 Hello everyone, welcome to the session on the brainstem. In this session we will be quickly revising all the components of the brainstem ok. So, which all are the parts of the brainstem? Here we can see the image of the brainstem viewed from the anterior aspect. So, this cranial most part of the brainstem this is the mid brain and this middle part this is the font and the lower part of the brainstem this is the medulla oblong data ok which will continue as the final code below ok. So, in this session I will be covering all the three parts of the brainstem under these standard headings the external features of that part the internal features as well as the applied anatomy ok. External features of all the three parts of the brainstem I will cover together and internal features we will see one by one along with the applied anatomy ok. So, let us begin with the external features here we can see the brainstem viewed from the anterior aspect, brainstem viewed from the posterior aspect ok. So, we will cover external features from below upwards. So, here this is the medulla oblong data viewed from the anterior aspect the anterior most structure here which is seen this is the anterior median fissure ok and just lateral to it this structure is the pyramids ok. Just lateral to it there is an elevation which is referred to as olive and lateral to it there is inferior cerebellar peduncle ok. And in between the pyramids and the olives this groove which we can see this is the anterolateral sulcus and between the olives and the inferior cerebellar peduncle there is posterolateral sulcus ok. And this anterior median fissure when meter is upwards there is a small depression here this is the foramen teacum ok. So, these are all the features in the anterior aspect of medulla oblong data. Let us see the features along the posterior aspect of medulla oblong data. If we see the posterior aspect we will observe that the lower part of the medulla oblong data is a closed part and the upper part of medulla oblong data is a open part ok. The features of the closed part which has been on the posterior aspect have this elevation is the gracile tubercle and just lateral to it there is cuneate tubercle ok. And in the open part it is actually a part of the fourth ventricle ok. So, when you study the external features of the posterior aspect of ponds and the medulla oblong data. So, most of the structures are included in the floor of the fourth ventricle ok that we will be covering later on. The demarcation between ponds and medulla oblong data is by wide band of fibers which will be visible here those are referred to as straya medulla iris ok below it is medulla oblong data above it is ponds. And let us see the features of the ponds along the anterior aspect. So, there will be transverse striations which will be seen because of the transversely running ponto cerebellar fibers ok. And this on the lateral aspect there is middle cerebellar peduncle ok junction between the ponds and middle cerebellar peduncle there is a nerve which exits from the ponds that is the triseminal nerve ok. Then along the midline has a shallow groove which is referred to as bezilar groove which lodges the bezilar artery ok. Then midbrain on the anterior aspect here we can see the cerebral peduncle ok on each side. Then midbrain seen from the posterior aspect there are four rounded elevations. These four rounded elevations to the upper two are referred to as superior colliculus lower two are referred to as inferior colliculus ok. And all four together are referred to as corpore or cordary germina ok. Then separating this colliculus there is a cruciform sulcus ok like a cross as a cruciform sulcus which separates this four colliculus. Then we trace this vertical limb of the cruciform sulcus upwards will reach towards the pineal gland and then we trace it downwards will reach towards the superior medullary vealum which comes the roof of the fourth ventricle ok. These are all the features along the posterior aspect of midbrain ok. And when we study about the brain stem the study of attachments of the cranial nerves are also important in all there are 12 pairs of the cranial nerves out of which 10 pairs of the cranial nerves they are attached along the brain stem ok. So, which 10 the third and the fourth cranial now they are related with the midbrain. Fifth cranial nerve as we discussed the triseminal nerve then sixth, seventh and eighth. These three cranial nerves are at the pontometallary junction along the medial aspect there is sixth now that is the adducent nerve and seventh and the eighth the facial and the vestibulococcal nerve they are along the lateral aspect of pontometallary junction ok. Then the last four cranial nerves 9, 10, 11, 12 these two cranial nerves are related with the medulla oblong data. On the anterolateral sulcus there will be attachment of the 12th nerve hypoglossal nerve and posterior lateral sulcus will give attachment to this remaining three nerves 9, 9, 10 and the 11th cranial nerve ok. So, 12th nerve along anterolateral sulcus 9, 10, 10, 11th nerve along the posterior lateral sulcus ok. So, with this