Full transcript
0:07all Ninja nerds in this video we're
0:08going to talk about the third cranial
0:10nerve or the ocular motor nerve so what
0:12we're going to discuss in this video is
0:13we're going to talk about the origin of
0:14the nerve where you can actually find
0:15the nucleus of this Nerf what structures
0:17are surrounding it within the brain stem
0:20course of the Nerf so we're going to
0:21talk about what structures that actually
0:22might pass by certain vessels certain
0:24Dural sinuses certain holes within the
0:26skull and then we'll talk about the many
0:28structures that it's supplying and the
0:29functions of those structures and then
0:31we'll finish off with a little bit of
0:32tidbit on clinical correlation
0:34specifically about Weber and Benedict
0:36syndrome and then some other certain
0:38situations too all right so let's go
0:39ahead and get started so first off where
0:41can we find the third cranial nerve well
0:44before we actually look at it in this
0:45large structure here I want to take a
0:47look at it from the anterior view so I
0:49want to imagine that you guys are
0:50looking at me you guys are looking at my
0:51brain stem this is exactly how we're
0:54going to see it so we're seeing here the
0:56anterior view of the brain stem and I'm
0:57taking a slice an actual section of the
1:00midbrain we're looking at it from the
1:01top all right so this right here is
1:03midbrain now here you have a tiny little
1:06Canal it's a little cerebral spinal
1:08fluid uh containing Canal right here in
1:10the center that structure there is
1:12called the cerebral Aqueduct okay so
1:14it's actually superiorly connected with
1:15a third ventricle inferiorly connected
1:17with the fourth ventricle surrounding it
1:20this uh reddish color here is going to
1:22be What's called the per aqueductal gray
1:24matter okay so it's very important for
1:26certain autonomic functionings right so
1:28again this is the periductal gray matter
1:30matter on the sides of it on the sides
1:33of it is actually going to be the
1:35nucleus of the third cranial nerve so
1:37right here you're going to see here the
1:40nucleus for the third cranial nerve now
1:44on the sides of it it's also going to
1:45have parasympathetic neurons so right
1:48here next to it I'm also going to have
1:50parasympathetic neurons let's draw these
1:52ones here in this blue color so these
1:55right here on the sides these are going
1:58to be the parasympathetic neurons that
2:00are moving with the ocul motor Nerf now
2:03they give a spe a special name to these
2:05nuclei right here this blue nuclei they
2:07call it the
2:10Edinger
2:13Westfall nucleus and the Edinger
2:16Westfall nucleus is the parasympathetic
2:19nervous system nucleus okay so it's
2:21containing parasympathetic fibers that
2:23are going to supply What's called the
2:25ciliaris and the iris and we'll talk
2:27about that okay now just a little bit of
2:29other neuro Anatomy here
2:32anterior to this we're going to have
2:34this kind of little special structure
2:36right
2:37here this structure here is consisting
2:40of
2:41descending corticospinal fibers so this
2:44is consisting of descending
2:45corticospinal fibers this is actually
2:47called the Crux
2:50cerebri and this is consisting of
2:52descending corticospinal
2:54fibers motor fibers now here on the
2:58sides over here on on the sides of the
3:00parasympathetic fibers of this
3:01parasympathetic nucleus right here
3:03there's going to be this green sets of
3:06fibers green sets of myelinated axons
3:09here and this is carrying up sensory
3:11information from proprio reception from
3:14touch fine discriminative touch maybe
3:16even a little bit of pressure this
3:17structure here is called the medial
3:20liscus and then same thing over here
3:22medial
3:23liscus now in the posterior part
3:27here in the posterior part back here
3:30there's going to be a special structure
3:32here that controls your reflexive eye
3:35movements with response to your visual
3:37stimulus your visual fields that
3:40structure right there in pink is
3:41actually called The Superior calculus so
3:45it's called The Superior calculus
3:46there's one below which is the inferior
3:48calculus which controls your reflex of
3:50eye and head movements with response to
3:52auditory
3:53stimulus okay so medial liscus here on
3:55the sides Crux cerebri with the
3:57descending cortical spinal fibers
3:59anterior to it and there's another
4:01structure which is just anterior to that
4:04let's do this one right
4:06here right here we're going to have
4:08another structure this actually be
4:11perfect if I would have drawn it red but
4:13whatever this right here is called the
4:15red nucleus okay this right here is
4:18called the red
4:20nucleus so that's the red nucleus and
