neuro anatomy toutrial[1]

7/28/2019 Neuro Anatomy Toutrial[1]

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Brain stem frontal view :

*The doctor indicated :

-medulla oblongata

-anterior median sulcus & the

pyramids on either sides .

*pyramid contains corticospinal

& corticonuclear fibers .

*cortico-nuclear fibers : goes to cranial nerve motor nuclei in the medulla

oblongata which are nucleus ambigiuos & hypoglossal nerve nucleus .

*cortico-spinal fibers : the lower part of the anterior median sulcus becomes

obliterated because of the crossing fibers of the corticospinal tract .

*On either sides of the midline there is the olives which is made by the inferior

olivary nuclei .

* The superior olivary nucleus is located in the pons which relay the auditory fibers

with the nucleus of the trapezoid body .

(superior olivary nucleus+ nucleus of the trapezoid body= relay the auditory fibers)

- About The CRANIAL NERVES :

You should know :

1- how to test each one of them cranial nerve function

2- signs & symptoms for cranial nerve lesion

3- the outer features about different parts of the brain stem : medulla,pones,mid brain

4-Internal structures : nuclei, ascending and descending tractsetc.


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*Between the inferior

olivary nucleus (Olive) and

the pyramid : there are "the

hypoglossal nerve rootlets "

.

* between the olive and the inferior cerebellar peduncle : there are" the rootlets of

the 9th

, 10th

and 11th

cranial nerves , cranial accessory nerve '11th

' " .

* But , the spinal accessory nerve '11th

' comes from the anterior horns of the upper

five cervical segments and ascends through the foramen magnum to join the cranial

accessory nerves then they both go out through the jugular foramen then get

separated. Then ,after coming out of the jugular foramen, the cranial accessory will

join the vagus ..

*Between the pons and the medulla oblongata :

1- There is the abducente nerve .

2- Lateral to (abducente nerve) : Roots of facial nerve: motor & sensory "2 roots" .

3- Lateral to (roots of facial) : The vestibulochochliar nerve which is sensory nerve

vestibularfibers are medial & the chochliar are lateral .


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* The vestibulochochliar and Facial nerves : Both pass through the internal acoustic

meatus:

1- The vestibulochochliar 'Sensory' and sensory root of the facial "nervus

intermedius" ; go into (enter) the internal acoustic meatus

2- The motor root of the facial ; goes out (exit) of the internal acoustic meatus ;

( But all of these fibers exist in the internal acoustic meatus )


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Pons :* the doctor indicated:

1- In the Midline : basilar groove which contain the basilar artery.

2- ponto-cerebellar fibers "transverse running fibers" : araise from the pontin nucli

of one side and cross to the opposite side in the middle cerebellar puduncle .

- the pontin nuclei are controlled by cortico pontine fibers its like saying cortico

ponto cerebellar

-so, the cerebral cortex control the cerebellum through the ponto-cerebellar fibers .

* At the antrolateral surface of the pones : there is the trigeminal (5th

) nerve roots

a small one and a big one :

- the small one is motor and the big one is sensory.

- the motor is medial and the sensory is lateral .

Q :- if there was a lesion or any kind of compression in one of these nerve fibers

"Fiberomeningoma , tunor" - the ones in the internal acoustic meatus-

what would your patient have ?

A/ logically;

- if the facial nerve is compressed the patient will have facial nerve paralysis all the

face will be paralyzed "lower motor neuron paralysis" .

- if the chochlear nerve was affected it will be paralyzed which cause epsilateral

deffeness .

- if the vestibular nerve was affected this causes nausea, vomiting , vertigo and

nistagmus on the same side.


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Mid brain:*the doctor indicated:

1- cerebellar puduncles2- In The Anterior surface , crus cerebri : Between them (the 2 crus cerebri) we find

the inter pedincular fossa .

3- Inter pedincular fossa : we can see some perforations posterior perforatedsubstance

- the center branches of the posterior cerebral pass through posterior perforatedsubstance .

- between the two crus cerebri emerge the oculomotor nerve .- The trochlear nerve come from the back , on the sides of the mid brain


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-Between olive and inferior cerebellar puduncle are : glossopharygeal 9th

, vagus 10th

and cranial part of accessory nerve 11th

.

- On the side of the brain ,below inferior coliculus, we find the trochlear nerve:

emerging from behind and coming on the side to go to the cavernous sinus.

- On the front of the brain , we find the occulomotor nerve.

- Lateral and medial geniculate bodies : are connected by " superior and inferior

bracia" to the "superior and inferior coliculi" .

- On the back of medulla oblongata , the

lower part of the medulla oblongata is

closed and it have a central canal.

- On the either side of posterior mediansulcus we have 2 tubercles , we have

gracile tubercles and lateral to them

cunate tubercles . thease 2 tubercles are in

continuty with posterior column tract

(fasciculus graciles and fasciculus

cunatous) which come from the spinal

cord.

- Gracilis nucli on either side of midline and cunatous lateral to it.

- Upper part of medulla oblengate is open forming the lower part of the floor of the

4th

ventricle.


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-The Hypoglossal triangle show us that the Hypoglossal nucleus lying on the floor of 4th

ventricle.

- The Vestibular area : contains the vestibular nucleus (superior ,inferior ,medial and

lateral).

-The Vegal triange for dorsal nucleus of the vegus parasympathetic nucleus .

- In upper part of the pons , on the either side of median sulcus is medial eminence .

-In the lower part of the medial sulcus is facial caliculus which is made by nucleus of

abducent nerve that cause bulging of facial coliculus .

-Straiae medullaris thalami : are fibers come from anterior arcuate neucli (which are

displaced pontine nucli ) , they pass through the depth of the medulla and appear in

the floor of medulla as Straiae medullaris and go to cerebellum through inferiorcerebellar punduncle.

- Superior caliculus is a centre for visual reflexes . (for visual)

- Inferior coliculus is a center for auditory pathway. (for hearing)

- Below the Inferior coliculus we find the emerging trochlear nerve.


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Medulla oblongata :- The Medulla oblongata is viewed at 4 levels :

*Lowest level of medulla oblongata :

- At the lower level of medulla oblongata we have decusssaion of pyramid.

- These decussating fibers tends to obliterate the anterior median fissure in the lower

part of medulla oblongata.

- About (80 - 85 %) of fibers cross to form lateral corticospinal tract, the remaining

(15%) fibers descend on the same side to form anterior corticospinal fibers.

- In the figure we can see spinocerebellar tract lateral spinothalamic tract (both in the

lateral side of medulla oblongata).

- We can see spinal nucleus and spinal tract of trigeminal nerve, and they receive pain

and temperature sensation of "3 divisions" of the trigeminal nerve.

- The spinal tract of trigeminal nerve is lateral to the nucleus of trigeminal nerve. The

nucleus of trigeminal nerve is medial to the tract of trigeminal nerve.

