UPPER VS LOWER MOTOR NEURON LESION,CENTRAL VS PERIPHERAL FACIAL PALSY,11&12CRANIAL NERVE PECULIARITY

0:00 [Music] hi everybody welcome to my youtube channel dr srinivas medical concepts and my fb page dr srinivas concepts this is dr srinivas neurologist from andhra pradesh india i am also the medical author of the book focused neurology today we will be talking about very very fundamental most basic and very very important topic the upper motor neuron lesion versus the lower motor neuron lesion central facial palsy versus peripheral facial palsy and the peculiar

0:46 innervation of 11th and 12th nerves so we'll start away with upper motor neuron versus lower motor neuron differences to understand the central facial palacy versus the peripheral facial palacy so the corticospinal tract the corticobulbar tract the pyramidal track this is primary responsible for the movements it is purely a mortar tract it has got nothing to do with sensory whatsoever so it's purely a mortar truck the pyramidal tract so if i need to perform any movement

1:31 then this pyramidal track comes into force but to understand this we need to understand a very important concept upper motor neuron and lower motor neurone so the cortico bulba and the corticospinal tract starts from the cortex distance to the internal capsule supplies all the cranial nerve nuclei comes to the anterior horn cells from the anterior cell what comes out is the peripheral now and from the cranial nerve nuclei what comes out is the cranial nerve so the upper motor neuron there are two two components

2:17 one the cortical bulbar fiber coming up to the motor part of the cranial nerve nuclei which is known as the cortico bulbar fibers and the perimeter coming up to the anterior consoles which is known as corticospinal tract so upper motor neuron has two components the cortical bulbar fibers coming from the cortex to the motor part of the cranial nerve nuclei and the corticospinal fibers coming from the cortex to the antioxidants of the spinal cord likewise we have two components in the lower motor neuron one what comes out from the cranial nerve nuclei as cranial now is lower motor neuron what comes from the anti-reform cell as

3:02 peripheral nervous lower motor neuron so lower motor neuron also there are two components one the cranial nerves and second the peripheral nose here we need to understand a very important concept the pyramidal tract is purely a mortar tract it has got nothing to do with sensory whatsoever so what do we mean by this it goes to the third nucleus fourth canadian now nucleus but fifth has got mortar so it goes only to the motor part of the fifth uk then it goes to the sixth now it goes a seventh now it does not go to the eighth round because eight no is purely a sensory now it does not go to the ninth now it goes to the tenth row eleventh now and

3:49 twelfth notes and then crosses over to the opposite side at the level of the middle oblong attack goes to the anterior answer so it goes only to the motor part of the cranial nerve nuclei another very important concept is that the cranial nerve nucleus are bilaterally innervated very important concept the cranial nerves are bilaterally innervated only if we understand this we can proceed further to understand stroke and the differences between the central facial policy versus the peripheral facial palsy so the cranial nerves all the cranial nerves are bilaterally innervated hence when there is a lesion on the right side when there is a lesion on the right side

4:34 there is left hemiplegia left upper limb and left lower lip but the cranial nose do not get affected because the cranial nose get bilateral innervation from the same side cortico bulbar truck and from the opposite corticobulbar tract also therefore if there's a lesion on the right side the other corticobulby fibers comes and supplies his cranial nerve and compensates and therefore cranial nerves are not involved in the person suffering from hemiplegia except the seventh cranial nerve so none of the cranial nerves are involved in a person having a um and lesion about the brainstem except the seventh noun why the seventh round i'll i'll talk in a while from now

5:21 so in a person who's got a lesion above the brain step example right side they have only left hemiplegia and though the cranial nerves three to twelve are affected they do not manifest because they got bilateral innervation not only for the same cortical bulbar fibers but also from the opposite corticobulbar fibers and therefore cranial nerves are not involved in a lesion which is above the brainstem except 7th now which i'll talk about in few minutes from now right now again coming back to the basics the upper motor neuron there are two components corticospinal fibers likewise lower motor neuron also there are two components nose and peripheral nose now let's see