4:22the red nucleus actually has descending
4:24fibers that actually do cross they're
4:26they provide contralateral fibers that
4:28go to the muscles for limb flexion most
4:31commonly distal L flexion all right so
4:33where do we find the actual third
4:35cranial nerve or the OC motor nerve
4:37posterior to it is going to be the
4:39superior calculus on the sides of it is
4:42the medial Lum miniscus anterior to it
4:44is the red nucleus and then interior to
4:46that is the Crux cerebri so this is
4:48exactly where we're going to find the
4:50third cranial nerve all right sweet so
4:53we see it in this View and then what's
4:55going to happen is these fibers are
4:58actually going to pass a little bit
5:00might pass through the actual red
5:03nucleus and then they'll move out
5:05through this little cerebral spinal
5:06fluid like field cavity here here in the
5:08center this is called the
5:09interpeduncular Fuca right here it's
5:11consisting of cerebral spinal fluid and
5:13again what fibers are going to be moving
5:15with it the parasympathetic fibers okay
5:18the parasympathetic fibers all right
5:20sweet so we know exactly how it's
5:22exiting from the actual brain stem or
5:25the central nervous system so let's go
5:26ahead and look at it now at this level
5:28so again what structure would we
5:30have back here we would have the
5:34superior calculus and then what would
5:36this one be this would be the inferior
5:38calculus the reason why I'm telling you
5:39this is because the third cranial nerve
5:41is found at the level of superior
5:43calculus the fourth is found at the
5:45level of inferior calculus okay so again
5:48which one was this this was the third
5:49cranial nerve but to be very very
5:52specific these fibers here that are
5:54coming out these black fibers these are
5:56your somat motor fibers or in
5:58specifically these are your I'm going to
6:01write it like this here these are my
6:04G fibers somatomotor fibers are General
6:07somatic eference they Supply some of the
6:10extraocular eye muscles the reason why
6:13I'm mentioning that is we said that
6:15there was parasympathetic fibers that
6:17move with
6:19it these fibers these neurons are
6:22actually going to be gve General
6:25visceral eant which are parasympathetic
6:28fibers okay okay now what structures it
6:31is actually passing by as it moves
6:33through a little bit of neuro Anatomy
6:35here nothing
6:37crazy there's actually some more
6:39structures here so you know you have
6:41What's called the vertebral arteries
6:42they come up through the transverse
6:43foramina within the cervical vertebrae
6:45as they come up they come together and
6:48form what's called this basill artery
6:50and then the basill artery actually
6:52comes out and gives off What's called
6:54the posterior cerebral arteries which
6:56become a part of The Circle of Willis
7:00also it gives off another Branch here
7:02which is called the superior cerebellar
7:05arteries so Superior cerebella arteries
7:08and then there's even more there's
7:09anterior inferior um anterior inferior
7:12cerebella arteries we're not going to go
7:14into all of this what I want you to know
7:17is the third cranial nerve is actually
7:20going to run under the posterior
7:24cerebral artery and above the superior C
7:30artery same thing with these
7:32parasympathetic fibers they're going to
7:34move under the posterior cerebra artery
7:38and above the superior cerebr artery all
7:41right so now that we know that what will
7:43we see right here what would be
7:46above this would be the posterior
7:48cerebral artery and Below would be the
7:51superior cerebella artery simple as that
7:56now where do these fibers go next this
7:59was the first place right so they go in
8:00between the posterior cerebral and
8:02Superior cerebella then from here
8:05there's this special Dural cus you know
8:08deral sinus you know there's what's
8:09actually called the Duram Mater actually
8:12before I well no we'll stay here for
8:14just a second there's two parts of the
8:16duramater one is called the periostial
8:18layer and one is called the menal layer
8:21you see this Green Layer right
8:23there this Green Layer right here is
8:26actually called the periostal
8:30layer of the duramater that's a nice
8:32green color there
8:35then this pink one right here this pink
8:38one right there is actually called the
8:42menal layer of the Duram Mater okay the
8:46meningi layer of the
8:47derod what happens is there's a dural
8:49sinus here you know you see how this
8:51meningi layer separates from the
8:52periostal layer just kind of has that
8:54little separation there and there's a
8:55blue structure right there this blue
8:57structure is a dural sinus and that
8:59Dural sinus is called the cavernous
9:04sinus it's called the cavernous sinus
9:07now another way to look at the cavern of
