Video: Superficial veins of the brain
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Hey everyone! It’s Nicole from Kenhub, and welcome to this tutorial on the superficial veins of the brain. In this tutorial, we’re going to be looking mainly at this image of the cerebrum which is ... Read more
Hey everyone! It’s Nicole from Kenhub, and welcome to this tutorial on the superficial veins of the brain. In this tutorial, we’re going to be looking mainly at this image of the cerebrum which is a lateral view of the left cerebral hemisphere with its anterior aspect over here, our posterior aspect over here, our cerebellum down here, and our brainstem just inferior to that. As you can see, the superficial surface of the cerebrum has many venous structures, otherwise known as the superficial veins of the brain which of course is the topic of our tutorial today.
Before we go on to talk about the superficial veins of the brain, I first want to introduce you to the concept of the cerebral veins in general – that is, the veins that drain the parenchyma of the brain. It’s important to note that unlike the veins of the rest of the body, the veins of the brain are thin-walled and valveless. There are 2 types of venous systems found within the cerebral vein. These are the superficial venous system which primarily drain the grey matter of the brain and the deep venous system which drain the deep structures of the brain and the white matter of the cerebral hemispheres. Both sets of veins drain into the internal jugular vein. However, since our focus of today is on the superficial veins of the brain, we’ll leave a deeper discussion of the deep veins through another tutorial.
Let’s have a chat now about the function and location of the superficial veins of the brain. As we mentioned, the main role of the superficial veins of the brain is to drain blood from the grey matter and superficial-most white matter of the cerebral cortex. As you can probably guess from their name, the superficial veins of the brain are the veins found on the surface of the cerebrum. More specifically, they’re found in the subarachnoid space – that is, between the arachnoid mater and the pia mater. In this cranial view of the brain, you can see the superior cerebral brains running between the pia mater which itself is running over the surface of the cerebrum and the arachnoid mater which is the layer lying superficial to the pia mater.
Let’s take a couple of minutes to talk about the drainage of the superficial veins of the brain. As you can see on the image, the superficial veins of the brain form an anastomotic network connecting extensively with each other and the deep cerebral veins. The superficial veins of the brain drain blood from various regions into sinuses in the brain. The frontal and parietal lobes drain into the superior sagittal sinus and blood from the temporal and occipital lobes drain into the right and left transverse sinuses, though in this image, we’re only looking at the left transverse sinus. The deep cerebral veins drain either into the straight sinus or the transverse sinuses but again we’ll talk more about these in another tutorial.
Before we move on to talk about the superior cerebral veins in a bit more detail, I just wanted to talk through the pathway of the superficial veins of the brain using this cranial view of the cerebrum and the superior cerebral veins of the brain. In contrast to most of the body, the superficial veins of the brain do not follow the arteries. Instead from the structures they drain, their path takes them across the brain surface in the subarachnoid space where they pierce the arachnoid mater, cross the subdural space and then pierce the meningeal layer of the dura mater to finally drain into the dural venous sinuses. In this case, we’re looking specifically at an image of the superior cerebral veins draining into the superior sagittal sinus which you can see highlighted in green on the image on the right. Blood then empties into the sigmoid sinus which is continuous with the internal jugular veins inferiorly.
As we mentioned, there are quite a few superficial veins of the brain and as their size and parts vary from person to person, the clearest way to discuss the superficial veins of the brain is to group them based on what parts of the cortex they drain. The veins we’ll be looking at today therefore include the superior cerebral veins and the superficial middle cerebral vein of Sylvius, the 2 anastomotic veins – one superior and one inferior – and the inferior cerebral veins. Let’s begin, of course, with the superior cerebral veins.
The superior cerebral veins are a network of interconnected veins found within the subarachnoid space. As you can see, the superior cerebral veins travel over as well as drain the anterior, superior, lateral and medial areas of the cerebral cortex. These areas include the anterior, superolateral and medial surfaces of the frontal lobes; the anterior, superolateral and medial surfaces of the parietal lobes; and the superolateral, medial and posterior surfaces of the occipital lobes. As you can see, the superior cerebral veins drain into the superior sagittal sinus.