basic idea let us cover the internal features of the brain stem. So, while studying the internal features there are seven sections of the brain stem which we need to study out of which three sections are in the medulla oblong data two sections are in the ponts and remaining two sections are in the midbrain ok. So, we will study one by one and we will study below upwards ok. First we will study the lower most section of the medulla oblong data and lastly we will go up to the section at the superior colloquial of the midbrain ok. So, let us start with the section of medulla oblong data at this lower level. This lower level is at the level of pyramidal decussation ok. There is there are decussation of the pyramid and there is a level just above it there is sensory decussation and there is one level at the level of the olives ok. So, three sections we need to study in medulla oblong data. Let us start with the first section. So, here this image shows the section of the medulla oblong data at pyramidal decussation ok. So, when we say pyramidal decussation we will have to show decussation of the pyramids in this section ok. So, what do we mean by decussation of pyramids? Here we can see the white matter fibres pyramids which are on the anterior aspect. They are crossing ok. So, this crossing we will have to show in this section and after crossing they continue as the lateral corticospinal tract ok. About 75 percent of the fibres they cross ok and the remaining they continue as the anterior corticospinal tract. And while studying this section this section will look similar to that of the section of the spinal cord ok. So, the spinal cord if we take section at the cervical level this will look similar to this section. So, here we can see the central gray matter the peripheral white matter ok. So, in the central gray matter there is nucleus gracilis nucleus cuneatus and lateral to it there is spinal nucleus and tract of the trisominal nerve ok. Then this gray matter is separated from the central gray matter by this decussation of the pyramids ok. This is the detached anterior horn which is seen ok. Then apart from that which all structures are seen in the white matter these two yellow colored structures these are the phyno cerebellar tract going towards the cerebellum. Then there is lateral phyno thalamic tract ok. And these are the reticular formation which extends throughout the brain strength ok. So, few structures you will find in all the sections and there will be some specific structures with respect to that section. So, that is must when you draw a diagram at that particular level ok. So, it was section at pyramidal decussion let us try to recollect the various structures in an unlabeled image. Here we can see an unlabeled image section at pyramidal decussion. So, as per the name first we have to draw the pyramids then show the decussation of the pyramids. And because of this decussation the central gray matter is separate the anterior horn ok. This is the detached anterior horn the remaining part of the gray matter is nucleus gracilis nucleus cuneatus and final nucleus and tract of the triseminal nerve ok. Then in the white matter this is lateral corticospinal tract and these two are the phyno cerebellar tract and this is phyno thalamic tract the lateral phyno thalamic tract and this is the reticular formation ok. So, all these structures are important in section at pyramidal decussion. Now, let us cover the section at the sensory decussation. So, again we will have to show decussation of the sensory fibers with sensory fibers. Here we can see a fasciculous gracilis and fasciculous cuneatus they end in this nucleus nucleus gracilis and nucleus cuneatus and from there the internal arcuate fibers they cross and they after crossing it will ascend upwards as the medial lamnuscus ok. So, this crossing over of the fibers we will have to show and this crossing is in such a way that the medial fibers are related along the anterior aspect of the medial lamnuscus and the lateral fibers are along the posterior aspect of the medial lamnuscus ok. The medial fibers they represent the fibers of the lower limb ok. So, the lower limb is represented along the anterior aspect of the medial lamnuscus ok. Then the gray matter it is not seen as clear as that of the previous section the various nuclei are separated. These two nuclei we have already seen and this nucleus was also seen in the previous section spinal nucleus and tract of triseminal nerve and these things are also common. These things which are common I would not repeat it much. So, spinal cerebellar tract, spinal salamic tract ok and reticular formation is also common. Then along with the nucleus cuneatus that is small nucleus is referred to as accessory cuneate nucleus ok. In the fluorophore ventricle there is a structure called as stria medullary site. So, fibers of those arise from this accessory cuneate nucleus ok. Then along the anterior part this is pyramid and a small portion of this inferior olivary nucleus is also seen, but major portion of this will be seen in the section which is higher up that that is section at the