9:09sinus is to look at it from a different
9:11view so what I have up here is you're
9:13going to see what's called the Cela of
9:15this pheno bone that's where the
9:17pituitary gland sits not your testicles
9:19these are not testicles these are the
9:21pituitary gland so again this is the
9:22cell TSA this fenoy bone and then you're
9:24going to see over here you're going to
9:26see these little uh kind of like little
9:27indentations here where these blue
9:30structure is that's the cavernous sinus
9:32but you're looking at from like a
9:33posterior view what happens is there's
9:35an artery a very very important artery
9:39that runs up through this structure here
9:42and this is called the internal cored
9:44artery and again you'd have one here
9:47this would be the left you'd also have a
9:49internal cored artery coming over this
9:52way that's moving through the cavity so
9:54the internal corod arter is moving
9:56through the cavity of the cavernous
9:58sinus there's actually another nerve
10:00that's moving in this vicinity too it's
10:02called the sixth cranial nerve the Abdu
10:05nerve now the reason why I'm saying that
10:08is because the oculam motor nerve
10:10cranial nerve 3 runs within this lateral
10:13wall okay so it runs Within These
10:15lateral walls of the cavern of sinus and
10:18if you really want to know the fourth
10:20cranial nerve runs right underneath
10:22it and then there's actually another
10:25division which is called the uh
10:28Opthalmic division of the trial Nerf so
10:30the Opthalmic division runs right
10:32underneath it and then there's another
10:34one which is the maxillary division of
10:36the trial nerve and that runs right
10:39underneath it okay so where's the th
10:41cranial nerve actually running it's
10:43running within the lateral wall of the
10:44cavernous sinus and again just to be
10:47clear here this is called the foramin
10:50lerum this is called the
10:53foramin lerum and what happens is this
10:56internal cored artery actually comes
10:58from the CTIC canal and then moves
11:01upwards through the cavernous sinus so
11:06if you really wanted to know there would
11:07be another structure here another bony
11:09Canal that actually runs through right
11:10here and this bony Canal is actually
11:13called the karate
11:15Canal all right so where does this
11:17sucker move this third cranial nerve is
11:19moving through here it's moving within
11:20the lateral wall so pose is moving
11:22within the lateral wall and it's coming
11:24out here and again what fibers are
11:26moving with it the parasympathetic
11:28fibers
11:29the parasympathetic fibers moving with
11:31it and it moves through the cavern of
11:34sinus all right so it exits out or it
11:37comes out through this cavernous sinus
11:39okay these are the parasympathetic
11:41fibers and the somatomotor fibers so if
11:43you really want to be specific these are
11:45the gsse fibers in black and the blue
11:47are going to be the gve
11:49fibers okay so now what happens they
11:52move out of the cavern of sinus and then
11:55they go through a hole in the skull
11:58which is called called The Superior
12:00orbital Fisher so what is this hole
12:02right here
12:03called
12:06Superior
12:09orbital fish all right cool so now what
12:13happens is these samatam motor fibers
12:16and these parasympathetic fibers move
12:17through the superior orbital Fisher and
12:19into the actual back of the orbit but
12:22from this view it doesn't do a Justice
12:24how exactly it's actually moving through
12:26we'll go over and see it from another
12:28view in a second here
12:29what happens is once the actual ocular
12:32motor nerve moves through the superior
12:33orbital fissure it gives off two
12:35branches okay one is called a superior
12:39branch and the other one is called the
12:42inferior Branch okay now if you really
12:48want to know because I know you guys do
12:50the parasympathetic fibers particularly
12:52move with the inferior Branch they
12:54particularly move at the inferior branch
12:56and then what happens is these
12:57parasympathetic fibers come off the
12:59inferior branch and they go to a
13:02ganglia they go to a ganglia what what
13:05is the definition of a ganglia a ganglia
13:07is a group of cell bodies located within
13:08the peripheral nervous system so those
13:11cell bodies there are postganglionic
13:13parasympathetic motor neurons from here
13:15they're going to come out and they're
13:17going to go and Supply the iris
13:20specifically the sphincter pupila and
13:22they're going to supply the ciliaris
13:24muscle and cause the ciliaris muscle to
13:25contract which Alters the shape of the
13:27lens particularly making the the lens
13:29very globular okay and when you make the
13:33lens globular that's actually going to
