USMLE Step 1 Tutorial - Conjugate Gaze Explained

[@margaretprawl313]

Thank you Doc. I am a nursing student . My name is Junior. Needed something simple but efficient to help me in my nursing assessment of people with alcoholic toxicity as reflected in palsies of the eye. Your video lets me understand what I am looking for and why it happens. Wish I had you as a tutor in Nursing school.

[@ForeignDoc]

Very good but you should include in your diagram/explanation - the frontal eye field (broadmann area 8) and PPRF (you did mention reticular formation however)

[@chunkymonkey2782]

i still don't get what the PPRF does

[@muthuswamin1047]

The PPRF is the reticular formation he is talking about in the video.PPRF= Paramedian pontine reticular formation.To look to the left,the right frontal eye field sends impulses to the left paramedian reticular formation. The left PPRF sends impulses to left (ipsilateral) 6th nerve nucleus and it stimulates left lateral rectus causing abduction to left side.Simultaneously the 6th nerve nucleus sends impulses via right medial longitudinal fasciculus to right 3rd nerve nucleus.The right 3rd nerve nucleus innervates the right medial rectus causing adduction of the right eye.Therefore left eye abducts and right eye adducts resulting in horizontal gaze to the left.

[@diendamadick9184]

​@@muthuswamin1047 Bottom line: MLF lesion = no medial movement of ipsilateral eye, positive lateral movement of contralateral eye PPRF lesion = no lateral movement of ipsilateral eye, no medial movement of contralateral eye

[@blacktongs]

New favourite channel! Thank you!

[@oliversykez7292]

Wonderful explanation in a very short time! Thank you!

[@yztyzt1]

u r a god of explanation! Holy shiit ur good at the usmle! In fact, I am not even studying the USMLE. Instead, I am studying for the specialty boards of ABPN. And I am still using your vid to study the neuro section. u r a god.

[@homahealthcarecenter]

in gazepalsy, first rule is individual eye ball movements should be normal. first check single each eye seperately,then go for gaze movements

[@reuelpn]

Fantastic explanation ! Really appreciate it !

[@ATA-wi2lh]

can you do vertical conjugate gaze?

[@khalidthego]

Great video, Thank you so much

[@SteezySteez2011]

I've seen patients + for hemorrhagic stroke with conjugate gaze, is this a result of blood accumulating within the cranium, and applying pressure on CN6?

[@JOHNNIEUSA]

great video

[@positivevibes7425]

What is the role of Broddmann's 8 area in this pathway?

[@davebuikema4119]

That ignites this pathway. It is the initiator. Broddmann's 8 is also known as the FEF. Frontal Eye Field. The FEF (Brodman 8) on the Right sends impulse to the PPRF (reticular formation) on the Left. To recap: R FEF --> L PPRF. L PPRF sends impulse to L Abducens Nucleus (CN 6 Nuc). This does NOT cross! So to recap: R FEF --> L PPRF --> L CN6 Nuc. L CN6 Nuc innervates L Lateral Rectus. L CN6 Also sends an impulse via the R MLF to the R CN3 Nucleus. To recap: L CN6 --> L lat. rectus and R MLF. R MLF carries to R CN3 Nuc. R CN3 Nuc innervates R Medial Rectus. Once you understand this you can kind of rationalize what the symptoms would be based on the location of the lesion. Another useful thing to note: If the nucleus or the nerve itself is damaged, the associated muscle will atrophy! So if the patients R lateral rectus is atrophied, you can consider the R CN6 and its nucleus to be lesioned. This is useful for differentiating between scenarios where the only difference between "scenario 1" and "scenario 2" is an atrophic condition of the muscle. Hope this helps!

[@btirador]

very concise and helpful. thank you!

[@moathalmosa3918]

Thanks a lot, your explanations were really helpful.

[@mandanamashoof3015]

Thanks for the great explanation.

[@mohammadhamadneh3611]

Incredible video

[@siddharthakancharla1954]

Thanks ... It was very help full

[@Ani.DR.07]

crystal clear concept s . thanks

[@barrythompson1122]

Excellent explanation

[@89tees]

Thanks for this sweet video!

[@robbiedart7422]

But why does the left CN6 control the left eye and vise versa? I thought each hemisphere controls the contralateral eye?

[@miizayesu]

This doesn't apply in the case of cranial nerves. That would be in the case of corticospinal, corticobulbar and other sensory/motor tracts I believe

[@robbiedart7422]

miizayesu wow that was a dumb question what was I thinking haha, the effects of too much neuro on the brain... cheers tho

[@omidmushtaq4768]

what abt PPRF and Frontal eye field

[@Bradatimrkonja]

+Omid Mushtaq I think PPRF and FEF are located ipsilateral to the effector ncl. VI ?

[@AsifKhan-fh2om]

Awesome ..

[@oksanajames7960]

Thank you so much !!

[@gunabharathi3152]

Why opposite side nystagmus formed?

[@Michael44413]

Thank you

[@jayvanithakurgarcia9386]

very clear!

[@bman3800bman3800]

What is this for?

[@achinisamaranayake8546]

Thank you!

[@RobinahJuru1992]

Thanks heaps for this :)

[@joyoluchukwu6397]

thanks

[@lailalu8714]

Best

[@nomankhallid]

Thank you so much.