- The three divisions of the trigeminal nerve are presented upside down ,so that the

ophthalmic division will be at the lowest part and mandibular division will be at thehighest part. They receive pain and temperature sensation.


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*Higher level of Medulla oblongata :

- At the higher level we will find a decusssaion of the medial leminisci.

- The fibers which reaches to the nuclei gracilis and nuclei cuneatus form the posterior

column tract are going to end at this level. The second order neuron is going to cross in

front of the closed part of medulla (where is the central canal located) and they goingto form medial leminisci. So the medial leminisci cross at a higher level than the

decusssaion of pyramid.

- At the higher level, the medial leminiscus occupying an anteroposterior position in

the medial part of medulla oblongata, behind it is the tectospinal tract (and we can see

the medial longitudinal fascicles).


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Q :-

- The medial longitudinal fascicles is confined to medulla oblongata, Will you agree?

- What is the medial longitudinal fascicles?

A/ These are fibers that connect the vestibular nuclei to the cranial nerve nuclei of the

third, the forth and the sixth cranial nerves , and the idea of this ; is to coordinate the

movement of eyeball. So this is why the vestibular nerves are connected to it.

The medial longitudinal fascicles is not confined to medulla because the third and

fourth cranial nerve are found in the midbrain. It connects between third, sixth

and fourth cranial nerve,So it is not going to be only in the medulla oblongata, it

will be also in midbrain and Pons (it extend in the brain stem).


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Tongue and Hypoglossal nerve :- In the floor of 4th ventricle there is hypoglossal nerve nucleus , and dorsal nucleus of

the vagus at the surface of the floor of ventricle.

- Fibers coming out of the Hypoglossal nerve nucleus are lower motor neuron.

So if there is a lesion involving hypoglossal nerve and the fibers coming out of it on theleft side, there will be paralysis of the muscles of the tongue in the same side (left side)

, and if you ask the patient to protrude his tongue it will deviated to the same

paralyzed side (lower motor neuron paralysis) .

- The upper motor neuron are corticonuclear fibers coming from the cortex to nucleus.

- Regarding to corticonuclear fibers, all motor nerves cranial nuclei receive from both

cerebral hemispheres except the lower part of facial nucleus and the neurons of the

hypoglossal nucleus that supply genioglossus they receive from opposite side

hemisphere .

- So if we have an upper motor neuron lesion , the fibers that supply the opposite side

of genioglossus if they intrubted the genioglossus will be paralyzed.

(the genioglossus is the muscle that protrude the tongue ,so if it is paralyzed , the

opposite muscle will deviate the tongue to the opposite side - the same side as the

lesion ).

*Again : with regard to the upper motor n. , the fibers coming from the right

hemisphere going to supply the left genioglossus , and if the genioglossus paralyze so

the tongue will deviate to the left (the lesion in the right upper motor n.)

How to distinguish between upper motor neuron paralysis and lower motor neuronparalysis?

-In case of lower motor neuron , there is atrophy and fasciculation.

-In case of upper motor neuron , patient protrude his tongue to the left side (opposite

site) without fasciculation and atrophy (the size of the tongue is the same).

-Hypoglossal nerve supplies all intrinsic muscles of the tongue and all extrinsic except

palatoglossus, it is purely motor nerve.

So the Propioception "Sensory sensation" of the tongue is carried by trigeminal nerve

not by hypoglossal nerve.


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Hypoglossal Nerve :- It supply all the intrinsic muscles of tongue. (control the shape).- It supply the extrinsic muscles except the palatoglossus . (control the movement).- It is purely motor nerve.- There are no any sensory fibers.- The proprioception of the tongue is carried by trigeminal nerve notby hypoglossal

nerve.

- the arcuate nucleus is in the medial part of the medulla oblongata .

The arcuate nuclei :-The arcuate nuclei is a displaced pontine nuclei .

-So The arcuate nuclei receive corticopontine fibers from the cortex and they send

pontocerebellar fibers.

-Some ofthe pontocerebellar fibers, that they sent , go to different parts in the

surface of the medulla as external arcuate fibers to the inferior cerebellar pedancle .

Other fibers pass through the depth of the medulla and appears in the floor of 4th

ventricle as striae medullares .


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Nucleus ambiguous :- It is located laterally in the medulla oblongata .

-It is the nucleus form which the motor fibers for the glossopharyngeal , vagus and

cranial part of the accessory nerve will come out .

-The Nucleus ambiguous is controlled by both side (All of them =9,10,11th CN) . So, if

there is an upper motor neuron lesion they will not be affected because they getting

from the other side.

-The nucleus ambiguus is impeded deep within reticular formation .

- The reticular formation carries autonomic fibers (sympathetic and parasympathetic)

that go down to control the lateral horns in the thoracolumber segments and S2, S3

and S4segments.


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The vestibular nuclei :- There are 4 vestibular nuclei:1 Superior vestibular nucleus.

2Inferior vestibular nucleus (in the upper part ).

3medial (middle) vestibular nucleus.

4Lateral vestibular nucleus (in the lower part ).

Olivary nucleus :-On the dorsal aspect of the inferior olivary nucleus we find the spinal lemniscus.

-Spinal lemniscus consist oflateral spinothalamic tract , anterior spinothalamic tract

and the spinotectal tract.

-Laterally , the spinal tract and close to it the nucleus of trigeminal nerve.

-The cochlear nuclei appear in the dorsal and anterior aspect of the inferior cerebellar

peduncle. So, the cochlear nuclei are fund on the surface of the inferior cerebellar

peduncle.


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The blood supply to the medulla oblongata :1Medial part is supply by vertebral artery (mainly by anterior spinal branches of the

vertebral artery ) .

2Lateral part is supply by the posterior inferior cerebellar artery (P.I.C.A) and this is

also a branch of the vertebral artery.

The hypoglossal nerve nucleus :-The nucleus receives from both

cerebral hemispheres

(corticonuclear fibers). But the

fibers that go out to to supply

the genioglossus muscle they

are controlled only from the

opposed side . So, if the

hypoglossal nerve of this site

(after coming out from the

nucleus) is paralyzed the tongue

will deviate to the same side

because the other genioglossus

muscle will pull it to the otherside.

So,

1In case of the lower motor

neuron lesion as we said the deviation will be to the same side.

2In case of an upper motor neuron lesion the deviation will be to the opposed side.

(And we know how to differentiate between them).

Inferior olivary nucleus :-It receives the afferent spino-olivary fibers .

-And it sends olivocerebellar fibers to the cerebellum.


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The spinal accessory nerve :-The spinal accessory nerve arises from the central group of neurons found in the

anterior horns of the upper 5cervical segments. And the fibers that come out from

these neurons are going to pass between

the anterior and the posterior horns and

they join each other and eventually go

through the foramen magnum, And ones

they comes out of the jugular foramen

they separate from each other.

