate? I mean it's def not on pons medulla and midbrain
0 - ArchivalUser - 07-09-2011
I mean cn 2 def affects ipsi and so no afferent light so no consensus reflex and no pupil conteaction by both eyes so cn 2 affects bilaterally ?