rior ophthalmic vein (SOV). In addition, communications with the IJV via the ICAVP can be found.

The venous vessels, connected with the CS, may be divided into tributaries and draining veins, of which their functions may be changed under pathological conditions such as thrombosis, tumors or arteriovenous shunts (Miller N 1998).

The SOV, IOV, SMCV, small hypophyseal veins, and occasionally the uncal vein are considered afferent veins (tributaries). The efferent veins are the emissary veins, the IPS, and the petro-occipital sinus (if present) (Doyon et al. 1974). The SPS can drain into both the sigmoid sinus (SS) and the CS, depending on the hemodynamic balance. It is believed that the ICA pulsations support indirectly the venous flow in the CS. In case of a carotid artery occlusion this flow is slowed down and the flow in the CS may become more continuous (Doyon et al. 1974).

Table 3.3. Cavernous sinus and its main afferent (tributaries) and efferent (draining) veins CS

Afferent veins

Orbital veins

–Superior ophthalmic vein

–Inferior ophthalmic vein

–Central retinal vein (to SOV, CS)

Angular vein (to SOV)

Superficial middle cerebral vein (SMCV)

Uncal vein (UV)

Sphenoparietal sinus (SPPS)

Intracavernous sinus (ICS)

Meningeal veins

Veins of the foramen rotundum

Efferent veins

Superior petrosal sinus (SPS)

Inferior petrosal sinus (IPS)

Basilar plexus (BP)

Pterygoid plexus (PP)

Inferior petroclival vein (IPCV)

Petro-occipital sinus

Internal carotid venous plexus

Foramen ovale plexus (FOP)

Foramen lacerum plexus

(Transverse occipital sinus)

3.3.2.2

Tributaries of the Cavernous Sinus (A erent Veins)

Orbital Veins

The orbit is drained by the superior and inferior ophthalmic veins. These veins and their tributaries

are unusual in that they are without valves and are markedly tortuous with many plexiform anastomoses (Doyon et al. 1974). The complex anatomy of the orbital veins, their numerous tributaries, anastomoses and drainage pathways has been studied early on by both detailed anatomic dissections (Henry 1959),and a specifically developed radiographic technique, orbital phlebography. The latter, a major diagnostic method for intraorbital tumors and infectious diseases in the “pre CT MRI” era provided highly detailed anatomic knowledge, that still cannot be obtained today even when using high-resolu- tion MRI or DSA (Doyon et al. 1974; Fischgold et al. 1952; Hanafee et al. 1968; Lombardi and Passerini 1967, 1968, 1969; Clay and Vignaud 1974;

Clay et al. 1976; Vignaud and Clay 1974; Vignaud et al. 1972, 1974; Theron 1972; Gozet et al. 1974).

In 1755, Zinn described the superior ophthalmic vein, its course through the superior orbital fissure, and its venous anastomoses in the orbit. According to that author, Vesalius was the first to describe the ophthalmic vein as beginning at the medial angle of the eye and Fallopian was the first to describe its anastomoses with the facial vein. Walter first correctly described the anatomic relation of the superior ophthalmic vein, inferior ophthalmic vein and facial veins in 1775. In their reports, Gurwitsch (1883) and, in 1887, Festal described fairly accurately the orbital veins and their relation with the cavernous sinus, the ocular muscles, the optic nerve and the ophthalmic artery. By dissection of the veins in ten orbits that had been injected previously with gelatin, Henry (1959) described the orbital veins most accurately (Doyon et al. 1974).

Superior Ophthalmic Vein (Fig. 3.10)

The superior ophthalmic vein (SOV) is connected with all other intraorbital veins through numerous direct and indirect collaterals. The vein originates at the junction of its inferior and superior roots, also described as inferior and superior tributaries (Doyon et al. 1974). The vein measures 2 mm anteriorly and approximately 3.5 mm posteriorly, and increases in diameter at the junction of each tributary. As described by Doyon et al. (1974), the inferior root can be considered the true initial segment of the SOV belonging to the angular vein, while the superior root represents a continuation of the frontal vein. Some authors (Dutton 1994) consider the superior root the supratrochlear vein and the true SOV emerging at the junction between the infratrochlear and the supraorbital vein. As stressed by Biondi et al. (2003), this particular anatomy may

become important when performing transfacial or transophthalmic approaches. Sesemann (1869) as well as Gurwitsch (1883) divided the SOV into two or three branches that unify later on. The SOV enlarges during their course and narrows after passing the SOF, indicating that drainage is mainly posterior towards the CS. The slight enlargement before entering the CS is sometimes described as the ophthalmic sinus (Sinus ophthalmicus). Hanafee et al. (1968) and others (Doyon et al. 1974) made the suggestion to classify the SOV into three segments.