-The cranial root is going to join the vagus

nerve.

- The spinal root will go to supply thesternomastoid and the trapezius muscle.

The cranial accessory nerve :-Its cell bodies are in the Nucleus

ambiguus.

-The arrangement in the nucleus ambiguus

is like this:

1At the upper part is the glossopharangeal nerve.

2At the middle part is the vagus nerve.

3At the lower part is the cranial accessory nerve.

-The cranial accessory nerve ,ones it separate from

the spinal accessory and joined the vagus below its

inferior ganglion, it going to be Joind with the vagus

nerve to supply pharyngeal , laryngeal and palate

muscles .So, the cranial accessory nerve will supply

the pharynx , the larynx and the palates. While the

spinal accessory is going to supply the

sternomastoid and trapeziues muscle. (in the Snell

text book ,7th

edition, page 356,line 4 .He write

sternocleidomastoid instade of sternomastoidmuscle ) .


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Accessorynerve

cranialaccessory nerve

pharynx larynxpalate

(soft palate)

spinal accessorynerve

sternomastoid trapeziues

- So, the accessory nerve thus brings about movement of the soft palate , pharynx ,

and larynx and controls the movement oftwo large muscles in the neck.

Clinical test for the spinal accessory :-The usual test for the spinal accessory by asking the patient to turn his head to the

opposite side against the resistance and we will note the sternomastoid musclecontracting.

Summary : The spinal accessory nerve:Arise from the upper 5 cervical segments.

Its fibers are acceding like this:1They enter the skull throw the foramen magnum .

2Joined with cranial accessory. To form one nerve called accessory nerve.

3As soon as the accessory nerve come out from thejugular foramen, it will be divide

again to spinal and cranial accessory roots(nerve).

4The spinal accessory root then (after separated) runs downward and laterally and

supply the sternocleidomastoid and trapezius muscles.

5The cranial accessory root then (after separated) joined the vagus nervebelow theinferior ganglion and goes to supply pharynx, larynx and palates.


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Accessory nerve (11th

nerve):

Two parts:

1-crania accessory that supplies laryngeal, pharyngeal and palatal muscles.

2- spinal accessory that supplies sternocledomastoid and trapezius muscles.

We test for spinal accessory by asking the patient to turn his head to opposite side

against resistant and we note sternocledomastoid is contacting. Or lifting the shoulder

for the trapezius.

The pathway of spinal accessory is formed of 5 upper cervical segments , the fibers

ascend and enter to foramen magnum then they join with cranial part forming one

nerve then they separate as soon as the come out of jagular foramen. The cranial part

joins the vagus nerve below the inferior ganglion.

Hypoglossal nerve (12th

)

Most properties receive from both cerebral cortices execept the fibers that supplies

the neuron which supplies geniuglossal muscle receive only from opposite side.

The hypoglossal nerve supplies all the intrinsic mucle of the tongue and all the extrinsic

muscle except the palato-glossal muscle.

We test for the nerve by asking the patient to protrude his tongue.


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Glossopharyngeal nerve (9th

):

It supplies the parotid glands and supplies taste and common sensation for the

posterio one third of the tongue.

The caurse of the nerve to the parotid gland:

Inferior ganglia of Glossopharyngeal tympanic branchtympanic plexus lesser

petrosal nerveotic ganglia parotid gland.

It has motor nucleus, salivatory nucleus, and sensory nucleus ( tractus solitarius).

The motor nucleus is found in the upper part of nucleus ambigous and supplies one

muscle (stylo-pharyngeal muscle). It is difficult to test for its motor function.

The parasympathetic nucleus ( inferior salivatory nucleus) supplies the parotid gland.

The nucleus of tractus solitarius is going to receive taste fibers from facial, vagus and

glossopharyngeal nerves. So it is foundin the pons (receive from facial) and medulla

oblongata ( receive from glossophryngeal and vagus). These were first order neuron

fibers.

Second order neuron fibers cross to opposite side, going to ventral-postro-medial

nucleus of the opposite side in the thalamus.(DO Not ascend in the same side).

Then the third order neuron fibers ascend through internal capsule to chorona radiata

to lowest part of post central gyrus.


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The vagus nerve (10th

):

It has got motor nucleus from the nucleus ambigous which is controlled from both

cerebral hemispheres.

It has got dorsal nucleus of vagus ( para-sympathetic nucleus) which control

pulmonary, cardiac and gastro-intestinal down to the junction of middle and distalthird of transverse colon.

It has got nucleus in tractus solitarius which receive fibers from the front of epiglottis.

( it has the same pathway as the glossopharyngeah has). The fibers cross to opposite

side to ventral-postromedial then to post central gyrus.

How do test for vagus nerve?

It supplies pharyngeal, laryngeal and palatal muscles. We test the laryngeal muscle by

using laryngo-scope directed to vocal cords and ask the patient to say (aaaaaa) and we

can see the vocal cord moves. Or asking the patient to say (aaaaa) and we note the

soft palate moves.


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If we have a lesion in nucleus ambigous so the fibers that supplies muscles of pharynx,

larynx,and palate will be paralysed. the patient will have (dys-phornia, dys-artheria,

horseness of voice) and dysphagia (difficulty in swallowing) and regurgitation of fluids

through the nose because the soft palate will not be raised.

Dorsal nucleus of the vagus: we can see there is connection between the nucleus of

tractus solitarius and the nucleus of glossopharyngeal nerve.

Now, we talked about "gag reflex" and we said that gag reflex involves the innervation

of the oropharynx by the glossopharyngeal nerve.

See the fibers going to the

nucleus of tractus solitarius;

so it is not only recieving taste

but also recieving sensoryfibers. He will lose touch from

the glossopharyngeal and

then it relays the information

to the nucleus ambiguous.

Nucleus ambiguous will come

out as fibers either through

the glossopharyngeal to the

stylopharyngeus or through

the vagus to the pharyngeal

muscles.

When you touch the region of

the oropharynx, the patient

will gag. So, the reflex involves afferent glossopharyngeal ,efferents both

glossopharyngeal and vagus.

We have also carotid sinus reflex. We know that the internal carotid has got the

carotid body which is sensitive to increase in arterial pressure. This carotid body is

supplied by the glossopharyngeal nerve.

Again, the information is carried from the carotid body to the nucleus of tractus

solitarius; from there, we have internuncial neurons that connect with the

parasympathetic nucleus of the vagus and also with the reticular formation in the

ascending autonomic fibers in the reticulospinal tract.


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The effect of this will be stimulation of the dorsal nucleus of the vagus producing

bradycardia and stimulation of the descending autonomic fibers to the lateral horn in

the thoraco-lumbar segment. This will cause vasodilatation and this will result in

hypotension.