6:07 what are the differences between upper mother neuron nation and lower motor neurone in upper motor neural nation the bulk is normal there may be some amount of disuse atrophy but by and large the bulk is normal but in the lower motor neuronation especially example the anterior horn cells there is simply a loss of bulk there is if we are wasting there in fact they are all bones example polio myelitis motor neuron disease when the anterior horn cells lower motor neuron is affected there is severe wasting of the muscles you see only bones severe wasting but no wasting or at best there will be minimal disuse wasting in upper motor neuron second in upper motor neuron lesion the tone is hypotonia

6:53 and increase in tone it could be spasticity or rigidity spasticities you see in um and lesions pyramidal tract lesions where the anti-gravity muscles are more effective that is flexors of the upper limb and extensors of the rholim and it is class knife spasticity injury it will be difficult then it will be easier to overcome whereas rigidity you see in extra parallel track lesions where both flexor groups and extensor groups are equally affected and it is lead pipe that is the tone that is it is equally difficult to open up so whatever maybe that is positivity originality there is hypertonia in a um addition whereas in in lm malaysia it is hypotonia the tone is decreased then the superficial reflexes

7:41 the superficial reflexes have got local pathway as well as another pathway coming from the cortical spinal tract and therefore superficial reflexes are absent both in um and lesion as well as an lmn lesion deep tendon reflexes the deep tendon reflexes are under constant inhibition by the corticospinal tract and therefore when there is a corticospinal tract lesion um and traction these reflexes get disinhibited and they get exaggerated so in a human region the deep tender reflexes are brisk and in lm lesions the deep technologies are absent and of course the most important sign of neurology the extensor plantar response or babinski is saying you see an upper motor neuron lesion

8:28 where the lesion is above s1 where if we elicit where we if we try to elicit the plantar reflex the big toe goes upwards then the other toe goes for fanning so extend some plantar response is seen in upper motor neuron lesions whereas in lower motor neuron agents either it is flexor or absent the power in upper motor neuron lesions only groups of muscles are affected groups of muscles are weak for example extensors of the upper limb and flexors of the lower limb are weak since extensors of the upper limb are weak but the tone in flexors are increased and since flexors of the lower limb are weak but extensor muscles of the tone there is an increased stone person will have a flexion of the upper limb and extension of the lower limb where it cannot flex the knee and

9:14 therefore he walks like this this is known as subconduction gait because he is not able to flex the knee to clear off the ground he has to encircle and then walk so you see characteristically patient walking like this with the flexion of the upper limb and extension of the lower element in cycling this is a very classic gate known as subconduction gate where you see in uam and lesions whereas in lm and lesions it is not the groove it is the individual muscles which are affected for example the c5 is affected biceps infraspinatus rom watch delta and supraspinatus are affected so in upper motor neuronation groups of muscles are affected whereas in whereas in lower motor neuronations individual muscles are affected in upper motor neurone issues you don't see fastic relations

9:59 but in lower motor neuron lesions you see pacifications involuntary muscle twitchings this is because of cannon's law of denervation super sensitivity when anterior horn cells are affected it becomes super sensitive to its chemical here acetylcholine for example the anterior hamster is affected it becomes super sensitive to australic and therefore even if there is no voluntary impulse coming involuntary the muscles will start twitching which is known as fasciculations because of cannon's law of denervation supersensitivity so you see fast equations in role mode on your own type but in upward motor neuron type it is absent so to put it in a very simple manner in a lesion which is above the brain stem there is hemiplegia on the opposite side

10:44 because the tract crosses the level of the middle of blood and goes to the opposite side but cranial nerves are not involved because cranial nerves are bilaterally innervated and therefore if my right corticosteroid gets affected there'll be only left amplitude but the cranial nerves on the right side are not affected because they get bilateral innervation except seventh round very very important why in seventh you know why only the seventh note gets affected in a lesion above brainstem this is the explanation the seventh row you can see it is in the pons now i have enlarged the nucleus of the seventh cranial nerve in the pons the seventh now nucleus is got upper part and the lower part the seventh nucleus got upper part and the lower part the phase you divide it equally into upper half and the lower