The anterior segment (first segment, Doyon et al. 1974) forms underneath the superior oblique muscle by unification of two branches, of which one comes from the supraorbital vein (often larger) and passes through the supraorbital incisura (superior root). The other originates from the angular vein (inferior root) and passes along the medial orbital wall. The anterior part of the SOV lies initially adjacent to the orbital roof, lies outside the muscle cone but is fixed by its relation to the superior oblique muscle.

The vein then enters the muscle cone about 5 mm behind the posterior pole of the globe and courses as the middle (second) segment lateral and below the superior rectus muscle and the levator palpebrae muscle dorsally to reach the superior orbital fissure (SOF). As the vein approaches the lateral wall of the orbit, it crosses the underlying optic nerve and ophthalmic artery and receives the lacrimal vein. In this segment the vein is not fixed and can be easily displaced by intraorbital masses.

The posterior (third) segment begins when the vein turns medially, posteriorly and slightly down-

wards. The SOV leaves the muscle cone, courses between the tendinous portions of the superior rectus and levator muscles and the lateral rectus muscle inferiorly. It leaves the orbit by following the lateral edge of the annulus of Zinn and then descending along the inferior edge of the superior portion of the SOF (Doyon et al. 1974). When the vein passes the fissure and enters the anterior CS its lumen is usually narrowed. On angiograms, this segment is best visible in lateral projections, starting where the vein turns downwards, and then passes through the fissure and ending at the CS (Hanafee et al. 1968;

Brismar 1974).

The SOV has connections with the veins of the face and forehead (angular vein, facial vein, frontal and temporal veins) and receives blood from the territory of the ophthalmic artery (four vortex veins of the globe, ciliary veins, central retinal veins) when passing through the orbit. The diameter of the SOV varies considerably and asymmetrical arrangement of the vein is frequently seen without underlying pathology (BrismaR 1974). The SOV receives blood mainly from two large ethmoidal veins, four vortex veins and a large lacrimal vein, which may occasionally drain into the CS separately (Miller N 1998).

Inferior Ophthalmic Vein

The inferior ophthalmic vein (IOV) is much smaller and often not visible on angiograms. It courses over the floor of the orbit, takes off branches from the inferior oblique muscle as well as from the inferior rectus muscle, drains veins of the lacrimal sac and the lower eye lid and two lower vortex veins, and

then passes with the inferior rectus muscle backwards through the orbit. It drains in the orbit into the SOV or gives off a connecting branch and empties after passing the SOF into the CS (Lombardi and Passerini 1967, 1968). According to Hanafee et al. (1986), the IOV drains directly into the PP. Browder and Kaplan (1976) found the SOV was the largest venous trunk joining the CS. According to Gurwitsch (1883) this vein may be absent in one-third of the cases and is usually an inconspicuous structure that is has been given numerous other names (Lang 1983). The existence of a third intraorbital vein, the middle ophthalmic vein, is doubtful (Lombardi and Passerini 1967).

Central Retinal Vein (No Direct CS Tributary)

The central retinal vein (CRV) drains the retina and the intraorbital parts of the optic nerve and is of special clinical significance. Formed by the union of various retinal veins at the level of the lamina cribrosa, it runs through the core of the optic nerve in company with the central retinal artery. Within the lamina cribrosa the central retinal vein anastomoses through lateral twigs with the choroidal venous plexus. In patients with occlusion or chronic compression of the CRV (Miller N 1998), these small anastomotic channels may enlarge to become optociliary veins that shunt blood from the retinal to the choroidal circulation The CRV exits from the optic nerve about 10 mm posterior to the globe, usually in company with the CRA. The vein normally courses for 4–8 mm through the vaginal spaces surrounding the nerve before it pierces the dura to exit the nerve 1–2 mm dorsal to the point of entry of the artery. The CRV may drain into the SOV, into some other orbital veins or directly into the CS (Lang 1983). It is believed that the CRV has no functionally adequate collaterals within the eyeball. Occlusion of the vein will therefore result into serious circulatory disorders with retinal venous infarcts or hemorrhages and subsequently secondary glaucoma.

Superficial Middle Cerebral Vein, Sylvian Vein

The superficial middle cerebral vein (SMCV), also called the superficial Sylvian vein (Sylvii) (Galligioni et al. 1969), originates in the posterior segment of the lateral fissure, and courses along the fissure downwards and anteriorly to reach the regio pterionalis. According to traditional views, the vein penetrates the dura and becomes a venous sinus (the sphenoidal part of the Breschet` sinus, sphenopari-

etal sinus) which courses medially along the lesser sphenoid wing to the anterior part of the CS. The existence of this connection was recently questioned by Ruiz et al. (2004) who studied the cranial venous system of 15 nonfixed human specimens. These authors could not find a connection between the SMCV and the sphenoparietal sinus in their series and, referring to the original work of Breschet, stress that this connection was in fact never illustrated in his work (see below).

