Thread: Neuroanatomy Q1*

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

may be the answer is A?

I think the correct answer is D.

From the question:

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

If we analyze quickly the answers...

Option B) Frontal Eye Field; is located in the posterior part of the middle frontal gyrus (Brodmann's area 8. It regulates voluntary contralateral horizontal gaze. A lesion here would give us Ipsilateral conjugate deviation of the eyes. (away from the lesion)

The left options C) Lateral Geniculate Nucleus; D) Optic tract and E) Visual cortex (Brodmann's area 17); would give us a contralateral component or other clinical features not present on this patient.



Therefore having only myosis on this pt we could think about another known condition called Horner's Syndrome which in this case could explain the clinic signs of the patient and give us so for the answer A) as we know Horner syndrome is due to paralysis of the cervical sympathetic nerves.

The symptoms of Horner's syndrome include:

* Drooping of the upper eyelid
* Swelling of the lower eyelid
* Sinking of the eyeball
* An absence of sweat on the same side of the face as the affected eye
* The pupil becomes smaller (miotic)
* Each iris may be a different color

Thanks Good Explanation

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definitely a horner's. A

The answer is A!!

The answer is A. and the explanation is quite good....