13:34be for very close Vision okay or or near
13:37Vision if you will all right all right
13:41cool that's that part and again just
13:43again what is this ganglion here called
13:45This is called the
13:49ciliary gangon
13:52okay now what happens is the superior
13:55branch of the ocular motor nerve is
13:57actually going to supply mainly two
13:59different structures here we're going to
14:01see it better in another another view
14:02here in a second but look what happens
14:03here Superior Branch gives off fibers
14:05that Supply this muscle right here okay
14:09this muscle here is a really cool muscle
14:11it actually connects to should actually
14:14be very very particular here there's
14:16actually a structure here called the
14:17tarsal plate which has the tarso glands
14:20near it right so the tarso glands so
14:22right there is called the tarsal plate
14:24and what happens is this muscle connects
14:26to the tarso plate as well as with the
14:28orbicular oculi this right here this
14:31muscle here is called the
14:34levator
14:37palpa
14:39superioris okay elevates the upper palp
14:42or the superior palp the ocular motor
14:44nerve Superior Branch supplies that
14:46there's another muscle here you see this
14:48one right here this muscle here I'm
14:50going to denote it Sr
14:52for superior rectus the superior
14:56division also gives all fibers that
14:58supplies
14:59the superior rectus what is the function
15:02of the superior rectus it elevates the
15:04eyeball lifts it upwards right the
15:07inferior branch is going to
15:10supply a muscle right here and this
15:12muscle right here is called the inferior
15:15oblique I'm going to denot IO we'll see
15:18it again a little bit later here it's
15:20going to give off another branch which
15:21is going to supply this muscle here and
15:24this muscle I'm going to denote as i r
15:27inferior rectus
15:29and then there's another branch that you
15:31can't see here it would actually be here
15:33in the back we'll see it in a different
15:34view here in a second but it's going to
15:36go to another muscle called the medial
15:38rectus and we'll see that in a better
15:40view in just a second okay so Superior
15:45Branch goes to levor palp Superior Su
15:48and also goes to the superior rectus
15:50inferior Branch goes to the medial
15:51rectus inferior oblique and inferior
15:54rectus okay we'll highlight these
15:55functions in just a second but let's
15:57take two more views at the
15:59okay one is I want to get another look
16:01at the inferior oblique so this muscle
16:04up here we'll talk about this when we
16:05talk about the trar nerve this is
16:07actually called The
16:08Superior
16:10oblique this one down here is called the
16:14inferior oblique now if you look here
16:18the inferior oblique is actually coming
16:20from the medial side like the nasal side
16:23and coming underneath the eyeball and
16:25attaching to the inferior lateral
16:27portion of the eyeball and then and then
16:29when it contracts it does something
16:30really interesting it pulls from that
16:32portion and it pulls upwards and when it
16:36pulls it upwards it pulls the eyeball
16:38upwards and rotates it outward so it
16:42pulls it upwards so elevates the eyeball
16:44and it rotates the eyeball out laterally
16:47so it does what's called Superior and
16:48lateral rotation all right that's really
16:50cool with the inferior Bleak that's that
16:53view and again we'll talk about the
16:54superior Bleak with the trolear nerve a
16:56nice little acronym uh someone once told
16:58me was like this
17:00lr6 s
17:02so4 and a um all the rest
17:07atr3 okay lr6 means lateral rectus six
17:12cranial nerve Superior oblique fourth
17:15cranial nerve and all the rest third
17:18cranial nerve okay so it's just an easy
17:19way to remember which nerve supplies
17:21which muscle okay so that's that
17:24view now imagine I'm taking my eyeball
17:28and I'm trying to look
17:29look in the back of this this eyeball
17:32here I'm trying to look all the way in
17:34the back posterior part of the orbital
17:35cavity this is what I'm going to see and
17:38just to be really specific again this is
17:39the posterior wall of the orbital cavity
17:41this could be like the temporal side so
17:44the temple side and this over here would
17:46be towards the nasal side so where the
17:49the the Honker is right now what happens
17:52is and I'm going to mention the
17:54structure because it's important there's
17:56this blue ring here you see see this
17:58hole right here this this is just a
17:59superior orbital fisser so this hole
18:01right here is actually the
18:03superior orbital fisser so Superior
18:06orbital
18:07Fisher just looking at from the actual
18:10posterior part of the orbital cavity
18:12this right here is actually called the
18:14optic Canal this is where the second