level of olives ok. Then apart from that in the central gray matter the important nuclei are seen. This nuclei is this is the hypoglossal nucleus then dorsal nucleus of vagus and nucleus of practice solitaire ok. The central gray matter these three nuclei should be shown ok. Hypoglossal, dorsal nucleus of vagus and nucleus of practice solitaire. The central opening is the central canal of the medulla oblongata. It is actually the central canal of final cord which extends upwards ok. And this pink colored structure which is seen this is the medial longitudinal vesiculus ok. As this structure connects the third, fourth, sixth, eighth and eleventh cranial nerve ok. The third, fourth and sixth cranial nerve they are responsible for the eye movement. Eighth cranial nerve is responsible for hearing and balance and eleventh cranial nerve is responsible for neck movement through the sternocleidomastoid muscles ok. So, this medial longitudinal vesiculus helps in coordinating the actions of these five nerves ok. So, let us quickly recap this section in an unlabeled image ok. So, this section is at the sensory decursion. So, in this section we will have to show the decursion of the sensory fibers. So, these are the internal archivate fibers arising from nucleus gracilis nucleus cuneatus there is accessory cuneate nucleus and final nucleus and tract of the triseminal nerve, finocerebellar tract, lateral spinothalamic tract, reticular formation ok. This is the medial lemnus cis, some part of inferior olivary nucleus. Pink colored structure is the medial longitudinal vesiculus and three nuclei are seen in the central gray matter. From medial to lateral these are hypoglossal nucleus, dorsal nucleus of babies and nucleus of practice solitarius ok. Let us cover the next section now. So, this section is at the level of olives. So, here we will have to show the interior olivary nucleus very clearly ok. And just adjacent to interior olivary nucleus there are few other nucleus as well dorsal accessory olivary nucleus, medial accessory olivary nucleus ok. Then the three nuclei which we saw in the central gray matter in the previous section they are spread out in this section. This is the hypoglossal nucleus, dorsal nucleus of vagus, nucleus of practice solitarius ok. All these three nuclei we saw in the previous section as well and this lateral to it there is vestibular nucleus ok. Then few other nuclei the nucleus ambiguous, then final nucleus and practice trisominal nerve ok. And the three structures shown near the midline labeled as 1, 2, 3, 1 is the medial longitudinal vesiculus which we saw in the previous section as well. There is tectospinal tract and medial lemniscus ok. And here we can see the formation of vagus nerve as well ok. And this section is very important as far as applied anatomy of medial oblongata is concerned because if there is a vascular lesion of medial oblongata involving this area ok I will just shade this area to show you. So, if there is a vascular lesion it will involve the involve all these structures ok. One structure we missed this structure is the inferior cerebellar peduncle ok. So, whenever there is a vascular lesion in this area. So, all these structures we should know that these structures are present the dorsal nucleus of vagus, practice solitarius, final nucleus and trisominal nerve ok. Depending upon the structures involved we will be able to tell about the clinical features in that particular condition ok. And similarly there is one clinical condition which involves this medial area. So, if medial area is involved so what all structures are affected we should know and depending upon that clinical features we will be able to tell ok. So, let us first quickly revise the this section in an unlabeled image. So, this section is at the level of olive. So, we will have to show the inferior olivary nucleus and there is an accessory nucleus as well. And these three nuclei which was seen in the previous section as well, hypoglossal nucleus, dorsal nucleus of vagus, nucleus of practice solitarius, spinal nucleus and tract of the trisominal nerve. This is the vestibular nuclei, the nucleus ambiguous. The nucleus ambiguous is nucleus for the 9th, 10th and the 11th cranial nerve ok. Yellow color is the spinal cerebellar tract, green color is the lateral spinal thalamus tract ok. And these 1, 2, 3 labeled are medial longitudinal tessiculus, tectospinal tract and the medial lemnus this ok. And these are the pyramids just in front of the pyramid there is small gray matter that is referred to as arcuate nucleus ok. Now, with this basic ideal let us cover the applied anatomy of medial oblongata. So, as I told you there is one clinical condition which involves this posterior lateral aspect and one clinical condition involves the medial aspect ok. We will see one by one. So, here we can see the lateral medullary syndrome which involves the posterior lateral aspect of the medullo oblongata. This is also referred to as Boilenberg syndrome. The blood vessel affected here is the posterior inferior cerebellar artery ok. So, which all structures are affected here? Finothalamic