Now, we see the blood supply of the brainstem: the medulla in its medial part is

supplied by the vertebral branches (mainly the anterior spinal arteries) and in its

lateral part by the posterior inferior cerebellar artery. The pons as we see has got the

basilar artery setting in the anterior surface. The basilar artery gives the superior

cerebellar and anterior inferior cerebellar artery. So, branches from the basilar as well

as from these cerebellar branches supply the pons.

At the end, the basilar artery divides into two posterior cerebral arteries in most

people (70%-75% of people) and the midbrain receives -in this percentage of people-

blood supply from the terminal branches of the basilar artery and from the posterior

cerebral artery. These two arteries supply the midbrain.


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Now, the lateral medullary syndrome involves a number of structures. It involves the

nucleus ambiguous, the reticular formation, the vestibular nuclei, the spinal nucleus

and tract of trigeminal nerve, the spinal lemniscus or the spinothalamic tract and the

inferior cerebellar peduncle. So, in lateral medullary syndrome you should think about

these structures.

Nucleus ambiguous meaning palatal, pharyngeal and laryngeal muscles will be

paralyzed. There will be dysphagia, dysphonia and regurgitation of fluid through the

nose .

Now, if you take the spinal lemniscus. We said that mainly the lateral spinothalamic

tract, there will be loss of pain and temperature on the opposite side because this is a

crossed tract.

Here is the spinal tract and the nucleus of the trigeminal nerve concerning pain and

temperature. Then, there will be loss of pain and temperature on the ipsilateral side.

Vestibular nuclei will be involved; the patient will have nausea, vomiting, vertigo,

nistagmus and so on.


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Inferior cerebellar peduncle is involved then the patient will have ataxia.

Reticular formation of the patient will have Horner's syndrome. There will be ptosis,

miosis, anhydrosis and enophthalmus.

In medial medullary syndrome, we are talking about the pyramids, medial lemniscus

and the hypoglossal nerve. In this condition, the patient will have upper motor neuronparalysis contralaterally because they go down to the lowest part of medulla and then

they cross. They are crossed. Medial lemniscus is concerned with proprioception,

discriminative touch and vibration sense. So, there will be loss of these sensations on

the same side because the medial lemniscus brings information from the same side.

About medial lemniscus decussation: above the decussation of the pyramid (the

arcuate fibers), they cross and then meet the medial lemniscus. So, there will be loss

of these sensations on the opposite side.

There will be paralysis of the hypoglossal nerve on the same side. The effect will be

lower motor neuron paralysis. If it involves the right side, the tongue will deviate to the

right.


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Pons

It divide into two parts:1- Basilar part (basal)2- Tegmental part

Basilar part It contains pontine nuclei which give rise to fibers that cross to the opposite side

on the middle cerebellar peduncle (transverse fibers) & are controlled by

corticopontine fibers

These transverse fibers which run transversely from one side to opposite sideare actually called pontocerebellar fibers

Corticospinal & corticonuclear fiber are interspersed between transverse fibersAt the level of the pons, corticonuclear fibers to hypoglossl nerve nucleus is

most important corticonuclear fibers because it controlled only from the

opposite side

If there is lesion in the basilar part ,corticospinal & coticonuclear fibers to thehypoglossal nerve nucleus will be injured

Lesion in the corticospinal fiber at the level of basal part the effect will be on theopposite side because they will cross in the pyramid (upper motor neuron

paralysis of corticospinal fiber).So there is spastic paralysis.

So, Contralateral spastic paralysis in the lesion of corticospinal fiber.

In addition, deviation of the tongue due to lesion in the corticonuclear fiber tothe hypoglossal nerve

Not just corticospinal, corticonuclear& pontocerebellar is injured also the facial& abducent nerve will be injured (lower motor neuron paralysis).

Because the abducent & facial nerves both pass through the basal part of thepons

This result in paralysis of all the facial muscles due to lower motor neuronparalysis of the facial muscles &

Internal squint due to paralysis of the abducent nerve Fiber that comes from any nucleus is lower motor neuron.


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Test of the abducent nerve

By asking the patient to look laterally because the abducent supplies lateralrectus

So, paralysis of the abducent leads to internal squint because lateral rectuswon't be functioning & medial rectus will be working well

Test of the facial nerve

1- Ask the patient to show his teeth symmetrically2- To close the eye firmly & try to lift up his eyelid3- To blow his cheekSo, paralysis of the facial nerve the patient cannot close his eye, cornea will be

dry & ulcerate because blinking movement is important to bring the tears in

front of the corneaTegmental part

Medial laminsci instead of being antroposterior like in the medulla , they areoccupied horizontal position in the most anterior part of tegmentum of the pons

& they overlap trapezoid body & superior olivary nuclei

Reticular formation found in the medulla, pons& midbrain and lateral to it is theSpinal laminescus carries spinothalamic tract

At the level of facial colliculus of pons, you will see facial & abducent nuclei, butat higher level of trigeminal nuclei you will see the trigeminal nerve nucleus

(table 5-2 in the book)

Medial longitudinal fasciculus is found in the pos & brainstem so, foundthroughout the brainstem

Basilar part of pons has got: corticospinal which is going to cross to the oppositeside. corticonuclear which is go down to the opposite hypoglossal nerve & affect

fibers that supplying the genioglossus muscle. pontocerebellar fibers.

The tegmentum has got the nuclei of the facial nerve which is behind the lateralpart of the medial laminescus

Abducent nerve nucleus making a bulge which is called facial colliculusThe doctor mentioned the presence & absence of reticular formation, nuclei & sensory

& motor tracts at the level of facial colliculus & trigeminal nuclei of the pons. So, it is

helpful to study (5-2) table, 6th edition.


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Nerves related to the pons:

The vestibular nerve:

It comes to the vestibular nuclei. Its ganglion is found in the internal acoustic meatus.

Its peripheral fibers** come from the utricle, saccule (structures in the ear related to

the vestibular system and they are concerned with the static equilibrium i.e. positionof the head in the space) and semicircular canals (in their ampullated -i.e. having an

ampulla- end, there are hair cells concerned with dynamic equilibrium i.e. the

movement of the head). Some of the vestibular fibers do not end in the vestibular

nuclei but they go to the cerebellum. In addition to that the vestibular nuclei receive

some fibers from the cerebellum. So the afferent fibers coming to the vestibular nuclei

are mainly from vestibular ganglion but some of them are coming from the

cerebellum.

**(note that these are bipolar neurons which have two extensions, one is coming to

the ganglion called peripheral fiber and one is leaving it called central fibers)


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The efferent fibers that leave the vestibular nuclei:

The vestibulospinal tract leaves the lateral vestibular nucleus to the anteriorhorn cells. Its function is to stimulate the extensor muscles and inhibit the

flexor muscles so it is very important to keep our sitting position otherwise

we will fall either to the anterior or the posterior sides.