18:17cranial nerve runs through the optic
18:18nerve along with the Opthalmic artery
18:21okay so here I'll put that in there for
18:22you
18:23too all right now this blue structure
18:26here is actually called the common
18:28tendonous ring or the annulus of Zen so
18:30they call this the annulus of
18:33Zen or the common tendonous ring why am
18:38I mentioning this because it acts as the
18:40origin for four extraocular eye muscles
18:43okay so it acts as the origin for which
18:46muscles superior
18:48rectus if this is nasal side this is
18:50medial so this is medial rectus this is
18:54the inferior rectus and this is the
18:57lateral rectus okay
18:59the common tendonous ring is the origin
19:01for these extraocular eye muscles also
19:03it separates this Superior orbital
19:05fissure into two compartments one with
19:07inside of the common tendonous ring and
19:10the parts which outside the common
19:12tendonous ring now the ocula motor nerve
19:15has that Superior
19:17Branch it's within the common tendonous
19:19ring the inferior branch is within the
19:22common tendonous ring and what else uh
19:25if you want to be really particular you
19:26know there's another nerve called the
19:28naso ilary nerve which is actually a
19:30branch off the Opthalmic division which
19:33is a branch of the trigeminal nerve
19:35that's called the nasociliary and then
19:37if you want to be even more great
19:39students out there you'll know that the
19:41sixth cranial
19:42nerve abducens runs right within the
19:45common tendonous ring also and then if
19:47you guys want to be great you can
19:49remember that there's actually going to
19:50be the lacrimal nerve frontal nerve and
19:53trolear nerve someone once told me liver
19:55function test lacrimal nerve frontal
19:58nerve and TR nerve or the fourth cranial
20:00nerve run within out the uh super
20:01orbital Fisher outside of the common
20:03tendonous ring okay all right now
20:07Superior Branch
20:08supplies this muscle here and supplies
20:11this muscle here I didn't hit this one
20:14this is just another view of the levator
20:16palpa superioris and this one over here
20:19is the superior Bleak so Superior Branch
20:22supplies superior rectus which elevates
20:24the eyeball and levator palpa superioris
20:26which elevates the upper eyelid inferior
20:29Branch supplies the medial rectus which
20:32causes adduction of the eyeball or
20:33medial rotation of the
20:35eyeball and IT Supplies the inferior
20:38rectus which actually depresses the
20:40eyeball and then it also supplies the
20:42inferior Bleak which actually elevates
20:44and laterally rotates the eyeball let's
20:46highlight these functions here so what
20:47is its functions so if we take here
20:50third cranial
20:53nerve
20:55okay has how many branches here it has a
20:58a superior
21:00Branch it has an inferior branch and if
21:03we really want to be particular we'll do
21:05it in the same color as that nerve it
21:08also is going to have those
21:10parasympathetic fibers so it's also
21:12going to have those parasympathetic
21:14nervous system
21:16fibers okay what was the function of
21:18those parasympathetic fibers they were
21:20to cause they were to affect the iris
21:23they control the pupil
21:26size okay specifically they go to What's
21:28called the sphincter pupila and cause it
21:30to constrict and it controls the
21:33ciliaris muscle okay which controls the
21:36lens specifically the accommodation of
21:39the lens which basically helps with near
21:42Vision Superior Branch
21:46supplies superior rectus and levator
21:51palra Superior what does the superior
21:54rectus do it basically elevates the
21:56eyeball lavador pap Superior does what
22:00elevates the upper eyelid and the
22:03inferior branch is going to be supplying
22:05the inferior oblique inferior rectus and
22:10medior rectus inferior oblique elevates
22:13the eyeball and rotates it laterally
22:15inferior rectus depresses the eyeball
22:17and rotates it IM medially medial rectus
22:20adducts the eyeball or medially rotates
22:21it and if you really want to remember
22:23superior rectus also does not only just
22:26elevation of the eyeball but it also can
22:28Med immediately rotate the eyeball all
22:30right that's the third
22:32nerve all right sweet
22:35deal something else I want to talk about
22:37with respect to these parasympathetic
22:39and samatam motor fibers to be really
22:41really particular they are running right
22:43next to each other but to even be very
22:45very very specific they're actually
22:46running in another way let me highlight
22:48it like
22:50this imagine here I have like a
22:54tube
22:55okay like this and then inside of the
22:59tube I'm going to have something
23:01else here all this stuff in
23:04Black look at this this is a beautiful