tract if it gets affected it will lead to contralateral loss of pain and temperature in the front and the limbs ok. Then, final nucleus and tract of the trigeminal nerve if it gets involved it will lead to xylateral loss of pain and temperature over the face. While telling about the clinical features in the brain stem we should always think about which side is affected. For example, the opposite side is affected the word will be contralateral, same side is affected the word will be xylateral ok. Then, nucleus ambiguous but gets involved it will lead to xylateral paralysis of muscles of palate, sparing and larynx ok. Why? Because this is the nucleus for 9, 10 and the 11th cranial nerve ok. Then, inferior cerebellar peduncle which gets affected will lead to xylateral attack via the vestibular nuclei. Afection will lead to gidiness ok. This was all about lateral medullary syndrome. Then, let us see the medial medullary syndrome also referred to as gerin anterior bulbar syndrome. Artery involved here is the anterior spinal artery. Then, various structures affected. The pyramid here we can see the pyramid which is affected. Then, there are two other structures which are affected one is the hypoglossal nerve which will lead to xylateral paralysis of the tongue and medial lemnus will lead to contralateral loss of position and vibration sense ok. And pyramid if it gets affected it will lead to contralateral hemiplegia ok. So, this was all about the two syndromes. There are few more applied anatomy with respect to medullary oblongata that also will cover. One is the injury to the medullary oblongata. It is fatal because there are many vital centers in the medullary oblongata like cardiac center, respiratory center ok. Then, there is something called as bulbar palsy. In bulbar palsy the last four cranial nerves are affected. Why it is called as bulbar palsy? Because medullary oblongata is also referred to as bulb ok. It is shaped it is shaped is like a bulb. So, that is why it is also referred to as bulbar palsy. And there is one tumor in relation with the medullary oblongata called as medullary blastoma. It is actually a tumor of the cerebellar vermice which compresses along the vital centers of the medullary oblongata ok. This was all about medullary oblongata. Let us move on to the pons now. The pons also two sections will be covering one at the lower level one at the upper level. We will see the names of each of them and various features. The section at the lower level is referred to as section at facial colliculus ok. So, here we will have to show the facial colliculus in this section. And facial colliculus is formed by this nucleus of the abducent nerve as well as the winding of the facial nerve ok. So, these two structures we will have to show here. Then apart from that the vestibular nuclei is seen then cochlear nuclei is seen ok. And in general if you see the section of the pons this up to this part this is the segmental part and this part is the basilar part of the pons ok. Here we can see this is the medial lemnus disk then spinal lemnus disk and spinal nucleus and tract of the trigeminal nerve. And this is the trapezoid body ok. And in the basilar part there are longitudinal bundles of cortico nuclear and cortico spinal fibres. Contine nuclei and transversely arranged fibres are the transverse quantum cerebellar fibres ok. When this MTR is common from the previous section the medial longitudinal spectro spinal tract and reticulo spinal tract ok. And there is inferior cerebellar peduncle as well. Let us try to identify the various structures in an unlabeled image. So, here we can see the facial colliculus has to be shown here. Then nucleus of abducent nerve, facial nerve, then MTR that is the medial longitudinal septiculus, spectro spinal tract and reticulo spinal tract. And there is vestibular nuclei and cochlear nuclei ok. This is medial lemnus disk, spinal lemnus disk and spinal nucleus and tract of the trigeminal nerve in the trapezoid body. Cortico nuclear and cortico spinal fibres, then pontine nuclei, transverse quantum cerebellar fibres ok and inferior cerebellar peduncle. So, all these structures are seen ok. And as far as applied anatomy of faunce is concerned this section is very important because just like in medial oblong data we learnt with respect to the specific area there are clinical features. Similarly for this section is also important we will see the applied anatomy later on. Before that first cover the section at the trigeminal nucleus. So, this section shows the main sensory nucleus of the trigeminal nerve. Trigeminal nerve is actually a huge nucleus having part in the midbrain as well, part in the pons as well and part in the medial oblong data as well ok. This section shows the sensory nucleus and sensory as well as the motor nucleus both nuclei are seen here and in between them there is mesenchymalic root of the trigeminal nerve as well ok. And this we have already covered and these four lamnus chi are seen the medial trigeminal spinal and lateral. So, medial to lateral you can remember as m t s l and while thinking about the lamnus chi the