 Good day everybody. Dr. Sajja Sanyal, Professor Department Chair. This is another video demonstration of the intracranial venous sinuses. This is a composite view of many of the intracranial venous sinuses. On the left side, I'm holding up a base of skull where we have put by means of colored twine. We have put the location of the sinuses and this another base of the skull model which has got the pictures of the venous sinuses. It's just to give you a quick update. This is the sphenoperated sinus shown on both. This is the cavernous sinus on either side of the sphenoid bone, cavernous sinus. This is the superior petrocell sinus running on the ridge of the spherous bone, that is the superior petrocell sinus. This is the inferior petrocell sinus, inferior petrocell sinus which goes through the jugular for MN. This is the conference of sinuses, the conference of sinuses. So this is the termination of the superior sagittal sinus. This is the occipital sinus and we can see a little bit of the occipital sinus here. This is the transverse sinus also referred to as lateral sinus, continuing as the sigmoid sinus on this side and this side. So these are the composite view of the sinuses that I wanted to show you in both the models. This time we're going to focus on the conference of sinuses, the transverse, the lateral sinus and the sigmoid sinus. So I'm holding up the base of the skull in front of me. This is the anterior cranial fossa, this is the middle cranial fossa, this is the cerebellar fossa which is below the tentorium cerebelli. So let's focus on this region where my instrument is pointing right now. This is called the internal occipital protuberance and in this region there is a meeting point of five intracranial venous sinuses and therefore that region is referred to as the confluence of sinuses, also referred in Latin as torcular herofili. This same thing we can see in this sagittal view, this is the location of the confluence of sinuses, the torcular herofili and we can see the same thing in this view also. This is the location of the torcular herofili. What are the sinuses which open to the torcular herofili? First of all we have the superior sagittal sinus and that is seen here. This ends in the confluence of sinuses. Then we have a sinus which runs like this in the fax cerebelli and that is referred to as occipital sinus and a little bit of that is shown by this model here. That occipital sinus also opens into the confluence of sinuses. Then we have this sinus, this is the straight sinus which also opens into the confluence of sinuses. How is the straight sinus formed? The straight sinus is formed by the union of inferior sagittal sinus and the great cerebral vein of gallin, the two of them unite to form the straight sinus which then opens into the confluence of sinuses. The straight sinus runs at the junction between the fax cerebri and the tenturium cerebelli. So we have seen three sinuses opening into the confluence of sinuses and draining out from the confluence of sinuses on the right side we have this and the left side we have this. This is the transverse sinus continuing as the sigmoid sinus and that also referred to as the lateral sinus continuing as the sigmoid sinus. Generally it is said that the superior sagittal vein which I showed here this drains more of its blood into the right side and the rest of the venous blood goes more on the left side. The transverse sinus it runs in this groove on the inner surface of the occipital bone. This is the posterior attached margin of the tenturium cerebelli which forms a groove over the cerebellar fossa and the cerebellum is located below which also rains into this sinus. In this region it makes an S-shaped bend. This place is referred to as the sigmoid sinus because it is like an S in Greek it is sigma and after that the sigmoid sinus then goes out through the jugular foramen and here it is accompanied by cranial nums number 9, 10 and 11 and the infiripetrusal sinus and thereafter the sigmoid sinus continues as the internal jugular vein on both the sides. So this is the full course of the transverse sinus and the sigmoid sinus. Now let's take a look at some of the veins which drain into the stainless sinus and the sigmoid sinus. The sigmoid sinus receives labyrinthine veins which come out through the internal auditory meters and they drain the internal ear and they drain into the sigmoid sinus. What about the transverse sinus? The transverse sinus receives superior pitrusal sinus and we can see that here. I'm going to lift up this model of the brain here. There is a series of veins which run like this. They are referred to as the inferior cerebral veins which drain into the transverse sinus and additionally there's one large vein which connects the superficial middle cerebral vein in the lateral fissure of sylvia to the transverse sinus and that is referred to as the inferior anastomotic vein of lab. That also drains into the transverse sinus. Having mentioned these, now let's take a look at some important clinical correlations pertaining to the transverse and the sigmoid sinus. The transverse and the sigmoid sinus can undergo thrombosis especially in children in two conditions. One of that is otitis media, chronic superior otitis media and other is mastoiditis. Both of them are related continuum of the same manifestation. If you look at the other side of the skull we can see this is the mastoid process and this is the region where we have the mastoid anterum and the mastoid air cells and this has got close communication with the tympanic cavity. So therefore in a child, when a child has got otitis media or mastoiditis and mastoid abscess the infection can travel to the transverse sinus and the sigmoid sinus. What will be the manifestation? One, this person will have difficulty in hearing because of obstruction of the labyrinthine veins which are told to drain from the internal ear. Any sinus thrombosis will produce severe headache because of stretching of the dura and additionally this patient will manifest what is known as Tobi-Ire-Sine positive. What is this? Normally when we compress the internal jugular vein on any one side and we are recording spinal manometry. In a normal person it will show a transient rise in the CSF pressure because of the transient obstruction to the flow of CSF, obstruction to the flow of the blood in the jugular vein. In the case of transverse sinus thrombosis there will be no increase in the pressure CSF recording and there will be exaggerated increase in CSF pressure when the IJV on the normal side is compressed. In this connection I would like to mention that the best way to investigate these sinuses is by means of MR angiogram and the venous phase of that and which is shown in the attached radiological image on this video. So this is an MR angiogram to show the venous phase and the same picture we can also see the arteries and this is a magnetic resonance sinus venogram that will view to show only the sinus venous sinuses and this is an adioblastia view of the same to show the venous sinuses from the anterior aspect. Earlier they used to do what is known as a torcular puncture puncture through the torcular herofili and do a sinus venogram and that can also show the course of the transverse sinus and the sigmoid sinus. This is a standard sinus venogram to show the posterior sinuses the converse and the transverse of the sigmoid. When there is any pathology of the sigmoid sinus like for example thrombosis it can also second really involve the three cranial nerves which are passing through namely the 9th, 10th and 11th cranial nerves. These are some of the points pertaining to the transverse sinus and the sigmoid sinus that I wanted to mention to you. Thank you very much for watching. Dr. Sanjay Sanyal is signing out. Mr. Kendall is the camera person. If you have any questions or comments please put them in the comment section below. Have a nice day.