23:07design okay that black part is the gsse
23:10fibers okay the samatam motor fibers all
23:14this stuff around it in
23:16blue is going to be
23:18the parasympathetic fibers or the gve
23:22fibers why is that important because
23:26there are certain clinical correlations
23:27to this that we'll talk about in just a
23:29second as we go through all of them
23:31sequence by sequence or along the course
23:34of the nerve but again what are these
23:36blue fibers here they're the gve fibers
23:39they're the parasympathetic fibers so
23:41parasympathetic nervous system fibers
23:43and these ones over here the black ones
23:45are the
23:46somato motor fibers these are the ones
23:48that are going to the extraocular
23:50muscles the gve ones are the ones going
23:52into the ciliaris and the synr pupila
23:55this does have some clinical correlation
23:57to it one other thing thing is there's
24:00blood vessels that supply this you guys
24:02might remember this when we talked about
24:04it in the cardiovascular system uh there
24:06was What's called the Vasa vasorum it
24:08was basically the vessels that supplied
24:10vessels this is very similar except
24:14instead of it supplying
24:16vessels IT Supplies the nerves so they
24:20don't call the Vasa vorm they call it
24:23the Vasa
24:25nervosum okay so it's a tiny micro
24:27system of blood vessels
24:28that are specifically supplying the
24:31actual somat motor fibers what is this
24:33actual vascular system here called the
24:36Vasa
24:38nervosum so it's a beautiful thing that
24:41is supplying the actual primarily the
24:43amam motor fibers the microvessels that
24:45also has a little bit of Chlor chemical
24:46correlation to it all right sweet deal
24:50we covered a decent amount so far we've
24:52talked about the origin we know where
24:53it's located we talked about its course
24:54we talked about the structures that it
24:56supplies and their functions now let's
24:58do some clinical correlation real quick
25:00okay so step by step here let's say that
25:03we talk about different types of lesions
25:06we talk about nuclear
25:09lesions okay so inside of the brain stem
25:12then we talk about
25:15peripheral lesions so along the course
25:19okay nuclear lesions this is where I
25:21wanted to take some time to talk really
25:23briefly about what's called Weber's
25:24syndrome and Benedict syndrome very hard
25:28to to uh separate image- wise you have
25:30to look at certain symptoms a little bit
25:32differently okay so what are these two
25:33different types one is actually called
25:36Webber
25:37syndrome and the other one is actually
25:40called Benedict
25:43syndrome okay so this is interesting
25:45this is an interesting one because you
25:47have to look for certain types of other
25:49symptoms within the individual really
25:52quickly do you guys remember where the
25:54OC motor nerve is good recap on the
25:57sides of the pical grain matter what's
26:00right next to it say it out loud at home
26:03parasympathetic fibers what's on the
26:06sides of this
26:08medial
26:09liscus over here medial
26:14liscus just because we already put it
26:16like this what structure even though it
26:17should be red what's right here red
26:21nucleus which is for the rubber spinal
26:23pathway then we had another structure
26:27right here anterior to this this and
26:29this is going to be
26:30the Crux cerebri and the Crux cerebri is
26:34going to be specifically where the
26:35descending corticos spinal fibers are
26:37and then last but not least it's located
26:40at the level of the superior calculus
26:44all right sweet goodness we got
26:46that now if you remember we said that
26:48the third nerve might run this way out
26:51like this and out like this
26:55right parasympathetic fiber same thing
26:58they're going to come like this and then
27:00they're going to come like this there's
27:03two different types of nuclear lesions
27:04that could develop whether it be due to
27:06some type of infarction a tumor an
27:09abscess whatever demolation of the axons
27:12let's say that there was a
27:16lesion that
27:18developed right
27:22here and another lesion that develops
27:26right
27:29here okay so two lesions have developed
27:33we have to differentiate between which
27:35one it is okay for the anterior lesion
27:39the one that's affecting the ocular
27:40motor nerve as it's exiting and it's
27:42affecting the Crux cereb you have to
27:44remember what was the Crux cerebra
27:46caring descending corticospinal fibers
27:49that go into our actual muscles it's a
27:51motor pathway but if you
27:55remember we might have talked about it
27:57briefly certain times
27:58these fibers actually come down to the
28:00pyramids and they cross over and then
28:03they come out to whatever skeletal
28:04muscle they're going to