Fibers go to the medial longitudinal fasciculus and coordinate the function ofthe three nerves that supply the extraocular muscle, the 3

rd, 4

th(both in the

midbrain) and 6th

(found in the pons).

Fibers go to the ventral posteromedial nucleus of the thalamus and fromthere they leave to the lowest part of the postcentral gyrus.

The vestibular nuclei are very important to maintain our balance, and if there is a

lesion involving the vestibular nuclei, the patient will have nausea, vomiting, vertigo

and nystagmus. We can test its function by syringing (injecting) some warm water

into the ear this will create a convection current (the transfer of heat through a fluid

(liquid or gas) caused by molecular motion) or by rotating chair.

Cochlear nerve:

Its ganglion is called spiral ganglion because it is found in the cochlea and it takes the

cochlear spiral shape. Its peripheral fibers come from the organ of corti (the hearing organ of

the inner ear). The central fibers collect to form the cochlear nerve which runs through theinternal acoustic meatus with the facial nerve.

So if we had a tumor compressing these two nerves at the internal acoustic meatus, we will

have ipsilateral deafness and ipsilateral lower motor facial paralysis.

These fibers reach the anterior and posteriorcochlear nuclei in surface of the inferior

cerebellar peduncle. Second order neuron fibers mostly cross to the opposite side and end in

the posterior nucleus of the trapezoid body and superior olivary nucleus. Some of them (2nd

order neuron fibers) end on the same side. Whether they end on the same or the oppositeside they will have the 3

rdorder neuron forming the lateral lemniscus. Within the lateral

lemniscus there is a nucleus that receives some of these fibers. But most of the fibers will end

in the inferior colliculus and a few fibers will end in medial geniculate body. But eventually

all the fibers will end in the medial geniculate body (one of the nuclei of the thalamus

receiving all the sensations except the olfaction). Then the fibers leave the medial geniculate

body to the retrolenticular part of the posterior limb of the internal capsule . And then they

pass through corona radiata to the upper middle part of the superior temporal gyrus near to

the posterior ramus of the lateral sulcus, this is where we find the auditory cortex. We test

for the auditory (cochlear) nerve by a tuning fork. Read about Rinne and Weber tests.


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(the doctor gave a very small idea about the Rinne test and he did not mention even the

names of the tests)

How you test for the auditory nerve? --> by the Tuning fork. We ask the patient to

close his eyes and bring the tuning fork and ask him if he if hearing. If he got

conduction deafness due to some problem in the ossicles or the middle ear we put the

base of the tuning fork on the bone and ask him if he can hear.


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Facial nerve:

It has Main motor nucleus which supply the muscles of facial expression and also

supplies the stapedius muscle (the stpedius and it's pyramid is found in the middle ear

cavity so if there is a patient with ottits media this nerve may become involved and the

stapedius becomes paralyzed and the patient complains of hyperacousis (loud voices

because the stapediusis isn't tensing the tympanic membrain so it will become laxed

and vibations will become exaggerated)

The facial nerve has also sensory ganglion which has the cell bodies for taste. Taste

either comes from the palat (greater petrosal nerve) or from the anterior two thirds of

the tongue through the corda tympani nerve

So the facial nerve has sensory roots and motor roots which supplies the muscles of

facial expression together with the stylohyoid and posterior belly of digastric but themost important other than the facial expression is the stapedius

So if there is damage to the facial nerve above this level (before it give the nerve to

stapedium)(57:40) or within the middle ear you can get hyperacousis know what

level the doctor was pointing in the diagram


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The main motor nucleus its fibers are hooking around the abducent nerve nucleus

(know where is the facial colliculus)

The parasympathetic nucleus is called the superior salivatory nucleus. Remember that

the inferior salivatory nucleus one of the nuclei of glossopharyngeal nerve. the

superior salivatory nucleus is called lacrimal nucleus because some of its fibers supply

the lacrimal gland where as the salvatory part supply the submandibular and

sublingual salivary glands and also supplies nasal and palatine glands

The nucleus of tractus solitarius is going to receive fibers which are going from the

Geniculate ganglion. These central fibers are going to the nucleus of tractus solitarius.

The highest part of the nucleus of the tractus solitarius is for the facial nerve. The

fibers cross to the opposite side then ascend to the ventral postromedial nucleus of

the thalamus --- the rest of the story is the same.

We test for the facial nerve by closing the eye, showing the teeth or blowing. If there is

a paralysis the eye won't be closed and the angle of the mouth on the same side will

drop and if the patient eats you will find the food accumulate in the vestibule of his

mouth


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Cauda tympani

It joins the lingual nerve

The fibers from the superior salivetery nucleus are going to relay in the submandibular

ganglion to supply sublingual and submandibular salivary glands.


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Paralysis of facial nerve

As we said corticonuclear fibers is supplied by

the two hemisphere except two . Hypoglossal

nerve is an exception, facial nerve is another

exception. The upper part of facial nucleus

receive from both cerebral hemispheres but

the lower part receives only from the

opposite cerebral hemisphere. Thats why

when we have an upper motor lesion

involving the corticonuclear fibers to the

facial nerve this means that the lower half of

facial nucleus on the opposite side will be

affected and will show lower face paralysis

on the opposite side (this will be upper motor

neuron paralysis).

This is the way to differentiate between

lower motor neuron involving the whole face

and upper motor neuron paralysis involving

the lower part of the face on the opposite

side.

Tha pateint won't be able to close his eye

very will and will have dropping of the angle

of the mouth in the affected side.

The abducent nerve

As we said it supplies the lateral rectus muscle. If it is paralyzed it will give you internal squint. You

test for its paralysis by asking the patient to look strait lateral.


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Tigeminal nerve

It has three sensory nuclei and one motor nucleus. Sensory nucleui are the spinal nucleus in

tract of the trigeminal nerve and in the meddula oblengata (1:01:10) with the three devesions

represented upside down are for pain and temperature. Revise it

The main sensory nucleus in the pons is concerned with light touch.

In the mid brain we have the mesencephalic nucleus. Actually the main sensory

nucleus and the spinal nucleus of the trigeminal nerve they have the cell bodies the

trigeminal ganglion.

Peripheral fibers obviously come from the periphery. from skin or whatever from

sensory propioseption from muscles of the face, tongue or extraoccular muscle or

whatever they have except for propioception (pain, tempretue, crude touch and

pressure all got the cell bodies in the trigeminal ganglion) central nucleus enter the

spinal nucleus(the main nucleus). Peripheral fibers come from the periphery and

central fibers enter the spinal nucleus (the main nucleus). For propioception the

sensory nucleus is found in the midbrain (mesencephalic nucleus of the trigeminal

nerve). This nucleus consists of

pseudounipolarcells. The peripheral

fibers which are carrying

propioception pass transient

through the trigeminal ganglion

(their cell bodies are not present in

it, they are found in the

mesencephalic nucleus in mid brain)

The central fibers as you see here

they cross to the opposite side and

group together to make the

trigeminal lemniscus which goes to

the ventral postromedial nucleus of

the thalamus then go to the post

central gyrus.

