Confluence of Sinuses

The confluence of sinuses drains to the left and right transverse sinuses that run within the lateral edge of the tentorium cerebelli.

From: Conn's Translational Neuroscience , 2017

The Torcular Herophili (Confluence of Sinuses)

Andre Granger , R. Shane Tubbs , in Anatomy, Imaging and Surgery of the Intracranial Dural Venous Sinuses, 2020

Anatomy

The torcular Herophili (confluence of sinuses) is a highly variable structure that constitutes a vital part of the network of dural venous sinuses ( Figs. 7.1–7.5). The torcular Herophili is defined historically as the intersection of the superior sagittal sinus (SSS), the straight sinus (StS), the occipital sinus (OS) and the two transverse sinuses (TS). 1,2 Its size varies and it is located inferior to the occipital lobes and posterosuperiomedially to the cerebellum.

As a general rule, and with the torcular Herophili as the point of reference, the SSS, OS, and the StS represent inflow tracts, while the two TS represent outflow tracts. The direction of flow observed in individual specimens depends heavily on the diameters of each of the sinuses, the specific variant of the torcular Herophili present, and the presence of an intraluminal septum in the vicinity of the torcular Herophili (Fig. 7.6). Park et al. 2 observed this intraluminal septum in 16.2% (5 of 31) of specimens and Ishizaka 3 in 13% (7 of 52) of specimens.

Lamina chordae, a special type of chordae Willisii, were observed in some specimens Shao et al. 4 examined, and separated the lumen into two channels.

The central aspect of the external occipital protuberance, or the inion, was believed previously to be a reliable external anatomical landmark with which to locate the torcular Herophili. However, Tubbs et al. 5 found that this marker was unreliable, and the internal occipital protuberance, which was located inferior to the inion in the majority (73.3%) of cases was a more reliable marker. 5,6 The concavity at the internal occipital protuberance that houses the torcular Herophili is known as the torcular fossula or fossa of Zoja.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323653770000076

Surgical Nuances in Management of Intracranial Venous Sinus Injuries

Martin M. Mortazavi MD , ... R. Shane Tubbs MS, PA-C, PhD , in Anatomy, Imaging and Surgery of the Intracranial Dural Venous Sinuses, 2020

Torcular Injuries

The torcular Heterophili is also known as confluence of sinuses and is located at the occipital pole of the skull. It is formed by the merger of the SSS and the straight sinus draining most of the cerebral venous blood flow into the bilateral transverse sinuses. Although there is some parallel venous outflow through minor collateral sinuses, such as the petrosal sinuses, the torcular being the focal point of most of the cerebral venous outflow maintains dominance in the cerebral blood flow drainage. Isolated injury to the torcular is extremely rare, and only a few cases have been reported in the literature. These presented with the injury to the torcular, but only one case has been reported in which the patient suffered an isolated penetrating trauma to the torcular with a retained bullet fragment; this was successfully repaired. 8 Peritorcular meningiomas can involve the torcular, and their removal can cause iatrogenic injury to the torcular Heterophili. In studies of meningiomas involving venous sinuses, the torcular has been shown to be involved in as many as 19% of cases. 7

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323653770000271

Cerebral Vascular System

Oscar U. Scremin , in The Rat Nervous System (Fourth Edition), 2015

Superficial Venous Systems

The olfactory bulb is drained by a prominent superior olfactory sinus, and two inferior olfactory sinuses that drain into the rostral confluence of sinuses. From this point emerge the nasal emissary vein, which traverses the nasal bone and communicates with the supraorbital vein, and the olfactory emissary vein, which exits the cranium ventrally and joins the anterior communication between the two cavernous sinuses ( Figs. 14–16).