The superficial middle cerebral vein of Sylvius, sometimes referred to as the Sylvian vein, is a single vein present laterally on both sides of the brain. It’s found in the subarachnoid space. In terms of its pathway, it descends anteriorly along the lateral sulcus also known as the Sylvian fissure then curves medially along the sphenoid ridge which is not yet visible in this image. In terms of its areas of drainage, the superficial middle cerebral vein drains the lateral surfaces of the frontal, parietal and temporal lobes. Finally, the vein continues from the sphenoid ridge to drain into the cavernous sinus which you can see in our image of the skull with a sagittal and transverse section cut away.
The next vein I’d like to discuss is the superior anastomotic vein of Trolard – another single vein present on both sides of the cortex. As the above two veins, it is found in the subarachnoid space. In terms of its pathway, it connects the superficial middle cerebral vein to the superior sagittal sinus by arcing over the superior lateral surface of the parietal lobe. As you can guess from its course, it is responsible for the drainage of the superolateral parietal cortex and drains into the superficial middle cerebral vein and the superior sagittal sinus.
The third single vein of the superficial cerebral veins is the inferior anastomotic vein of Labbé. Like the others, it is present bilaterally and it is situated in the subarachnoid space. An important thing about this vein to note is that this vein is not present in everyone. In addition, its exact position varies. In terms of its pathway, the inferior anastomotic vein connects the superficial middle cerebral vein with the transverse sinus. In most people, the vein runs over the mid-temporal region which on this image is around about there. And of course in terms of its drainage, the inferior anastomotic vein drains the lateral aspects of the temporal lobes and subsequently drain into the superficial middle cerebral vein and the transverse sinus.
The last group to discuss are the inferior cerebral veins – a network within the subarachnoid space. Note that this lateral view shows only one of the many possible exit points of these veins. Since the inferior cerebral veins have a close relationship with the deep venous structures, the inferior cerebral veins are known to have a slightly more complex route. Although it’s a bit difficult to see on this image, the inferior cerebral veins course over and drain the inferolateral surfaces of the temporal lobes and the orbital surfaces of the frontal lobes. Unlike the rest of the superficial cerebral veins which drain into the venous sinuses, blood drained through the inferior cerebral veins travels to the closest deep venous sinuses or the deep veins. Let's first have a look at which deep venous sinuses the inferior cerebral veins drain into.
There are five sinuses that receive drainage from the inferior cerebral veins. In this image of the skull with the section cut away along the sagittal and transverse planes, you can see the transverse sinuses and the superior petrosal sinuses, the cavernous sinus, the sphenoparietal sinuses and the inferior sagittal sinus. Let's now take a look at the deep veins the inferior cerebral veins can drain into. The only deep vein the inferior cerebral veins drain into is the basal vein which you can see on this view of the medial aspect of the right cerebral hemisphere highlighted in green. It is important to note that there is a basal vein associated with each cerebral hemisphere – a left and right basal vein. Nevertheless, the basal veins travel posteriorly and around the midbrain. The inferior cerebral veins on the inferolateral surfaces of the temporal lobes on the other hand drain to the closes deep venous structure.
Before we finish this tutorial, let's have a brief chat about some clinical conditions associated with the superficial veins of the brain. Knowing about the veins of the brain is clinically important in the situation of subdural haemorrhage. A subdural haemorrhage is a venous bleed in the brain which arises due to the tearing of superficial cerebral veins as they pass through the subdural space. Remember at the top of this tutorial, I mentioned how the veins pierce the arachnoid mater across the subdural space and pierce the meningeal layer of the dura mater to empty into the deep venous sinuses. These two layers – the dura mater and the arachnoid mater have the ability to slide over each other. When the head is jolted usually by trauma, the arachnoid mater moves quickly in relation to the dura mater putting stress on the bridging veins and causing some to break. Normally, this would result in clotting but if the sufferer has clotting problems for example, the patient who is on a blood thinning medications such as warfarin or a patient who has a coagulopathy, the bleeding will slowly continue. The consequence of this is a haematoma which acts as a space-occupying lesion with the skull. This condition is life-threatening and it's critical that a quick and through history and examination be conducted for the condition to be treated quickly.
So thank you for watching this tutorial and in summary let's briefly go over what we've discussed today. The superficial cerebral veins are a network of veins draining the grey matter and superficial-most white mater. The superficial cerebral veins occupy the subarachnoid space crossing the subdural space to drain to the local dural venous sinuses. A knowledge of their anatomy is clinically important in cases of subdural haemorrhage which is caused by the tearing of these veins as they traverse across the subdural space.
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