The motor nucleus of the trigeminal

nerve lies medial to the main

sensory nucleus.
http://en.wikipedia.org/wiki/Pseudounipolarhttp://en.wikipedia.org/wiki/Pseudounipolarhttp://en.wikipedia.org/wiki/Pseudounipolar


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Trigeminal nerve (V) : (1:01:02 -1:10:29)

- 3 sensory nuclei :

a- Spinal nucleus and the tract of the trigeminal nerve in the medulla oblongata with

3 divisions represented upside down for ( pain and temperature)

b- The main sensory nucleus in the pons for (light touch)

c- mesencephalic nucleus in the mid brain for (propioception)

* The central fibers of the 3 nuclei will cross to the opposite side and grouped

together to form (trigeminal lemniscus)

* The trigeminal lemniscus will go to the (ventral posteromedial nucleus of the

thalamus) and from there to the ( post central gyrus)

- 1 motor nucleusLies medial to the main sensory nucleus because it is in the pons

Both of these 2 nuclei(for pain , temperature , touch and pressure ) have their cell

sotrigeminal ganglionbodies in the

- Peripheral fibers come from the periphery

- Central fibers enter the spinal nucleus and the main nucleus

n the mid brainthe nucleus and cell bodies are found ipropioceptionFor-

- The nucleus is consist of pseudo-unipolarcells

- The peripheral fibers goes transient through the trigeminal ganglia (without their cell bodies)

In the pons there is a main sensory nucleus and medial to it`s motor nucleus


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Testing of the trigeminal nerve :

- The motor nucleus supplies the

(muscles of mastication)

- On examination we ask the patient

to bite hard (so the masseter and

temporalis muscle will contract )

- If there is paralysis of these

muscles we find the jaw deviated to

the affected side because ( the

trigoid muscles of the opposite side

will pull the jaw to the opposite side)

-We can test for sensation by

testing the 3 divisions of the

nerve(ophthalmic, maxillary and

mandibular)

- The 3 divisions of the trigeminal nerve don't overlap with each other

the skin over the angle of the mandible is not supplied byRemember :-

trigeminal but by greater auricular nerve


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Blood supply of pons :

1- Basilar artery

2- Anterior inferior cerebellar

artery(AICA)

3- Superior cerebellar artery (arise from

the basilar artery)

pontine syndromes :

1-caudal basal pontine syndrome

Because (it is in the caudal part in the pons involving the basilar part of the pons )

So it involves :

a - Corticospinal fibers

(1:04:40) they will descend to form the pyramid and then they cross to the opposite side

b- Corticonuclear fibers

c- Pontocerebellar fibers

So lesion will cause contralateral spastic hemiplegia of the opposite side

There will be lower facial nerve paralysis on the opposite side

Ataxiaf these are involved there will beWhich is going to the cerebellum and i


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d- The emerging 6th

and 7th

nerves

* In this case both the facial and

abducent nerves will be involved

and it is a lower motor neuron

paralysis

- So the whole face will be

paralyzed and this will mask the

question of upper motor neuron

paralysis of the facial nerve

(otherwise if these were not

involved there will be only

corticonuclear effect on the lower

half of the face) (1:05:16)

Abducent nerve medial squint

Facial nerve inability to close the eye and dropping of the angle of the mouth

2- Tegmental pontine syndrome

- ( The corticospinal fibers , corticonuclear fibers and pontocerebellar fibers) are

not involved

- (The facial nerve ,abducent nerve, and the medial lemniscus) are involved

* So there will be facial and abducent nerves paralysis as a( lower motor neuron

paralysis) and loss of propioception and discriminative touch etc on the

opposite side of the body (because the medial lemniscus has already crossed at

the level of nuclei gracillis and cuneatus ) .


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3- Complete medial pontine syndrome

Involves the upper 2 types-

4- Rostral basal pontine syndrome

It is the same as caudal basal pontine syndrome but instead of involving the 6th

and the 7th

nerves it will involve the 5th

(trigeminal ) otherwise it is the same

----------------------------------------------------------------------------------

Mid brain

2 levels 1-at the level of the inferior colliculus 2-at the level of the superior colliculus

1- At the level of the inferior colliculus

-cerebral aqueduct (which connects the 3rd

& 4th

ventricles of the brain, the CSF passes

from the 3rd

ventricle through the cerebral aqueduct to the 4th

ventricle)

- Around the cerebral aqueduct there is the central gray (on either side of it there is

the mesencephalic nucleus of trigeminal nerve

- in the anterior part there is the nuclei of trochlear nerve (when the fibers come out

they cross to the opposite side

- The inferior colliculi are involved in the auditory pathway

same sidethe effect will be in thetrochlear nerveSo if there is a lesion of the

it will be in the opposite sidenucleusbut if it is in the


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In the mid brain :

- Medial longitudinal fasciculus found throughout the mid brain because it has to

connect with trochlear nerve nucleus and occulomotor nerve nucleus

- decussation of the superior cerebellar peduncles

- Tegmentum which contains :

* The medial lemniscus ,spinal lemniscus, lateral lemniscus , and the trigeminal

lemniscus etc. (arranged in direction from medial to spinal to trigeminal )

* The lateral lemniscus ends in the inferior colliculus

Some relations :

- In front is the substantia nigra (dopaminergic neurons will be mentioned in basal

ganglia later) . substantia nigra lies behind the crus cerebri and in the middle we

find the (interpeduncular fossa) see the picture below- If we make a line across the cerebral aqueduct the part behind it will be the tectum

(containing the inferior and superior colliculi )

and the part in front of it collectively known as the cerebral peduncle (which is dividedinto tegmentum and reticular formation)

- In front of the substantia nigra we can find the crus cerebri

- Behind the substantia nigra we find the lemnisci

- The red nucleus is NOT located between the substantia nigra and crus cerebri

NOTE : the lower part of this picture is the frontal part i.e. the crus cerebri is the

front & the tectum is the back , the Dr. said they may ask about the relations


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Important points:-

o The lamensci are located Behind of the substantia nigrao The Red nucleus is NOT located between the substantia Nigra and crus

cerebri.

o The part behind the cerebral aqueduct is the tectum containing thesuperior colliculus and the inferior colliculus.

o The part in front of the cerebral aqueduct is the cerebral pedunclecontaining the tegmentum ,reticular formation, substantia nigra.

o At the level of superior colliclus :o The same as in the level of the inferior colliculs regarding the cerebral

aqueduct,cephalic nucleus.

o There is nucleus of occulomotor nerve instead of the nucleus of Trochlearnerve (in the other level).

o Medial longitudinal fasiculus is present as in the level of the inferiorcolliculs.

o The Red nuclei (motor nuclei) are present.o The fibers that come out from the Red nuclei immediately cross to the

opposite side to form the Rubrospinal tract.

o the Rubrospinal tract facilitate the function of the flexors and inhibit thefunction of the extensors (thanks to god ...It is not that very influential).

o The vestibulospinal tract -opposite to rubrospinal- facilitate the functionof the extensors and inhibit the function of the flexors.

o If there is a lesion in Red nucleus the patient have tremors in his upperlimb in the opposite side.

o The middle three fifths (3/5) of the fibers of the crus cerebri containcorticospinal and corticonuclear fibers.

o The lateral one fifth (1/5) of the fibers of the crus cerebri contain theTempropontine (NON-frontopontine) fibers.

o The medial one fifth (1/5) of the fibers of the crus cerebri contain theFrontopontine fibers.


