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  #1  
Old 01-09-2014
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Default question neuro

HEy guys, What does "non pupil sparing" palsy mean (it arises from CN 3 aneyursm vs an aneyursm of Basilar artery would not cause that. Its from a uworld concept. Please help thank you
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Old 01-09-2014
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If ive understood your question correctly:

Cranial nerve III has 2 "components" - a motor component which supplies motor innervation to the extraocular muscles, and a parasympathetic component which supplies the pupil constrictor muscle

The motor component is in the middle of the nerve, and the parasympathetic component is on the outside of the nerve (remember this by "motor in the middle, parasympathetic on the periphery")

A palsy of CNIII can therefore affect either or both of these components.

A pupil sparing palsy affects the central motor component only, causing weakness of the extraocular muscles (the "down and out" position) but preservation of the parasympathetic pupil constricting action on shining a light in the eye, and is caused by something reducing the diffusion of oxygen etc to the centre of the nerve, eg diabetic vascular disease

A non-pupil sparing palsy affects both the middle motor component and peripheral parasympathetic component - producing a dilated "blown" pupil, and then weakness of the extraocular muscles - in that order. Its caused by a mass compressing the nerve from the outside, eg an aneurysm or a herniating uncus or something equally nasty.
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  #3  
Old 01-10-2014
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Default Thanks!

Quote:
Originally Posted by USMLEUK. View Post
If ive understood your question correctly:

Cranial nerve III has 2 "components" - a motor component which supplies motor innervation to the extraocular muscles, and a parasympathetic component which supplies the pupil constrictor muscle

The motor component is in the middle of the nerve, and the parasympathetic component is on the outside of the nerve (remember this by "motor in the middle, parasympathetic on the periphery")

A palsy of CNIII can therefore affect either or both of these components.

A pupil sparing palsy affects the central motor component only, causing weakness of the extraocular muscles (the "down and out" position) but preservation of the parasympathetic pupil constricting action on shining a light in the eye, and is caused by something reducing the diffusion of oxygen etc to the centre of the nerve, eg diabetic vascular disease

A non-pupil sparing palsy affects both the middle motor component and peripheral parasympathetic component - producing a dilated "blown" pupil, and then weakness of the extraocular muscles - in that order. Its caused by a mass compressing the nerve from the outside, eg an aneurysm or a herniating uncus or something equally nasty.
Thank you that was super helpful . god bless
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  #4  
Old 01-10-2014
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Quote:
Originally Posted by USMLEUK. View Post
If ive understood your question correctly:

Cranial nerve III has 2 "components" - a motor component which supplies motor innervation to the extraocular muscles, and a parasympathetic component which supplies the pupil constrictor muscle

The motor component is in the middle of the nerve, and the parasympathetic component is on the outside of the nerve (remember this by "motor in the middle, parasympathetic on the periphery")

A palsy of CNIII can therefore affect either or both of these components.

A pupil sparing palsy affects the central motor component only, causing weakness of the extraocular muscles (the "down and out" position) but preservation of the parasympathetic pupil constricting action on shining a light in the eye, and is caused by something reducing the diffusion of oxygen etc to the centre of the nerve, eg diabetic vascular disease

A non-pupil sparing palsy affects both the middle motor component and peripheral parasympathetic component - producing a dilated "blown" pupil, and then weakness of the extraocular muscles - in that order. Its caused by a mass compressing the nerve from the outside, eg an aneurysm or a herniating uncus or something equally nasty.
wow i didnt even pick up on the location of the motor and parasympathetic fibers in CN III during my studies! .
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  #5  
Old 01-10-2014
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Quote:
Originally Posted by CisternaChyli View Post
wow i didnt even pick up on the location of the motor and parasympathetic fibers in CN III during my studies! .
Yea I also just learnt it from his superp explanation.
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  #6  
Old 01-11-2014
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Default Neuro q 2

Hey guys! I have another neuro q.. in USMLE RX it says where is dopamine producded from and I picked nigrostrial pathway but the answer is PUtamen. DOes anyone know why? I can give more information if need be from that question. appreciate it
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