Question about eye movement mechanisms not related to match

[buddy321]

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Hello,
I am working on a case study and I have a couple of questions that if someone could PLEASE help me out with I would greatly appreciate It;
1 If a patient has a very specific lesion in the brainstem- in just the PPRF( both nuclei) and the pretectal region of the midbrain- could that patient possibly have intact non conjugate eom on exam?
2 In terms of saccades and pursuit eye movements… when I test a patient’s eom and note that they are intact, could I also say that the patient’s saccades and pursuit eye movements are intact or can I only say that after performing oculocephalic reflex or vestibulo-ocular reflex (VOR)? And the other way around if a patient has vertical and horizontal gaze occular paresis on exam but has intact oculocphalic reflex… could I say that saccades and pursuit eye movements are intact?
Thank you very much in advance for your time.

 

[KHE]

Hello,
I am working on a case study and I have a couple of questions that if someone could PLEASE help me out with I would greatly appreciate It;
1 If a patient has a very specific lesion in the brainstem- in just the PPRF( both nuclei) and the pretectal region of the midbrain- could that patient possibly have intact non conjugate eom on exam?
2 In terms of saccades and pursuit eye movements… when I test a patient’s eom and note that they are intact, could I also say that the patient’s saccades and pursuit eye movements are intact or can I only say that after performing oculocephalic reflex or vestibulo-ocular reflex (VOR)? And the other way around if a patient has vertical and horizontal gaze occular paresis on exam but has intact oculocphalic reflex… could I say that saccades and pursuit eye movements are intact?
Thank you very much in advance for your time.

Holy crap! That almost made my head explode. But just because it's good to think about things like this sometime, I'm going to give it a shot based on memory so don't take this as gospel and others please feel free to correct here:

Question 1:

A lesion of both PPRFs and the pretectal region of the midbrain should, at least in theory, allow for intact non conjugate EOM movement on exam because CN nucleii III, IV, and VI would still be intact. The lesion of the pretectal region would result in a palsy of conjugate upgaze but should not in theory affect non conjugate EOM movement.

Question 2:

It doesn't seem to me that you would be able to say anything regarding pursuit or saccadic eye movements based on EOMs.

If you do EOM testing with both eyes open that is itself a test of pursuits, so you would right off the bat not be able to say anything about saccadic function. If you do EOM testing with one eye covered, you aren't testing true pursuits or saccadic movement which I think almost by definition require binocular fixation.

The VOR response seems irrelevant with respect to pursuits and saccades because the movements associated with a VOR response come from a different supranuclear center than do voluntary pursuits and saccadic movements.

The question almost seems to answer itself. If a patient has both horizontal and vertical gaze pareisis, how are they going to generate a saccade?


God....I think I have some neural damage myself.

Others, please chime in.