functions of each lamnus chi should be knowing medial lamnus chi as we all know carries fibers of particular gracilis tunitis. So, is responsible for two point discrimination, vibration, position sense ok. Trigeminal lamnus chi carries pain and temperature of the face region. Final lamnus chi carries pain and temperature of the body and the limbs and lateral lamnus chi that is a part of auditory pathway. So, functions of all four lamnus chi we should know. Then this part is common from the previous section and this is the middle cerebellar peduncle and superior cerebellar peduncles are seen in this section and this is the cavity of the fourth ventricle ok. This covered by the roof that is the superior medullary vealum ok. So, all these things are seen in this particular section. Let us again try to recap in an unlabeled image. So, the all four lamnus chi we will have to show in this section. Then trigeminal norm nucleus, the motor nucleus, sensory nucleus and mesentipalic root we will have to show in this section ok. And middle cerebellar peduncle, superior cerebellar peduncle and middle longitudinal teticulus, tectospinal tract, reticulus final tract, small part of trapezoid body is also seen ok and this is the basilar part of the font. So, all these features are in the section and the upper part of the font. Let us cover the applied anatomy related to the font. So, as I told you there is an area which is involved here in this syndrome called as Millard-Gubbler syndrome. And posterior lateral aspect is affected in Montos cerebellar angle syndrome ok. We will see the cause and the clinical features. Millard-Gubbler syndrome in this, the artery involved is basilar artery ok. Basilar artery will supply this region right. So, this is affected, the abducent nerve is affected which will lead to axial lateral medial squint ok. Abducent nerve supplies the lateral rectus muscle. So, if it gets paralyzed. So, the eye will move medially. So, that is axial lateral medial squint. Involvement of facial nerve will lead to axial lateral lower motor neuron type of facial palsy. Then corticose final tract involvement will lead to contralateral hemiplegia ok. Then, Montos cerebellar angle syndrome. This is not due to any blood vessels, this is due to pressure on the ponds by acoustic neuromartic tumor in that region. If it compresses upon the ponds, it will lead to these clinical features. So, the compression of this nerve, eight cranial nerve, the facial nerve, we know at the pontometallary junction along the lateral aspect there are seventh and the eighth cranial nerve ok. So, if that gets compressed, it will lead to corresponding clinical features. So, vestibular cochlear nerve if it gets compressed, it will lead to tenetal progressive deafness and vertigo ok. Facial nerve, epithelateral lower motor neuron type of facial palsy. Cerebellar peduncle, compression leads to epithelateral otagria and staggering gait. Then, final nucleus and tract of trigeminal nerve is involved here that will lead to epithelateral loss of pain and temperature of the face ok. This was all about Montos cerebellar angle syndrome. Two other applied anatomy with respect to ponds, one is montane hemorrhage when there is bleeding inside the ponds, it will lead to pinpoint pupil, hyper pyrroxia, deep coma, then bilateral paralysis of face and limbs is a very serious condition. And tumors of the ponds astrocytoma is one of the noted tumors. And there are two other syndromes with respect to ponds, one is foveal syndrome in which the dorsomedial ponds is affected. So, in the dorsomedial ponds, there is adjacent nerve nucleus, spatial nerve nucleus. So, clinical features will be according to that. Rayman syndrome is basal pontine muscular legion, it is similar to that of the Millard-Gubbler syndrome ok. Now, let us cover the midbrain. The midbrain also there are two sections, one at the level of inferior colliequilus and one at the level of superior colliequilus, we will see one by one. So, before studying the sections proper, let us have a brief overview of how a section of the midbrain looks like. In general, we can say there are two parts in the section, one is the tectum and other is the cerebral peduncle and this demarcation is at the level of cerebral aqueduct also called as aqueduct of sylvia. So, in front of it there is cerebral peduncle which further has got three parts, the tegmentum, substancia nigra and the crust cerebrine. So, the dark color such as this is the substancia nigra, in front of it there is crust cerebrine and this entire area is the tegmentum ok. Let us cover the section at the inferior colliequilus. The name itself suggests inferior colliequilus that means, so you will have to show inferior colliequilus in this section ok. Apart from that this nerve has to be shown, prochlear nerve. Prochlear nerve is shown at the section of inferior colliequilus, oculomotor nerve is shown at the section of superior colliequilus, this difference we should know ok. And this all four lemnisci which we saw in the previous section, so that all four lemnisci are seen on this MTR we have already covered. Then in the