NB F2 S4 Right Small Pupil

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NB F2 S4 Right Small Pupil

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8 Posts

nadiabarati

06/07/06 - 07:43 AM

35. A 48-year-old man comes to his physician because his wife noticed that his right pupil is "small." Physical examination shows that the right pupil is constricted and does not react to light. His left pupil is normal. These findings are most likely due to a lesion involving which of the following structures on the right? A) Cervical spinal cord B) Frontal eye fields C) Lateral geniculate nucleus D) Optic tract E) Visual cortex

nadiabarati

06/07/06 - 07:44 AM

Everybody says horner,A

But why not D?! because optic tract plays a role in light reflex.

Light reflex should be present in Horner.

Please help me to get this...

robin082006
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06/07/06 - 08:35 AM

right optic tract--->no light reflex in both eyes when shining to right eye, Both eyes contrict when shining to left eye

right Horner's--> right eye contricts due to paralysis of right radial muscle--> no light reflex in right eye when shining to both eyes.

Edited by robin082006 on 06/07/06 - 09:46 AM

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nadiabarati

06/07/06 - 09:05 AM

the different muscles are involved. radia iris muscle is constricted and cause pupillary dilation by sympathetic fibers. sphincter iris muscle is constricted and cause pupillary constriction by parasympathetic fibers. So maybe it doesn't respond to light, because it's already constricted. Right?

Dr.Papez
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06/07/06 - 12:42 PM

not acceptable...A horner's pupil will respond to light reflex but less briskly.
The question is not properly framed: Ignore it and learn the concepts.

Causes for Miosis of one, but not the other
Iritis
Cervical sympathetic paralysis
Miotic drug (e.g. Pilocarpine)

study_ing
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06/07/06 - 01:59 PM

agreed. besides a unilateral lesion of the afferent pathway does not cause anisocoria (unequal pupils) because the consensual response in the normal eye is still fuctional.

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Cedrick
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07/11/06 - 02:12 PM

Dr.Papez wrote:
not acceptable...A horner's pupil will respond to light reflex but less briskly.
The question is not properly framed: Ignore it and learn the concepts.

Causes for Miosis of one, but not the other
Iritis
Cervical sympathetic paralysis
Miotic drug (e.g. Pilocarpine)

Ok Now that is better

docarchana
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09/10/06 - 06:08 PM

thanx papez for the info.

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