11:31 half the upper part of the nucleus supplies the upper part of the face the lower part of the nucleus supplies the lower part of the face fine now there is an upper part and the lower part of the facial nuclei like all the other cranial nerves the upper part of the facial non-nucleus has got bilateral innervation for example on the right side the right upper part of the facial nonsense suffered both by the as well right the left corticobulba fibers but the lower part gets supply only from the opposite side this is the peculiarity this is the uniqueness this is the cat that's why in a lesion above brainstem none of the cranial nerves are involved except 7th now so this is the explanation so the lower part of the facial non-nucleus has not got bilateral

12:16 inheritance like other cranial nerves it has got unilateral innervation and that too from the opposite side so what is upper mark on your knot anything above the nucleus is upper month on your own anything better than you resist lower motor neuron so in the upper motor neuron a central facial policy when there is a lesion the upper part the fibers the upper part this gets affected but is compensated by the left side finally only the lower part of the facial or nucleus on the opposite side gets affected lower part supply the lower part of the face and hence the lower part of the face only gets affected in right humidity so finally when there's a right euromandation only the lower part and that opposite side of the face gets affected so person who's got lesion above the brainstem on the right side example you'll have left hemiplegia and only

13:04 left lower part of the phase getting affected now we see element lm is the lower motor neuronation though so the final pathway is gone example builds pricing so when the final path is gone both the upper part and the lower part on the same side are affected so in lm elevation both the upper part and the lower part on the same side is affected whereas in a um lesion lower part on the opposite side is affected now let's try to find out the differences between the central facial passage that is upper motor neuron of healing and peripheral facial pressure that is a lower motor neuron of the facial law but before that i need to introduce a concept which is known as belt's phenomenon belt's phenomenon is a reflex up gaze with forceful eyelid closure

13:49 when i close my eyelids my eyeball goes upwards this is a normal phenomenon so bell's phenomenon is a reflex up gaze when there is a flows eye closure what is the mechanism the mechanism is that the levator palpably superioris and the superior vectors both supplied by the third node they are matched tone wise that means when the eye looks down both the tone of both the muscles are decreased but when the when a person looks upwards there is an inhibition of the levator parabolic superioris but excitation of superior rectus so bell's phenomenon is a normal reflex updates when there is a forced eyelid closure the levator pelvic brace superior which is responsible for the elevation of the eyelid and the superior rectus which is

14:35 responsible for the elevation of the eyelid the tone of these two muscles are matched they are equally matched when they look downwards so when they look downs they are they are match so downgrades they are both are inhibited since limited alcohol superior is inhibited the eyelid drops down since the superior rectus muscle is inhibited the eyeball goes downwards so when a person looks downwards both the levator pulverised superioris and the supererectus muscle are inhibited and therefore there is eyelid drooping and the eyeball comes down but when a person looks upwards the levator palpably superior is is inhibited that means eyelid drops but superior it is normal the tone is not

15:20 decreased it is increased and therefore the eyelid the eyeball moves upwards so when they look upwards the tone reverses there's an inversion of the tone so the linear tobacco resuperior is the tone decreases so eyelid falls down but the superior rectus the tone increases and therefore the eye ball moves upwards so this is bell's phenomenon when there's a forced eyelid closure it is a normal phenomenon when i ask anyone to close the eyelids when they close the eyelids i can see the eyeball moves upwards but i can't see in normal persons because they close the eyelids but in persons with base spell see when the upper part of the face is affected when they attempt to close the eyelids they cannot close the eyelids because the orbicularis occlus is affected but you can see the eye eyeball moving upwards

16:06 so based phenomenon is a normal person but well seen in persons with bell's palsy because they cannot close the eyelids but the moment they attempt to close the eyelids you can see this reflex getting manifested so now let's see what are the difference between upper motor neuron and lower motor neuron or central facial palacy from the peripheral facial policy the lesion is above the nucleus in the upper motor neuron the lesion is below the nucleus in the lower motor neuron when there is a when there is an upper motor neuron lesion the lower half of the phase gets affected when there is an element lesion both the upper part and the lower part on the same side gets affected in upper motor neuron nation the belt's phenomenon is not well seen because they can close the orbicularis operate but in an elementation the

