So, I am slightly confused because with the things I've been reading- whats being said is a bit of a contrast? In bradley's clincial neurology- they are saying that for upwards movements the axons cross over in the CN3 nucleus and not the PC and it is bilateral whereas for downwards movements the axons project only to ipsilateral CN4 and CN3 and the only time where the PC is being used is when fibres from the INC are decussating over for neural integration. Id really appreciate it is this was cleared for me! But otherwise Dr Lee is fabulous
I have read much the same. I also wish to ask is the innervation from the frontal eye fields for saccades bilateral or will it lateralise to one of the frontal eye fields and the other isn't involved in vertical saccades? I found the answer in another of your videos so its all good. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-iNYRPcrwJXw.html
In regards to upward vertical saccadic movement, this is primarily done by the riMLF, which gives bilateral innervation to elevator motoneurons, but unilateral innervation to depressor motoneurons. The bilateral innervations that the riMLF gives to elevator motoneurons does not cross in the PC. This is different to upward pursuit and gaze holding movement, which is done by the INC. This does cross in the PC, with upward fibres being more posterior than downward fibres. This is the issue with PSP and related disorders which affect the INC connections in the PC, but not necessarily the riMLF connections. Hope this helps.
The gaze centers are THE nuclei and Frontal Eye Fields in the cortex are Supranuclear. Watch this: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-K_5W83gwC-8.html
Yes, gaze centers are supranuclear up until just prior to synapsing with the nuclei of the brainstem gaze centers. From here, the brainstem gaze centers pathways get called infranuclear. Doll's eye maneuvers are VOR (vestibular ocular reflexes) that can directly order the brainstem gaze centers to power gaze, thus not needing at all the cortex gaze centers. So if the eyes move by turning the head, it proves the brainstem and distally gaze centers pathways are healthy. If the eyes do not move with head turning, you locate the pathology to the brainstem and distally. What if the supranuclear, nuclear, and infranuclear don't work, well, that's a coma that ominously includes a structural brainstem dysfunction, or less ominously, a coma of only metabolic/toxic cause we hope abates.
What nuclei in the cerebellum are involved in overshoot (failing to catch) the vertical saccades? Is it still fastigial n.? I have patients w good horizontal saccades (no over/under), but vertical accuracy is poor?
Hi alexander, according to Adam e Victor's Pirinciples of Neurology "The MLF is the main conduit of signals that control vertical gaze from the vestibular nuclei in the medulla to the midbrain centers. For this reason, with internuclear ophthalmoplegia, along with the characteristic adductor paresis on the affected side, vertical pursuit and the VOR are impaired" And we now that Flocculus/paraflocculus send modulatory eferences to the vestibular nuclei, to modulate saccadic pursuits.
The Gaze Centers are not supranuclear. They are THE nuclei and Doll's Eye Maneuver can move the eyes if the lesion is just supranuclear and not nuclear or infranuclear. Watch this and thank me later: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-K_5W83gwC-8.html