central gray matter there is prochlear nerve nucleus and mesenchepalic nucleus of the prisminal nerve ok. Remember about the prisminal nerve I told you it has components in midbrain, pons as well as medulla oblong data ok, that is why it is seen here. This opening is the cerebral aqueduct and there is a decussation of the superior cerebellar peduncles which has been here. Then the black colored structure is a substantial nigra and this is the crust cerebrate which is having various fibres. Along the lateral aspect you can remember the fibres as POT ok, parietopontine, obstetrotopontine and tempuropontine fibres P O that is easy to remember. Then along the medial aspect there is only one type of fibres that is the frontopontine fibres. Then intermediate part, this intermediate part is the last part, two-third part ok, the lateral medial are one-sixth and one-sixth. Intermediate part there is corticoneuclear fibres, corticospinal fibres of the pyramidal tractor ok. So, it was all about this section, let us quickly recap in an unlabeled image. So, section at interior folliculus we will have to show interior folliculus then the prochlear nerve it is actually crossing over before it exists from the midbrain. That is the only nerve which exists from the dorsal aspect of the brain stem ok, all of the cranial nerves they are existing from the ventral aspect of the brain stem. Then the pore lamina sky MTSL as you can see here, this is the reticular formation and MTR we have already covered. This is the decussation of superior cerebellar peduncle and this is the substantia nigra in the crust cerebellar showing three parts and fibres ok. Let us cover the section at superior folliculus all right. So, superior folliculus we will have to show the superior folliculus as well as there are few other key pieces to be shown in this section. One is the red nucleus another is the oculomotar nerve ok. In the previous section we show we had shown the prochlear nerve in this section we will be showing the oculomotar nerve ok. Then in the lamina sky only three lamina stress is seen the lateral lamina stress is not seen why it is not seen because it has relayed into the inferior folliculus see because the lateral lamina stress is a part of voluntary pathway. So, those fibres has been through the inferior folliculus so that is why it is not seen in this section ok. Then mesenchipalic nucleus of trigeminal nerve is common it is seen in the previous section as well and this part is also common the crust cerebris substantia nigra ok. Then there are two decursions which are shown the ventral tegmental decursion of quarrel and the dorsal tegmental decursion of mean utter ok. And for applied anatomy of this midbrain this section is very important we should know that which structures are in the tegmentum of the midbrain. So, depending upon the structures will be able to tell about the clinical features of the patient. So, let us cover the applied anatomy before that first quickly recap the unlabeled image. So, this shows the superior folliculus in the red nucleus oculomotar nerve these three are the main things which should be shown then the three lamina sky medial trigeminal spinal then this nucleus is the oculomotar nerve nucleus this is the mesenchipalic nucleus of trigeminal nerve and there is a small nucleus which is shown here as the pre tectal nucleus ok. And this is the reticula formation and these are the two decursions ventral tegmental decursion dorsal tegmental decursion. Then this truss cerebrae and for extension this was covered previously. Let us cover the applied anatomy of the midbrain just like I told you specific areas we should know which structures are in the tegmentum of the midbrain and which structures are in the anterior medial aspect ok. So, this area is involved in Bieber syndrome this area is involved in Benedict syndrome and there is one syndrome called as Perinoid syndrome which involves the colliculus of the midbrain ok. Involvement of this area causes abnormal gaze ok. These two syndromes will study in details. So, Bieber syndrome that is caused due to the branch of the posterior cerebral artery. So, here we can see the area which is affected. So, corticospinal tract will be affected. So, that will lead to contralateral hemiplegia. Here you can see the oculomotor nerve as well. So, it will lead to ipsilateral lateral squint ok. Then Benedict syndrome caused due to the paramedic penetrating branches of the basilar artery ok because the penetrating branches will involve this area that area the tegmentum of the midbrain. So, which structures are there? Thread nucleus if it gets involved it will lead to contralateral force tremors. Then involvement of oculomotor nerve is common in Benedict syndrome as well in Bieber syndrome as well. So, then involvement of medial lemnisters it will lead to contralateral loss of position and vibrations in ok. So, this was all about the three parts of the brainstem with external features internal features and applied anatomy. So, for PDF handout you all can WhatsApp me at this number and please do watch the other sessions of this YouTube channel.