The ventral aspect of the cerebral cortex is drained, on its anterior portion, by the rostral rhinal vein, which drains into the rostral confluence of sinuses and also communicates by way of two branches with the cavernous sinus and the olfactory emissary vein. The posterior ventral aspect of the cerebral cortex is drained by the caudal rhinal vein, which empties in the transverse sinus. Both rhinal veins course on the rhinal fissure. The continuity between these two vessels is interrupted at the point where the middle cerebral artery crosses over the rhinal fissure (Figs. 15 and 16). At this level, branches of both rhinal veins flank the course of the artery for a short distance. Occasionally, a small end to end anastomosis that joins both veins is found under the middle cerebral artery. The posteromedial portion of the base of the brain is drained by the basal vein, which receives veins that run parallel to the ventral segment of the middle cerebral artery (middle cerebral vein) and to the initial segment of the anterior cerebral artery (anterior cerebral vein) (Figs. 15 and 16). It also receives veins from the anterior hypothalamic area. The basal vein drains caudally into the dorsal portion of the cavernous sinus, at the point of origin of the inferior and superior petrosal sinuses (Fig. 15). A similar vein exists in humans but, at variance with its homolog in rats, it continues dorsally to end on the great cerebral vein of Galen (Johanson, 1954; Duvernoy, 1975).The dorsal (superior sagittal and transverse sinuses and their tributaries) and ventral (cavernous sinus and its tributaries) cerebral venous systems are connected at numerous points. Intracranially, this communication is effected through a main channel, the superior petrosal sinus, which runs between the caudal termination of the cavernous sinus and the transverse sinus. The two systems also communicate by numerous anastomoses found over the surface of the cerebral hemispheres between tributaries of the basal vein and those of the anterior and posterior rhinal veins. The inferior petrosal sinus and the sigmoid sinus also connect both systems at the point of origin of the internal jugular vein and the vertebral vein and sinus (Figs. 15 and 16).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780123742452000310

The sphenobasilar synchondrosis

Torsten Liem DO Osteopath GOsC (GB) , in Cranial Osteopathy (Second Edition), 2004

Clinical presentation:

•

Region of the sigmoid sinus → pain behind the ear.

•

Region of the transverse sinus → pain in the temporal region or ipsilateral front of the head or the eye.

•

Confluence of sinuses → pain in the ipsilateral front of the head and in the eye.

•

Region of the superior petrosal sinus → pain in the temporal region.

•

Cavernous sinus → pain in the ipsilateral eye and maxillary region.

•

Region of the superior sagittal sinus and veins serving this area → pain in the frontoparietal region and region of the eye.

•

Venous stasis affecting particular segments of the brain → headache, impairment of relevant brain functions.

•

Venous stasis affecting the eyes → visual disturbances, sensation of pressure.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780443074998500089

Variations of the Intracranial Dural Venous Sinuses

Shamfa C. Joseph , ... R. Shane Tubbs , in Anatomy, Imaging and Surgery of the Intracranial Dural Venous Sinuses, 2020

Termination of the Superior Sagittal, Straight, Transverse, and Occipital Sinuses

Termination of the superior sagittal sinus into the transverse sinus is the most common anatomic variation of the sinus. It ends into the right transverse sinus in most cases (right dominance) but may also end into the left transverse sinus (left dominance) and the confluence of sinuses (codominance). This pattern of dominance varies with patient age and is more similar to the adult pattern after 5  years of age. In children less than 2   years, the codominance pattern was reported to be the highest. 97 This termination usually occurs at the level of internal occipital protuberance but may also occur above this level. In other cases, the superior sagittal sinus may fork and join with a forked straight sinus and then becomes continuous with the transverse sinus. A partition of the dura mater may also be seen in the terminal portion of the sinus, dividing this part of the sinus into unequal channels. This dural partition may also extend and divide the confluence of sinuses, the straight sinus, or the transverse sinus. In rare occasions, the superior sagittal sinus may be divided into three channels with variant terminations. In one case, this termination included a superficial threadlike transverse sinus overlying a deeper transverse sinus.

Fukusumi et al. 20 have classified the drainage pattern of the superior sagittal sinus into the transverse sinus into four types. Type I: The superior sagittal sinus reaches a centrally located confluence and then divides into the bilateral transverse sinus. Type II: The superior sagittal sinus bifurcates into right and left limbs, draining into the same side transverse sinus. Type III (most common): The superior sagittal sinus drains predominantly into the right transverse sinus. Type IV: The superior sagittal sinus drains predominantly into the left side. 20 Same classification was also applied by Singh et al. based on the occipital bone impressions for dural venous sinuses around the confluence. They also added that type I was seen more commonly in females, whereas male mostly showed type III termination. 21

Similarly, the straight sinus may reach a centrally located confluence before dividing into bilateral transverse sinus (type I), prematurely bifurcate into right and left channels before joining the corresponding transverse sinus (type II), drain predominantly into the right transverse sinus (type III), or predominantly into the left transverse sinus (type VI). 16,20 The first two types are most commonly observed, and draining into the left transverse sinus is more than the right. 23

