IndexTransverse and sigmoidal sinusesSuperior petrosal sinusInferior petrosal sinusTwo or three meningeal sinuses may join to form a vestibule just before reaching the superior sagittal sinus. There is a tendency for veins draining the lateral surface of the anterior frontal and posterior parietal regions to join the meningeal sinus in the dura mater lateral to the superior sagittal sinus. The veins of the posterior frontal and parietal regions most commonly dip beneath the venous lacunae and pass directly to the superior sagittal sinus. The veins of the medial surface of the hemisphere enter the inferior border of the sinus or turn laterally on the superior border of the hemisphere to join the veins of the lateral surface before entering the sinus. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original EssayThe segment of the superior sagittal sinus in the frontal region above the knee of the corpus callosum receives fewer bridging veins than any other area except the 4 to 6 cm proximal to the torcular erophilus, where bridging veins rarely enter the sagittal sinus superior. The inferior sagittal sinus (Fig 2) runs along the lower edge of the falx (16). It originates above the anterior portion of the corpus callosum and widens as it runs posteriorly to join the straight sinus. It arises from the union of the veins of the adjacent part of the falx, the corpus callosum and the cingulate gyrus. The junction of the veins of the cingulate gyrus and corpus callosum with the sinus often forms a sharp hook-shaped curve, with the apex directed forward. The major tributaries of the inferior sagittal sinus are the anterior pericallosal veins. The superior sagittal sinus can communicate through a venous canal in the falx with the inferior sagittal sinus. This connection may rarely be so large that the superior sagittal sinus drains predominantly into the inferior sagittal and rectus sinuses. Rectus sinus The rectus sinus (Fig 5) originates behind the selenium of the corpus callosum at the union of the inferior sagittal sinus and the great vein.(16)It continues posteriorly and downwards into the junction of the tentorium and falx. It may drain into one of the transverse sinuses, but more commonly it drains predominantly into the left transverse sinus. Transverse and Sigmoidal Sinuses The right and left transverse sinuses originate in the torcular herophili and run laterally from the internal occipital protuberance in a shallow groove between the attachments of the tentorium to the internal surface of the occipital bone. (16) The transverse sinus exits the tentorial attachments to become the sigmoid sinus at the site just posterior to the petrous crest, where the transverse and superior petrosal sinuses meet. Although the superior sagittal sinus may drain equally to the left and right transverse sinus or predominantly or entirely on both sides, it is the right transverse sinus that is usually larger and receives the majority of drainage from the superior sagittal sinus. The left transverse sinus is usually smaller and receives predominantly drainage from the rectus sinus. Therefore, the right transverse sinus, right sigmoid sinus, and right jugular vein contain blood from the superficial parts of the brain, while the left transverse sinus, left sigmoid sinus, and left internal jugular vein contain blood mainly from the deep parts of the brain . drained by the internal, basal, and great cerebral veins. The difference in symptoms caused by blockage of venous drainage on one side or the other and differences in Queckenstedt's sign with compression of the jugular veins on the left or right side were analyzed explained by differences in drainage on each side. Cortical veins from the lateral surface of the temporal lobe candrain into the transverse sinus, but before entering it, they commonly pass medially under the hemisphere to join a short sinus in the tentorium, which runs inside the tentorium for about 1 cm before draining into the terminal part of the transverse sinus. Cortical veins from the basal surface of the temporal and occipital lobes usually join the lateral tentorial sinus. The vein of Labbé commonly terminates in the transverse sinus, but may curve around the inferior border of the hemisphere to join the lateral tentorial sinus. The transverse sinus can communicate through the emissary veins of the occipital bone with the extracranial veins. The occipital sinus (fig 7) is the smallest of the cranial sinuses. It is located in the attached margin of the falx cerebellar, and is usually single, but occasionally there are two. It begins around the margin of the foramen magnum from several small venous channels, one of which joins the terminal part of the transverse sinus; it communicates with the posterior internal vertebral venous plexuses and ends in the confluence of the sinuses. (21) Each half of the tentorium has two constant but rarely symmetrical venous channels: the medial and lateral tentorial sinuses. (16) The medial tentorial sinuses are formed by the convergence of veins from the superior surface of the cerebellum. The medial tentorial sinuses run medially to empty into the rectus sinus or at the junction of the rectus and transverse sinuses. The lateral tentorial sinuses are formed by the convergence of the veins of the basal and lateral surfaces of the temporal and occipital lobes. The lateral tentorial sinuses arise within the lateral part of the tentorium and run laterally to drain into the terminal portion of the transverse sinus. The paired cavernous sinuses are located on each side of the sella turcica and are connected across the midline by the anterior and posterior intercavernous sinuses, which run at the junction of the diaphragm sellae with the dura lining the sella. (16) Anteriorly, each cavernous sinus communicates with the sphenoparietal sinus and ophthalmic veins. Its middle portion communicates through a lateral extension on the internal surface of the greater sphenoid wing with the pterygoid plexus via small veins passing through the foramen spinosa ovale. Posteriorly, the cavernous sinus opens directly into the basilar sinus, which is located on the clivus. It communicates through the superior petrosal sinus with the junction of the transverse and sigmoid sinuses and through the inferior petrosal sinus with the sigmoid sinus. Superior petrosal sinusThe superior petrosal sinus (fig 12) runs within the attachment of the tentorium to the petrous crest (16) Its medial end connects with the posterior end of the cavernous sinus. ü its lateral end joins the junction of the transverse and sigmoid sinuses. The bridging veins that join it usually arise from the cerebellum and brainstem, not from the cerebrum. The sinus may run above, below, or around the posterior root of the trigeminal nerve. The superficial Sylvian veins may empty into a rare tributary of the superior petrosal sinus called the sphenopetrosal sinus. Inferior petrous sinus The inferior petrous sinuses (fig 12) are small sinuses located on the lower edge of the petrous part of the temporal bone on each side (16). Each inferior petrosal sinus drains the cavernous sinus into the internal jugular vein. The inferior petrosal sinus is located in the inferior petrosal sulcus, formed by the junction of the petrous part of the temporal bone with the basilar part of the occipital bone. it begins in the postero-inferior part of the cavernous sinus and, passing through the anterior part of the jugular foramen, ends in the superior bulb of the internal jugular vein. The inferior petrosal sinus receives the internal auditory veins and also the veins of the medulla oblongata, pons, and beneath the surface of the cerebellum. The sphenoparietal sinus is the largest of the meningeal canals that run with the.