Veins of the Brain
The veins of the brain are thin-walled, valveless and pierce the arachnoid mater and meningeal layer of dura mater (of meninges) to empty poorly oxygenated blood into the dural venous sinuses. The dural venous sinuses drain into the sigmoid sinus which becomes continuous with the internal jugular veins (IJVs). The dural venous sinuses which receive blood from veins of the brain are:
- The superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
- Transverse sinus
- Sigmoid sinus
- Cavernous sinus
- Sphenoparietal sinus
- Petrosal sinus
- Occipital sinus.
Major veins of the brain include the superior and inferior cerebral veins, superficial middle cerebral veins, the great cerebral vein (of Galen), internal cerebral veins, as well as the superior and inferior cerebellar veins. Below is a description of veins of the brain in relation to the brain region they drain.
Veins of the cerebral hemispheres can be categorized into superficial and deep. The superficial veins chiefly drain the cerebral cortex, while the deep veins return blood from the deep structures of the cerebrum.
Superficial veins of the cerebrum
- Superior Cerebral Veins: These veins drain the upper parts of the superolateral and medial surfaces of the cerebral hemisphere. They drain blood into the inferior and superior sagittal sinuses.
- Inferior Cerebral Veins: These veins return blood from the inferior aspect of the cerebral hemisphere into the transverse, superior petrosal, cavernous and sphenoparietal sinuses. Some also drain into the inferior sagittal sinus.
- Superior Middle Cerebral Vein: This vein receives blood from veins on the superolateral surface, as it lies superficiallyalong the lateral sulcus and the posterior ramus of lateral sulcus. The posterior end of this vein is connected to thesuperior sagittal sinus by the superior anastomotic vein (this is so because of its curve along the posterior ramus of lateral sulcus). The superior middle cerebral vein is also connected to the transverse sinus by the inferior anastomotic vein. It terminates in the cavernous sinus.
Deep veins of the cerebrum
Internal structures of the cerebrum are drained by the following deep veins and their tributaries:
- Two internal cerebral veins
- The great cerebral vein (of Galen)
- Two basal veins.
All of those deep veins and their tributaries drain the thalamus, hypothalamus, the corpus striatum, internal capsule, corpus callosum, septum pellucidum, the choroid plexuses and the white matter of the cerebral hemispheres.
- Internal Cerebral Veins: Each internal cerebral vein begins at the interventricular foramen (of Monro), and runs backwards in the tela choroidea, in the roof of the third ventricle. The two internal cerebral veins merge to form the great cerebral vein, and one of its major tributaries is the thalamostriate vein, which lies in the floor of the lateral ventricle and returns blood from the caudate nucleus (a basal ganglia nucleus) and the thalamus. In addition, the corpus striatum (input unit of the basal ganglia) and internal capsule are drained by the superior and inferior striate veins. These veins drain into the internal cerebral vein and the basal vein respectively.
- Basal Veins: The two basal veins wind around the midbrain to drain blood into the great cerebral vein. Each of these veins is formed by the union of the anterior cerebral vein (a vena comitants), deep middle cerebral vein, and some inferior striate veins, and begins near the anterior perforated substance.
- The Great Cerebral Vein: This vein which is formed by union of the two internal cerebral veins passes posteriorly beneath the splenium of the corpus callosum, to end in the straight sinus. It receives blood from the basal veins, some veins from the occipital lobes, and some from the corpus callosum.
The cerebellum is drained by the superior and inferior cerebellar veins and their tributaries. From the upper surface of the cerebellum, blood is drained into the straight, transverse, and superior petrosal venous sinuses. The inferior cerebellar veins and their tributaries drain blood into the right and left sigmoid sinuses, inferior petrosal sinus, the occipital and straight sinuses.
Veins of the brainstem are tributaries of the great cerebral vein and basal vein. They are continuous with veins of the spinal cord, inferiorly. Those tributaries on the midbrain drain into the great cerebral vein or into the basal vein. Those within the pons and medulla, drain into the superior and inferior petrosal sinuses, the transverse sinus and into the occipital sinus.
Subdural Haemorrhage: The subdural haemorrhage is a type of intracranial haemorrhage which is usually caused by rupture of cerebral veins as they course through the space between the dura mater and arachnoid mater to reach the venous sinuses. This can occur in the event of an accident head to head injuries. Such bleeding (haemorrhage) can be extensive and can act as a space occupying lesion.