In most cases, the occipital sinus terminates in the confluence of sinuses but may also terminate into transverse sinus, superior sagittal sinus, or straight sinus. 27 In the latter condition, the occipital sinus is termed the oblique occipital sinus and functions as the main drainage canal when the transverse sinus is rudimentary. 104,105 A more developed oblique occipital sinus was reported by Shoja et al. 107 in association with other dural variations. In this case, the sinus was found posterolateral to the foramen magnum coursing superiorly and posteromedially and connecting the terminal portion of the right sigmoid sinus to the occipital and right transverse sinuses via one medial and two lateral branches, respectively. 107 On rare occasions, the occipital sinus may drain into the superior bulb of the internal jugular vein, in association with either normal, hypoplastic, or absent transverse sinus and sigmoid sinus. 108

Based on their findings, Kopuz et al. 93 have classified the venous sinuses termination in the region of the confluence of sinuses in neonates into six types. In type I, the superior sagittal sinus was continuous with the right transverse sinus, and two occipital sinuses were opened to the confluence. In type II, the superior sagittal sinus was also continuous with the right transverse sinus, but more than two occipital sinuses were seen opening into the confluence. Types III and IV are similar to types I and II, respectively, except that the superior sagittal sinus is continuous with the left transverse sinus. In type V, the superior sagittal sinus is draining into the confluence, to which both transverse sinus and two occipital sinuses are connected. In type VI, the superior sagittal sinus bifurcates before joining the transverse sinus. 93

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323653770000258

The Peripheral and Central Nervous System

S. Franklin , in Conn's Translational Neuroscience, 2017

Dura Sinuses

The outermost layer of meninges called the dura mater can be subdivided into the outer periosteal dura mater that is fused to the overlying bone and the inner meningeal dura that is opposed to the arachnid membrane. In most regions, these layers of dura mater are fused together but in certain areas the layers of dura mater separate and create dural folds and dural venous sinuses. Dural venous sinuses are endothelial-lined spaces that receive the venous drainage from the superficial cerebral veins.

The falx cerebri is the largest dural fold that attaches rostrally to the crista galli and passes along the inner surface of the calvaria to attach to the tentorium cerebelli caudally. Along its extent the falx cerebri extends vertically from the inner surface of the calvaria to the corpus callosum separating the two cerebral hemispheres. The large superior sagittal sinus is a dural venous sinus created within the superior edge of the falx cerebri between the periosteal dura and meningeal dura. The superior sagittal sinus sweeps caudally and drains into the confluence of sinuses located at the occipital pole. The inferior sagittal sinus is formed entirely of meningeal dura at the inferior free edge of the falx cerebri. It sweeps posteriorly and first drains into the straight sinus located at the junction between the falx cerebri and the tentorium cerebelli, before draining into the confluence of sinuses.

The tentorium cerebelli forms a horizontal dural tent over the cerebellum protecting it from the cerebral hemispheres above and separating the middle cranial fossa from the inferior cranial fossa. Most of the caudal and lateral attachments of the tentorium cerebelli are to the occipital bone and parietal bone. As the tentorium sweeps forward, it attaches rostrally to the posterior clinoid processes of the sella turcica leaving a large gap called the tentorial notch on the midline. The midbrain is continuous with the diencephalon at the tentorial notch. As described previously, the straight sinus is located at the junction between the falx cerebri and the tentorium cerebelli. Located below the tentorium cerebelli is a vertically oriented dural fold called the falx cerebelli that does not truly separate the hemispheres of the cerebellum. Along the posterior edge of the falx cerebelli is the occipital sinus that drains into the confluence of sinuses. The confluence of sinuses drains to the left and right transverse sinuses that run within the lateral edge of the tentorium cerebelli. The transverse sinuses drain to the sigmoid sinuses that wind ventrally along the lateral wall to ultimately drain into the internal jugular veins.

