 So I think we split this up so that I'm talking about the most afferent pathways and then we're going to efferent pathways and then Reese is going to talk about like inter-muscular issues. So I'm talking about super nuclear, nuclear and inter-nuclear causes of dystopia. So just kind of to be aware super nuclear processes mostly involve binocular processes such as pursuit, saccades, VOR, gaze-holding, fixation and optic connect nystagmus. Really the only non-binocular processes, virgins, that these super nuclear processes are most responsible for. So some causes of dystopia that are super nuclear are rare but these are the ones that are known, skew deviation, ocular tilt reaction, alternating skew, convergence, insufficiency, divergence, insufficiency and thalamic isodiguation which some of these kind of fit in with each other. So skew deviation, it's defined as a vertical misalignment secondary to damage along the oedolithic input to vertically acting ocular motor neurons. This is acquired, it's usually comatent but can be incometent and just so everyone knows, comatent means that it's the same amount in every gaze and incometent is when it changes. It can be central, peripheral, central is much more common and peripheral is usually caused by damage to the utricle, saccule or fibers along the brain on their feet. So ocular tilt reaction is a subtype of skew deviation. The triad includes a comatent skew deviation, head tilts and ocular torsion and the torsion is in the same direction as the head tilt. So for example, this is, there's actually a really good case on Iowa Irons if anyone's interested but this shows that if the lesion is basically from anywhere on the right side from the utricle, saccule up to the pons it will cause an ipsolateral head tilt. So here there's a right head tilt and then you can see on the fundus photographs that there's x-cyclotourism of the right eye and encyclotourism of the left eye. So alternating skew deviation is incometent and causes a hypertropia of the abducting eye. So there's a right hypertropion, right gaze that switches to a left hypertropion, left gaze. And the lesion is usually in the cerebellum cervical medullary junction or dorsal midbrain. So convergence and sufficiency is usually caused by dyplopia at near, it's usually benign finding and does not require further workup, but it can manifest with extra permedal disorders such as Parkinson's or PSP. So like usually you don't need to workup because it's often associated with these other symptoms. And then really the same thing with divergence and sufficiency, it's acquired and produces a cometant esodibiation that's greater at distance and near. It's also again benign if it's found in isolation but it's usually associated with other neurological symptoms if it's associated with a midbrain tumor or these spinal, it's a cerebellar otaxica. Convergence spasm, so in older patients it's almost never related to organic disease. Again, it can be associated with a dorsal midbrain syndrome and when acquired can be associated with lower brainstem and cerebellar insults. So thalamic esodibiation is just something that I think we need to know for board so it's usually associated with a thalamic hemorrhage and causes a horizontal strypismus. So nuclear third, it's extremely rare and it's composed of bilateral ptosis. It's a decentral caudal nucleus of three which innervates both levators and then you'll get a contralateral superior rectus palsy because each superior rectus is innervated by the contralateral cranial nerve three nucleus and then you'll obviously have the ebsolateral medial rectus inferior rectus and inferior oblique palsy. So really the nuclear fourth and sixth are exceedingly rare, almost never happen and they're kind of, they're basically associated with fasciculars syndrome which Conradie will be talking about but one thing to know about nuclear fourth is that the fibers cross so basically a right nuclear fourth causes a left fourth palsy and this is almost this again almost never occurs and Conradie will talk about the syndromes with the sixth. So inter nuclear lesions, so these are lesions along the medial longitudinal fasciculus and this is a pathway that connects the sixth nerve nucleus on one side with the medial rectus sub nucleus of the third nerve on the contralateral side and so there's an INO and a one and a half syndrome and there's also a bilateral INO. So really, I mean in med school we basically learn that it's when there's no adduction but it's really defined by slowed adduction velocity with saccades in one eye because they may have full range of motion so that's important to remember and they will have gaze evoked nystagmus in the AB ducting eye. They may have a simultaneous skewed at deviation, convergence may or may not be in text you can't use that most common causes are stroke and demyelination and then just make sure you think about myosthenia in these cases because that can mimic and myosthenia will usually not have the nystagmus in the AB ducting eye and myosthenia usually will have other associated symptoms. So this just kind of shows the pathway so in this case the so for lesion number one so that's this and this is from our ophthalmology review book just I kind of like to use the same pictures over and over again so that just sticks to my brain but so the lesion is right here with the left MLF and so if we're trying to look to the left the cranial nerve six a nucleus will fire and we'll get this lateral rectus to move over and simultaneously should send a signal over to the MLF over here that causes the sub nucleus of three to cause a medial rectus to move over to the left as well but if there's a lesion then that will happen and lesion number two is just showing if there's a bilateral I know which right here you can see that this patient is not able to adduct with either eye and here you can see that there's some basically edema here with the area where the MLF runs and then this is one and a half syndrome so basically that is when both the abducens nerve and the MLF are affected from a larger lesion so in this case here we have the left cranial nerve six firing so that fires just normally and then we try to go over to the MLF over here and that's not functioning if we want to look to the right the abducens nucleus is not is also affected so it can't move to the right and then the pathway over to the left MLF is also not working so you have complete paralysis and right gaze and you can see that with this patient because she can't look over to the right at all and she can only AB duct the left eye so my references and Connor I'll use that next