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Remember:

-the corticopontine fibers come from the cerebral cortex to the pontine nuclei

& are divided to :

A) Frontopontine fibers come from the frontal lobe to the pontine nuclei.

B) Tempropontine (also called :Temprooccipitoparietopontine) fibers contain

fibers from Temporal lobe, Occipital lobe and Parietal lobe.o If there is a lesion in the crus cerebri , the basis pontis or the pyramid

there will be contralateral spastic hemiplegia.

Because the course of the fibers is from the crus cerebri to the basepontines. And at base of the pons the fibers make the pyramid.

o If there is a lesion in the fibers going to the pontine nuclei the patienthave ataxia.

o The corticonuclear fibers in the mid brain go to all the motor nuclei belowthe forth ventricle (Trigeminal nerve motor nucleus, Abducent nerve

motor nucleus,Facial nerve motor nucleus, nucleus ambiguous and

Hypoglossal nerve motor nucleus).

The Facial nerve motor nucleus and Hypolgossal nerve motornucleus receive only from one side(which is the opposite side)

unlike the others.

So , A lesion at this level in these corticonuclear fibers there will belower facial paralysis on the opposite side and genuglossus muscle

paralysis on the opposite side(i.e. the tongue will deviate to the

opposite side).

The corneal reflex:-

o Definition: the eye blink when the cornea is touched.o The cornea is supplied by the nasociliary branch of the ophthalmic division

of the Trigeminal nerve.

Nasociliary branch ophthalmic division Trigeminal nerve main sensory nucleus of the Trigeminal nerve in the pons


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The cell bodies : in the Trigeminal ganglion.

The central fibers : go to the main sensory nucleus of trigeminalnerve in the pons (because this nucleus is responsible for light

touch & pressure )

Afferent sensory nerve : in the opthalmic Efferent motor nerve : in the facial. The medial longitudinal fasiculus connective fibers will connect this

nucleus with the motor nuclei of the facial nerve of both sides.

Fibers from facial nerve go to both eyes to make the orbicularisocculi contract

The visual pathway:-

- Optic nerve optic chiasma optic tractthalamuslateral geniculatebody.

- In the optic chiasma :o The nasal fibers cross to the opposite side.o The temporal fibers go to the same side.

- Before the optic tract reaches the lateral geniculate body it gives fibers to thesuperior colliculus.


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Cornea is supplied by nasocilliary branch of the opthalmic division of trigeminal nerve.

explanation:

1\ Afferent limb walk in ophthalmic

2\ cell bodies in trigeminal ganglia

3\ central nerve fibers go to main sensory nucleus of the trigeminal nerve in pons

4\ main sensory nucleus of the trigeminal nerve connect to the motor nuclei of facial

nerve of both sides through median longitudinal fasciculus.

5\ Facial nerve supply orbicularis occuli muscle.

Summary: snell page: 339

*opthalmic division afferent limb of the trigeminal nerve >to> sensory nucleus

of the trigeminal nerve >to>the motor nucleus of the facial nerve in both sides

throughmedial longitudinal fasciculus. Facial nerve and its branches efferent supply

the orbicularis occuli muscle.

note:

- main sensory nucleus is concerned with light touch and pressure.

- Spinal nucleus for pain and temperature.

- mesiancephalic nucleus in medbrain for proprioception .

visual pathways: snell page: 336

1\ optic nerve.

2\ optic chiasma: nasal fibers cross & temporal fibers go to the same side.

- Both nasal & temporal make the optic tract.

- Optic tract goes to the thalamus & end in the lateral geniculate body.

- Before ends it gives fibers to the superior coliculus &pretectal nucleus.


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importance ofsuperior coliculus & pretectal nucleus: snell page: 338- if we shine a light on one eye its pupil will constrict direct pupillary reflex.

- other eye pupil also will constrict. consensual pupillary reflex.

- both reflexes happen at the same time.

*reflexes mechanism:

1\ impulses goes through the optic tract from the lightened eye to thepretectal

nucleus which lies close to the superior coliculus.

2\ Then the impulses goes from the pretectal nucleus to the edinger-westphal

nuclei parasympathetic nucleus of the oculomotor nerve on both

sides.

(fibers cross the median plane to the other side throughposterior commissure.)

3\ finally, preganglionic parasympathetic goes (with the occulomotor) to ciliary

ganglion in the orbit and end there .

& postganglionic parasympathetic goes from the ganglion through short ciliary

nerves to the constrictor pupillae muscle & the ciliary muscles (ciliary body)

Summary of the mechanism:

light cause impulse > optic tract > superior coliculus > pretectal nucleus >

parasympathetic nuclei of both sides > preganglionic fibers > ciliary ganglion(here

preganglionic end) > postganglionic short ciliary nerve > ciliary body and constrictor

pupillae M. > produce constriction in both pupils.


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NOTE : this reflex is called ( pupillary light reflex )

-- Note: oculomotor nerve has 2 nuclei:

1\ Motor: supply levator palpebrae superioris and extra occular muscles.

2\ Parasympathetic edinger-westphal nucleus: supply ciliary muscle and constrictor

pupillae.

skin pupillary reflex: Snell page: 340

if you pinch someone's skin hardly his pupil will dilate.mydriasis

1\lateral spinothalamic tract carrying pain.

2\When it ascend it gives collateral to the lateral horn in the 1st thoracic segment,

which contains the fibers that goes to the sympathetic chain to reach the superior

cervical sympathetic ganglion.

3\ postganglionic fibers goes with internal carotid and ophthalmic and give long ciliary

nerve which dilate the pupil.

Summary:

pain fibers > lateral spinothalamic tract >collaterals at 1st

thoracic segment to the

lateral horn > preganglionic sympathetic fibers > superior ganglion(preganglionic end

here) > postganglionic fibers in the internal carotid plexus along with ophthalmic artery

> long ciliary nerve > goes transient through the ciliary ganglion > supply the dilated

pupil .