The last dural fold is called the diaphragm sella. This dural fold is attached to all for clinoid processes of the sella turcica and creates a horizontal sheet separating the central depression of the sella turcica from the remainder of the middle cranial fossa. The pituitary stalk or infundibulum is the only structure that connects the pituitary to the hypothalamus. The diaphragm sella is also the roof of an irregular-shaped dural venous sinus in the region of the sella turcica called the cavernous sinus. The cavernous sinus drains to the transverse sinus or the sigmoid sinus by the super and inferior petrosal sinuses.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128023815000075

Diagnostic Strategies in Neonates, Children, and Young Adults with Stroke

Deborah K. Sokol , Hema Patel , in Stroke in Children and Young Adults (Second Edition), 2009

Perfusion Computed Tomography

In perfusion CT, quantitative determination of cerebral blood flow is derived via injection of intravenous iodinated contrast material followed by sequential acquisition of CT images as the dye passes through the brain. Areas of decreased perfusion appear as a change in color. 49 Serial images are obtained through the level above the confluence of sinuses at the superior sagittal sinus and at the level of the basal ganglia. Similar to conventional CT, the posterior fossa is less well defined via perfusion CT. Measures of cerebral blood flow, cerebral blood volume, and the time to peak maximal level of contrast enhancement in brain parenchyma are obtained. These values predict subsequent infarction. Prediction of acute supratentorial ischemia with 91% to 93% sensitivity has been shown for cerebral blood flow measurement, with infarction ultimately occurring in all patients with cerebral blood flow reduction of more than 70%. 50

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780750674188000045

Cerebral Venous Thrombosis

Panayiotis D. Mitsias , Jorge Burneo , in Encyclopedia of the Neurological Sciences, 2002

Anatomy of the Cerebral Venous System

The cerebral venous system consists of the cerebral veins, the posterior fossa veins, and the dural venous sinuses. All cerebral veins drain into the dural venous sinuses and ultimately into the jugular veins. There is also a collection of emissary veins, connecting extracranial veins with dural sinuses, and a basilar venous plexus around the base of the brain that communicates with the epidural venous plexus of the spinal cord.

Major portions of the cerebral hemispheres are drained by the superior sagittal sinus (SSS) and its tributaries. The deep hemispheric structures are drained by the inferior sagittal sinus, the straight sinus, and their tributaries. Both systems converge toward the confluence of sinuses (torcular Herophili). There, the SSS is often continuous with right lateral sinus, and the straight sinus is continuous with the left lateral sinus.

The dural venous sinuses (Fig. 1) consist of (i) the SSS, a midline structure between the inner table of the skull superiorly and the two leaves of the falx cerebri laterally, which runs from the crista galli to the confluence of sinuses; (ii) the inferior sagittal sinus, located in the inferior free margin of the falx cerebri, which joins the vein of Galen to form the straight sinus; (iii) the straight sinus, between the falx cerebri and tentorium cerebelli, which courses backwards to join the SSS at the confluence of sinuses; (iv) the transverse sinuses, originating at the torcular and coursing laterally; (v) the sigmoid sinuses, the continuations of the transverse sinuses, which empty into the jugular bulb at the base of the skull; and (vi) the cavernous sinuses, a collection of venous channels, which contain the internal carotid artery and cranial nerves III, IV, V1, V2, and VI and communicate superolaterally with the sigmoid sinus via the superior petrosal sinus and inferiorly with the jugular bulb via the inferior petrosal sinuses.

Figure 1. Cerebral angiography—venous phase. A, Superior sagittal sinus; B, cortical vein; C, inferior sagittal sinus; D, straight sinus; E, torcular Herophili; F, vein of Galen; G, internal cerebral vein; H, lateral sinus, transverse segment; I, lateral sinus, sigmoid segment; J, jugular vein.

The cerebral veins (Fig. 1) divide into superficial and deep veins. They do not have valves and they are much more variable than the cerebral arterial system. The superficial venous system is formed by two groups of veins—the superior group, which empties into the superior and inferior sagittal sinuses, and the inferior group, which empties into the transverse and cavernous sinuses. Important superficial veins are the superficial middle cerebral vein, the superior anastomotic vein (of Trolard), and the inferior anastomotic vein (of Labbé). The deep venous system consists of the internal cerebral veins (formed by the septal and the thalamostriate veins near the foramen of Monro), the great cerebral vein of Galen (formed by the two internal cerebral veins), and the deep middle cerebral vein, which drains the insula and forms in each side the basal vein (of Rosenthal) that empties into the great vein.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B0122268709001623

Cerebral Venous Thrombosis

J.M. Ferro , in Encyclopedia of the Neurological Sciences (Second Edition), 2014

Anatomy of the Cerebral Venous System

The cerebral venous system consists of the cerebral veins, posterior fossa veins, and dural venous sinuses. All cerebral veins drain into the dural venous sinuses and ultimately into the jugular veins. There is also a collection of emissary veins, connecting extracranial veins with dural sinuses, and a basilar venous plexus around the base of the brain that communicates with the epidural venous plexus of the spinal cord (Figure 1).