28:06supply right so this would be affecting
28:08if you damage right here you'll be
28:10affecting the actual muscles on the
28:12contralateral side of the body so you
28:15might develop what's called
28:17contralateral and if you this weakness
28:19of the muscles it's called paresis and
28:21if it's damaged completely it's called
28:23Pia right so we're just going to say
28:25that it's weakened let's just say okay
28:27but again it could progress to becoming
28:29completely damaged so it's called
28:33contralateral
28:34Hemi actually it's a sh let's say it's
28:37damaged you frecked it up all right
28:39contralateral hem plagia all right so
28:41again what is good if they're damaging
28:42these fibers right here these actual
28:44samatam motor fibers and parasympathetic
28:46fibers that are coming out at that level
28:48this would be affecting the ocular motor
28:50nerve but they don't cross since they
28:52don't cross this is going to cause the
28:54same side of the extraocular eye muscles
28:57to be affected so this is going to be
28:59called ipsilateral since it's on the
29:00same side so
29:02ipsilateral and which nerve is damaged
29:05third
29:06nerve and because that it's going to
29:08cause this paly this actual weakening of
29:11the muscles how would that manifest how
29:13would you see someone with third nerve
29:14poy what would they look like would they
29:16be you know all kinds of contorted let's
29:18see I want you guys to remember
29:21something Superior Reus controls a
29:23little bit of medial rotation inferior
29:25rectus medial rotation medial rectus
29:28medial rotation and then inferior Bleak
29:31is a little bit of lateral rotation but
29:33not too
29:34much okay but it also controls elevation
29:38so we'll put elevation here a little bit
29:41of elevation now and the superior rectus
29:44is elevation of the
29:47eyeball if you lose the function of the
29:50superior rectus infer oblique inferior
29:52rectus meteor rectus what are you
29:54primarily losing well I'm losing
29:55elevation of the eyeball and and I'm
29:58losing medior rotation medior rotation
30:00medial rotation huh so if I can't bring
30:04my eyeball in it's probably going to
30:05start wonking outwards if I can't bring
30:07my eyeball up it's probably going to
30:08start wonking downwards so what would
30:11the eyeball look like let's say that the
30:12right nerve was damaged let's say that
30:14the right third nerve was damaged so say
30:16this is the right eye left eye let's say
30:18that the right eye is affected it's
30:20going to go down and out so you're going
30:23to see the eye going like
30:24this
30:26okay it's going to go down and it's
30:28going to go out okay so when you see
30:31third nerve py you might see a
30:34Down and Out movement of the eye one
30:38other thing what other nerve is affected
30:40here the parasympathetic fibers if they
30:43can't affect the pupil what does the
30:45pupil do the pupil is actually
30:46responsible for constrict it's actually
30:48I'm sorry the parasympathetic constricts
30:49the pupil if it can't constrict the
30:51pupil what's going to happen that sucker
30:52is going to dilate right so their pupils
30:55are going to become fixed and dilated so
30:58what else will we see let's just
30:59basically give this guy like no Iris
31:01here look at
31:02this all right look at this he's got a
31:05heck of a pupil hole right so now he's
31:07going to be fixed and dilated so not
31:09only down and out movement but it might
31:10even have
31:13fixed and
31:16dilated pupils okay sweet deal so that's
31:20what we see with this person now how do
31:21I differentiate that from the other guy
31:23the Benedict which is spelled weird but
31:26that's I believe me that's how it's
31:27spelled
31:28Benedict Benedict syndrome is actually
31:31going to be the damage within the post
31:33tier part which was damaging what it was
31:35damaging the third nerve it was damaging
31:37the medial miniscus and it was damaging
31:39the red nucleus so how would this
31:43manifest remember right away the third
31:45nerve is damaged it's always ipsilateral
31:47then okay so it's going to be
31:53ipsilateral third
31:56nerve py
31:58okay next thing remember the medial
32:00liscus we might have talked about it
32:03sometimes it's actually going to have
32:05it's fibers are going to come
32:07downwards this is an ascending pathway
32:10actually so if you were to let's say
32:11that we're actually having propriate
32:12reception from the same muscle here
32:14propriate reception from this muscle
32:16whether it be from the muscle spindles
32:18or the Gogi tendon organs or the joint
32:19kinesthetic receptors it's going to move
32:21up what's called the dorsal
32:22spinothalamic tract and then it's going
32:24to get up to the medulla where the
32:26nucleus gillus and the nucleus catus are