The doctor mentioned :

-posterior commisure

-auditory area

-cochlear nerve


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frontal eye felid

if: 1\ stimulated > both eyes deviated to opposite side

2\ there is a lesion > both eye deviated to the same side.

Accommodation reflex: Snell page: 338

needs 3 thing or changes:

1\Needs 2 medial recti to contract and 2 lateral recti to relax.

convergence of the eyes

2\lens become more convex (become thick or fat)

increase the focal length of the lens

3\pupil constrict to let the light enter to the maximum convexity point in the lens.

constriction of the pupil


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Accommodation reflex requires 3 things:

1- Convergence of the eyes:Ask the patient to follow your pen so the eyes will converge ,so the 2 medial

recti contract & the 2 lateral recti relax

2- Increase the focal length of the lens ; the lens becomes fatter:When you get closer to the eye ,the convexity of the lens increase to focus the

image that is close to the eye i.e. lenses become thicker

3- constriction of the pupils so that the light goes through the point of maximumconvexity :

The 3rd

change the pupil must constrict to put the light on the place of max.

Convexity of the lens

How does this happen ?

- fibers reach the visual cortex which in front of the calcrine sulcus. Fibers pathway:- from the eye in the optic tract to lateral geniculate reaching the visual cortex- From the visual cortex fibers go to the frontal eye field, that is located beside

the precentral gyrus (which controls the motor functions of the opposite half

of the body)

- from frontal eye field through the precentral gyrus we have corticonuclearfibers which go directly to motor nuclei of oculomotor nerve of both side and

edinger-westphal (parasympathetic nuclei) of both side.- so the oculomotor nerve make the 2 medial recti contract- And (fibers) to the parasympathetic nuclei of both side so short ciliary nerve

makes the lens fatter through ciliary muscle and to make the constrictor

pupillae work to constrict the pupil .


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Notice here :

- pupillary reflexes from the optic tract ; fibers go directly to pretectal nucleus (did NOT reach the lateral geniculate)

- And here the pertectal nucleus through the edinger-westphal makes thepupillary constriction.

- Here in the accommodation reflex the pretectal nucleus has nothing to dowith it.

- That Means pupillary constriction might happen without the fibers goingthrough the pretectal nucleus, why?

Because the corticonuclear fibers that came form the cerebral cortex went

directly to the oculomotor nerve nuclei without the intermediary (mediation)

of the pretectal nucleus

( in the accommodation reflex the pretectal nucleus has noting to do with it

and that constriction does not happen through it . It happens by

corticonuclear fibers that goes directly to oculomotor nerve nuclei)

- So

t

h

e

p

--


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- so the pupillary constriction; fibers from the optic tract moves the pretectalnucleus and the pretectal sends to theedinger-westphal of both sides then

the fibers go out reaching ciliary ganglion, where short ciliary make

constriction.

In the case of accommodation reflex the pretectal nucleus is not needed.directly from motor cortex, corticonuclear fibers go down to the edinger-

westphal & the motor nuclei of the oculomotor nerve producing the constriction

and the increase in length.

- The trochlear comes out of its nucleus and the medial longitudinal fasciculus

connects with both nerves .(I think both trochlear nerves)


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- How to test for the trochlear nerve ? trochlear nerve supply superior obliquemuscle (the superior oblique muscle will make the eye looks downwards and

laterally)

- so if the superior oblique muscle is paralyzed that effect the eye looks up ,and the patient will complain when he goes down the stairs of double vision

Diplopia because one of the eyes that looks downward and the other

cannot . now this how we test for trochlear nerve and this is what happenwhen we get a lesion of it.

- Abduscent nerve supplies lateral rectus i.e. moves the eye laterally- The oculomotor nerve supplies the superior rectus and the inferior rectus,

medial rectus and inferior oblique so it moves the eyes upwards and medially

and downwards.

- It also supplies the Levator palpebrae superioris muscle that left up theeyelids and it also supplies the constrictor pupillae.

- So if the oculomotor nerve is paralyzed there will be blepharoptosisdrooping of the upper eyelid

- (blepharoptosis is NOT confined to damage of the oculomotor nerve , forexample Horner's syndrome has blepharoptosis because part of the Levator

palpebrae superioris is smooth muscle and the other part is skeletal muscle .

The skeletal muscle is supplied by oculomotor nerve and the smooth muscle

is supplied by the sympathetic )

- So if we have Horner's syndrome or oculomotor nerve paralysis the patientwill have blepharoptosis

Q : how can we differentiate between these 2 cases of blepharoptosis ?

*Horner's syndrome : the sympathetic is damaged, so the parasympathetic

will take over and this patient will have :

1- blepharoptosis

2- miosis ( constriction of pupil)

3- anhidrosis and

4- enophthalmos .


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*oculomotor nerve lesion :the constrictor pupillae is damaged because it is

supplied by parasympathetic which is brought up by the oculomotor so the

sympathetic will take over . so in this case there will be :

1- blepharoptosis

2- mydriasis.

3- eye fixed downwards and laterally .

This patient only have lateral rectus (abducent) & superior oblique (trochlear)working , so hewill come to you with an eye that is fixed downward and

laterally he cannot left it up, down or any direction and of course he will have

diplopia.So in oculomotor nerve paralysis we see blepharoptosis , mydriasis

(dilated pupi) , and an eye which is fixed downwards and laterally where the

patient cannot move it upwards , medially or downwards .

The mid brain:

two syndromes :

1- Weber's syndrome:- involves the crus cerebri and the oculomotor nerve.- Curs cerebri has the middle 3/5 which includes the corticospinal and

corticonuclear, the medial 1/5 conclude frontopontine and the lateral 1/5 has

the non-frontopontine fibers .

- In Weber syndrome,corticospinal fibers are involved so there will be spasticparaplegia of the opposite half of the body.

- Spastic paraplegia in curs cerebri, in the basis pontis, in the pyramid all ofthese are conditions of paraplegia in the opposite side.

- in addition to paraplegia we have corticonuclear fibers going to supply thefacial and the hypoglossal . So ,the patient

will have contralateral spastic hemiplegia,

lower facial paralysis in the opposite side

and the tongue will deviate to the

opposite side.

- In addition to that , we havethe oculomotor nerve paralysis where

there will be blepharoptosis and mydriasis

and the eye ball fixed downward and

laterally.


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2- Benedikts syndrome:- Involves only (the oculomotor

nerve, red nucleus, and the medial lemniscus) .

- in case oculomotor nerve we said itbefore (blepharoptosis and mydriasis and the

eye ball fixed downward and laterally).

- In case of red nucleus:contralateral tremors of the upper limb.

- In case of medial lemniscus:contralateral loss of proprioception,

discriminative touch and vibration sense.

neuro anatomy toutrial[1]

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