Figure 1. Schematic representation of the cerebral venous circulation. superior sagittal sinus (SLS); inferior sagittal sinus (SLI); straight sinus (SR); great cerebral vein of Galen (AG); internal cerebral vein (VG); vein of Troland (VT); vein of Labbe (VL); cavernous sinus (SC); superior petrous sinus (SPS). Reproduced with permission from University of Lisbon.

The dural venous sinuses include (1) the superior sagittal sinus (SSS), a midline structure between the inner table of the skull superiorly and the two leaves of the falx cerebri laterally, which runs from the crista galli to the confluence of sinuses (torcular herophili); (2) the inferior sagittal sinus, located in the inferior free margin of the falx cerebri, which joins the Vein of Galen to form the straight sinus; (3) the straight sinus, between the falx cerebri and tentorium cerebelli, which courses backward to join the SSS at the confluence of sinuses; (4) the transverse sinuses, originating at the torcular and coursing laterally; (5) the sigmoid sinuses, which is a continuator of the transverse sinuses, and empty into the jugular bulb at the base of the skull; the transverse and the sigmoid sinus constitute the lateral sinus; (6) the cavernous sinuses, a collection of venous channels, which contain the internal carotid artery and cranial nerves III, IV, V1, V2, and VI and communicate superolaterally with the sigmoid sinus via the superior petrosal sinus and inferiorly with the jugular bulb via the inferior petrosal sinuses. The dural sinus can have several individual anatomical variations, the most common one being the asymmetry of the lateral sinus, which is often of smaller caliber, or hypoplasic or even atretic on the left side.

The cerebral veins do not have valves, and they are much more variable than the cerebral arterial system. They are divided into superficial and deep veins. The superficial venous system is formed by two groups of veins: the superior group, which empties into the superior and inferior sagittal sinuses, and the inferior group, which empties into the transverse and cavernous sinuses. Important superficial veins are the superficial middle cerebral vein, the superior anastomotic vein (of Trolard), and the inferior anastomotic vein (of Labbé). The deep venous system drains the deep hemispheric structures and consists of the internal cerebral veins (formed by the septal and the thalamostriate veins near the foramen of Monro), the great cerebral Vein of Galen (formed by the two internal cerebral veins), and the deep middle cerebral vein, which drains the insula and forms in each side of the basal vein (of Rosenthal) that empties into the great Vein of Galen.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780123851574004115

Congenital Malformations of the Brain and Spinal Cord

Stephanie Greene , Richard G. Ellenbogen , in Pediatric Critical Care (Third Edition), 2006

Dandy-Walker Syndrome

The classic Dandy-Walker malformation is defined as aplasia of the cerebellar vermis with a posterior fossa cyst that directly communicates with the fourth ventricle. The disorder of embryogenesis is thought to be either atresia of the foramina of Magendie and Luschka or a failure of regression of the inferior medullary velum. Variants are far more common than the classic malformation and involve hypoplasia, rather than complete aplasia, of the vermis. The group of classic malformations and the variants thereof comprise the Dandy-Walker syndrome. Ninety percent of these patients have hydrocephalus (Fig. 51-5 ). The posterior fossa is usually large, with an elevated torcular (confluence of sinuses). The differential diagnosis includes mega cisterna magna (normal vermis and fourth ventricle) and posterior fossa arachnoid cyst (compressed fourth ventricle; the vermis may be difficult to identify). In the absence of hydrocephalus, these patients may be followed up clinically. If treatment is necessary, the posterior fossa cyst usually requires shunting in addition to the ventricles.

The prognosis of these patients is highly variable. Only 30% to 50% of children with Dandy-Walker syndrome have a normal intelligence quotient (IQ). The outcome does not depend on the size of the cyst, but it appears to depend more on the management of hydrocephalus and the presence of other associated anomalies. CNS anomalies include callosal agenesis, occipital encephalocele, heterotopias, and microcephaly. Associated systemic anomalies include cleft palate, microopthalmia, cardiac septal anomalies, and coarctation of the aorta. Critical to the determination of a patient's prognosis are a cranial MRI scan to search for other CNS anomalies and a thorough evaluation for systemic malformations.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323018081500547