32:29and then what's happened is it's going
32:30to cross over to the opposite side and
32:33it's going to come up here right so if I
32:37damage this medial liscus I'm going to
32:39lose loss of proprio reception and touch
32:42to the actual area on the controlateral
32:45side so I'll have what's called
32:47controlateral
32:51loss of sensation which is like
32:55hemianesthesia and maybe even proprio
32:59reception
33:01okay last thing I'm affecting their red
33:04nucleus now the red nucleus Let's
33:06Pretend now that I bring it down here in
33:10red I'm going to bring it down here in
33:12red it actually comes downwards and then
33:14it actually crosses right away and it
33:16goes to the other side and goes to these
33:20distal limb flexors so same thing with
33:23this guy it would actually cross over
33:25come downwards and go to the distal
33:27lymph flexors if you damage the red
33:30nucleus then you're going to have
33:32contralateral actually what weakness of
33:35the uh the wrist flexors right some of
33:38the wrist flexors also because you're
33:40damaging that this person develops
33:42what's called Tremors what's called
33:44flapping trimmers so that's another sign
33:46because of the rubos spinal pathway
33:48being affected so they have what's
33:49called
33:53contralateral limb weakness distal limb
33:55weakness
33:58or hem
33:59plasia if it's completely damaged
34:03and produces
34:07flapping Tremors all right sweet deal
34:11that's that one another thing what if I
34:14actually developed peripheral lesions
34:16Superior cerebella artery develop a b
34:19bar aneurysm posterior CRA artery but
34:21develop a bar aneurysm I compress the
34:23nerve if I compress the nerve I might
34:25lose function of it right excuse me what
34:28else let's say you know there's a
34:31temporal lobe right here there's a
34:33medial part of the temporal lobe called
34:35the
34:36uncus sometimes what can happen is due
34:38to high intracranial pressure the uncus
34:41can actually herniate through a small
34:42little space okay due to high
34:45intracranial pressure maybe someone has
34:47a intracranial bleed for whatever reason
34:49a high intra cranial pressure can
34:50actually cause a uncle herniation and
34:52the uncus can compress the third nerve
34:55and that could also cause problems what
34:57usually it's going to first damage the
34:59actual parasympathetic fibers and cause
35:01fixed and dilated pupils later on it
35:03actually might cause the down andout
35:06movement also it's running in the cavern
35:08of sinus so for whatever reason let's
35:11say that this was this artery here this
35:13was called the internal cored artery
35:16let's say that for whatever reason
35:19someone
35:20develops an aneurysm of the internal
35:22cored artery that could compress the
35:24third nerve
35:26or the cavernous sinus it could actually
35:29get infected you know if there's like
35:30menitis that could actually maybe flare
35:33that up or if you have what's called
35:37cavernous sinus
35:40thrombosis okay which is actually a
35:43thrombosis of the internal cored artery
35:45or maybe if some type of infection
35:47actually spread to the area from maybe
35:49the actual paranasal sinuses okay and
35:51then last thing is maybe some type of
35:53trauma what if you actually got blasted
35:55in the face by
35:58someone and it actually broke the actual
36:01maybe the part of the orbit or the
36:02superior orbital fissure and it actually
36:04compressed these actual nerves also that
36:05could also cause that problem too last
36:08but not least was this whole Vasa
36:10nervosum I didn't just mention it for
36:11the fun of it in certain situations like
36:16diabetes
36:19mtis they have microvascular changes
36:22like aneurysms basically little
36:24microvascular aneurysms of these little
36:26vessels these micro vessels is going to
36:28the actual somatomotor fibers right so
36:31in this situation when someone has
36:32diabetes metis it could actually damage
36:35the somatomotor fibers by causing these
36:38microvascular aneurysms which affects
36:41the blood supply to the actual
36:42somatomotor fibers so what would these
36:44people develop as a result to this
36:46they'll develop that down andout
36:48movement of the eye another one is
36:50people who have high blood pressure very
36:52persistent high blood pressure can also
36:53cause this too hypertension very chronic
36:56hypertension
36:58okay so Ninja nerds in this video we
37:01covered a lot of information about the
37:02ocular motor nerve we covered a lot of
37:04stuff I really thank you guys for
37:05sticking in there and watching this
37:07video If you guys enjoyed please hit the
37:08like button comment down in the comment
37:10section and please subscribe as always
37:11Ninja nerds until next time