PCA Occlusion - Visual Field Defect ?

[Ludacris]

From the FA 2010 Errata, it says:

Pg 401: In the description for the posterior cerebral artery, please delete the word "homonymous"; a PCA defect affects only one side of the visual field.

I always throught it was Contralateral Homonymous Hemianopia w/ Macular Sparing, for example, A Right PCA stroke would cause a Left Homonymous Hemianopa w/ Macular Sparing... so both eyes would be affected - Left Eye: Temporal hemifield and Right Eye: Nasal hemifield.

On Pg 420 of FA 2010, Why is #3 Homonymous but #6 isn't Homonymous (according to their correction above)?

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[Day man]

From the FA 2010 Errata, it says:

Pg 401: In the description for the posterior cerebral artery, please delete the word “homonymous”; a PCA defect affects only one side of the visual field.

I always through it was Contralateral Homonymous Hemianopia w/ Macular Sparing, for example, A Right PCA stroke would cause a Left Homonymous Hemianopa w/ Macular Sparing... so both eyes would be affected - Left Eye: Temporal hemifield and Right Eye: Nasal hemifield.

On Pg 420 of FA 2010, Why is #3 Homonymous but #6 isn't Homonymous (according to their correction above)?

in 2011 they have what you wrote not the correction and I'm pretty sure you're thinking/rationale is correct (at least that's what i thought as well). i have no idea why they would put that in the errata, but apparently they made the same mistake in 2011?

 

[tco]

From the FA 2010 Errata, it says:

Pg 401: In the description for the posterior cerebral artery, please delete the word "homonymous"; a PCA defect affects only one side of the visual field.

I always through it was Contralateral Homonymous Hemianopia w/ Macular Sparing, for example, A Right PCA stroke would cause a Left Homonymous Hemianopa w/ Macular Sparing... so both eyes would be affected - Left Eye: Temporal hemifield and Right Eye: Nasal hemifield.

On Pg 420 of FA 2010, Why is #3 Homonymous but #6 isn't Homonymous (according to their correction above)?

According to Haines, you are correct and it both are homonymous. This makes sense, as "homonymous," basically means "having the same." Very interesting...

 

[Mellow Monster]

out of curiosity, what does "homonymous" refer to anyway? is it simply referring to having a visual defect in the same visual field (e.g. left) in both eyes?

 

[spyderracing32]

out of curiosity, what does "homonymous" refer to anyway? is it simply referring to having a visual defect in the same visual field (e.g. left) in both eyes?

This is what homonymous should be referring to. Whereas a pituitary tumor compressing the optic chiasm results in bilateral temporal heteronymous hemianopsia (where heteronymous means in two different visual fields). A blockage of the PCA should not result in a visual field defect one would refer to as homonymous due to the fact that it only causes a visual field defect in one eye.

 

[Mellow Monster]

This is what homonymous should be referring to. Whereas a pituitary tumor compressing the optic chiasm results in bilateral temporal heteronymous hemianopsia (where heteronymous means in two different visual fields). A blockage of the PCA should not result in a visual field defect one would refer to as homonymous due to the fact that it only causes a visual field defect in one eye.

hmm...is that right? My understanding is that an infarct of the PCA supplying the right occipital lobe will cause loss of vision in the left visual fields of both eyes (i.e. homonymous hemianopsia), with macular sparing. This is also what is shown in FA 2011...it just doesn't want to call it homonymous for some reason.

 

[tco]

hmm...is that right? My understanding is that an infarct of the PCA supplying the right occipital lobe will cause loss of vision in the left visual fields of both eyes (i.e. homonymous hemianopsia), with macular sparing. This is also what is shown in FA 2011...it just doesn't want to call it homonymous for some reason.

You're correct. For example, stroke of the left PCA would lead to right sided visual field loss with macular sparing. The macula has nerve fibers that project bilaterally.

 

[spyderracing32]

hmm...is that right? My understanding is that an infarct of the PCA supplying the right occipital lobe will cause loss of vision in the left visual fields of both eyes (i.e. homonymous hemianopsia), with macular sparing. This is also what is shown in FA 2011...it just doesn't want to call it homonymous for some reason.

Ugh, yea you're right. Unilateral visual field defects only occur in lesions pre-chiasm. Must be the pain-killers... my bad.

Edit: Re: the macular sparring, it's not due to the fact that the macula has nerve fibers that project bilaterally (it does, but that's not the point), it's due to the fact that MCA overlaps with the PCA at the occipital pole.

 

[snd5014]

From what I read they are not completely sure why macular sparring occurs. Literature lists both bilateral projections as well as the MCA PCA overlap at the occipital pole.

Walsh and Hoyt's clinical neuro-ophthalmology, pg 546/547 discusses such, google books should have it available.

 

[SlaveOfTCMC]

First Aid says the macula has its own blood supply (anterior choroidal artery)


MOreover, Kaplan also mentions "BINASAL hemianopsia" arising from an internal carotid artery deficit. However, it seems this would have to be a bilateral lesion then. Does anyone have more info on this?

 

[ThereHeIs]

First Aid says the macula has its own blood supply (anterior choroidal artery)


MOreover, Kaplan also mentions "BINASAL hemianopsia" arising from an internal carotid artery deficit. However, it seems this would have to be a bilateral lesion then. Does anyone have more info on this?

Bilateral internal carotid artery calcification can impinge the optic chiasm from both sides (High Yield Neuro 4th ed. pg 101)