16:51 bell's phenomenon is built in because they cannot close the eyelid because of the orbicularis off by weakness but the moment they attempt to close the eyelid you can see the eyeball moving upwards the corneal reflex is present in upper motor neuron lesions but the coronal reflex is absent in lower motor neuronation because the offering for the coronary reflexes is the ophthalmic division of the trigeminal nerve different is bilateral facial nose and therefore when the phase right now gets affected with sometimes the orbicular is applied the corneal difference is absent so a person who is having element facial nerve type of policy they'll have the cornea reflex being absent the facial reflexes like in the upper northern neuronation the reflections are pretty low amount of urination the facial the

17:36 reflex are absent so facial reflex is that water and works orbitals or play reflex we have to pinch the muscle between at the lateral canthus and then percuss it behind the towards the ear and you can see nice contraction of the muscle so the upper motor neuron type of facial patch your central facial policy the walking bugs arbitrage alkaline reflexes brisk whereas here it is normal or absent in an element facial palacy then as i said this pathway coming from the cortex to the pons you have a voluntary pathway for upper motor neuron or facial palacy you have an emotional pathway also coming the path is not well known but it can go through it's towards the cingulate garage or thalamus and then come to the

18:22 facial now nucleus so upper mother neuron or facial you have basically two components the supra nuclear path is one the voluntary component second is the emotional component so a person have may have only the voluntary component being affected whereas emotional component may be normal so when when you ask the person to claim city to open to show that teeth you can see nice flattening of the of the angle of the mouth and getting deviated towards the opposite side if you give a command but when he smiles automatically it may be normal so there is voluntary and emotional dissociation sometimes for example calming in fact when they smile the the facial pulse may be there but on voluntary command it may not be there

19:08 so supra nuclear facial pathway has got two components one the voluntary component second is an emotional component so both can be dissociated only the voluntary part can get affected wherein when you give a command you can see the facial palacy but when they smile automatically emotionally it may be normal on the other hand when they smile it may get affected but voluntary when you give command it may be normal so that could be a voluntary emotional dissociation in the human condition but in elementary both are affected right initially as for the sake of simplicity simplicity i said that the all the facial now all the cranial nerves are bilaterally innervated except seven but there are two pectoralis one for the eleventh no one for the twelfth novel

19:53 the eleventh now which supplies the sternocleidomastoid has got predominantly unilateral innervation so the cortex supplies the urine latter the ipc levels turn off keto mastoid and therefore when there is a right cortical lesion the sternocleidomastoid on the same side gets affected so it cannot turn the head towards opposite side the head will turn towards the same side so another peculiarity so generally the scheme is that the cranial nerves get better better innervation from the contralateral side but here the sternocleidomastoid which is supplied by the eleventh now has got more of its lateral contribution and therefore when there's a right-sided lesion the ifc lateral the same size for sternocleidomastoid muscle gets affected

20:39 so person cannot turn the head towards opposite side the head will be turned towards the side of the lesion and another important uh peculiarity or the exception is the genius losses supplied by the president genius losses of all the muscles has got predominantly contra lateral supply and therefore when my right cortex gets affected the left sided now supplying the genius losses gets affected gene your glasses pushes the tongue to the opposite side and since the genius losses muscles the nerve supply and get trafficked in the twelve gets emitted it is pushed towards pull towards the same set so the genius losses of the 12th now has got a predominant control electric supply the 11th now supplying the sternocleidomastoid has got the predominant

21:24 ipsilateral supply the seventh the upper part is got bilaterally narrated but the lower part gets predominant innervation from the contralateral side these are the peculiarities of the seventh note 11th november so this is a overview of the differences between upper modal neuronation and lower motor neuronation and general facial palsy and peripheral patient facial palsy and these are the peculiarities of the seventh or eleventh note and twelve i hope it was a very interesting lecture and you have understood the basics and enjoyed it i've enjoyed giving the lecture and i hope you have also enjoyed listening to my lecture if you have really liked the lecture please like and subscribe and post your comments on my youtube channel doctors invoice medical concepts and my fp page doctor's universe

22:10 concepts thank you bye