Though the connection of the SMCV with the CS is not developed at birth, it forms in a later stage of life. Typically, at infant stage the vein drains posteriorly into the tentorial sinus to reach the transverse sinus. Under normal conditions and after complete development, the SMCV drains the insula, the cortex on both sides of the lateral fissure, as well as parts of the occipital and frontal lobes. It anastomoses with the deep venous system via the uncal vein, the insular vein and the basilar veins and other superficial cerebral and dural veins. It communicates also with the facial veins via the venous circulation of the orbit (Galligioni et al. 1969). It may further take off blood from the middle meningeal veins, which are connected with diploic veins and the superior sagittal sinus. The drainage system of the SMCV may show numerous variations. As a rule the SMCV as a vein of dural origin usually does not drain into the basal vein of Rosenthal, since the latter and its tributaries are derived from veins of pial origin (Huang and Wolf 1974). It may however be joined by the first or second segment of the basal vein and continue into a dural sinus.

Bisaria (1985). who studied the course of the SMCV in 140 human cadavers, found the following variations in its drainage: 51% into both SPPS, 6% into SPPS and CS, 13% in SPPS and middle meningeal veins. In 14% the vein drained into the CS alone, in 5% into the CS and meningeal veins. In one case it drained into a vein in the foramen lacerum and the SPPS, in one case into the SPPS and the SPS, in another into the middle meningeal vein on either side. The authors found one unusual drainage into the SSS and emphasize that prior to their study, the majority of the work on the termination of the SMCV was based on roentgenographic findings rather than on dissections.

Based on CT angiograms, Suzuki and Matsumoto (2000) found seven different types of drainage of which the most frequent were the sphenoparietal sinus (54%), the cavernous sinus (7%) and an emissary vein of the foramen ovale

(12%). The superficial and deep SMCVs may also drain directly into the laterocavernous sinus (San Millan et al. 1999). This work was recently complemented by Tanoue et al. 2006 who, by means of MRI examinations, simply classified the SMCV into four main types of variation. A direct connection with the SPPS and anterior CS was found in 39%, a connection with the lateral aspect of the CS independently in 30%, direct communication with the PP in 11% and a posterior course across the petrous ridge to drain into the SPS or transverse sinus in 8% of their cases.

Uncal Vein, Uncinate Vein

The uncal vein (UV) is a small, but important vein that can be angiographically identified in two out of three cases (Gozet et al. 1974). Surprisingly, this vein however, is neglected in schematic drawings of many textbooks. It passes the medial temporal lobe along the anterior margin of the uncus and drains either in the SMCV, the SPPS or directly in the CS. According to Wolf et al. (1955) this vessel marks the medial aspect of the temporal lobe and therefore has diagnostic importance. Bisaria (1985) found it in only 5% of the specimens pointing to the fact that this vein has been not described hitherto in many anatomical textbooks. The uncal vein is a derivate of the deep telencephalic vein, one of three primitive veins forming the basal vein of Rosenthal (Huang and Wolf 1974; Padget 1956a) by longitudinal anastomoses, and joins the SMCV in the neonate state, both draining into the CS. Failure of these longitudinal anastomoses is most frequent between the first and second segments of the basal vein resulting into a common stem formed by tributaries of the striate veins and posterior insular veins that drain anteroinferior into the SPPS, CS or PCS (Huang and Wolf 1974). This vein has been designated the uncal vein (Wolf et al. 1963) and may be responsible for redirection of cortical venous drainage causing intracerebral venous hemorrhage in a DCSF (Takazawa et al. 2005). Various secondary anastomoses between the SMCV, SPPS, SOV, CS and the uncal vein can occur (Huang and Wolf 1974).

Sphenoparietal sinus (Breschet), Sinus alae parvae, Sinus sphenoidales superior (Sir C. Bell)

The sphenoparietal sinus (SPPS) is the largest of the meningeal veins, usually coursing with the anterior branch of the MMA above the level of the pterion (Oka et al. 1985). The classic description of the SPPS is an antero-inferior continuation of the meningeal

sinus following the arc of the sphenoid wing and reaching the anterior CS. The term sphenoparietal sinus was introduced originally by Breschet (1829) and has been widely used in anatomical textbooks. According to him, the anterior branch of the middle meningeal vein joins a small dural sinus, the sinus of the lesser sphenoid wing (Ruiz et al. 2004). In many textbooks (Gray 1918; Lang 1979a; Osborn 1980a) and early original papers (Wolf 1963), this sinus is considered the main drainage of the SMCV to reach the cavernous sinus which is probably due to the close anatomical relationship of both vessels while coursing along the sphenoid wing. As pointed out by Padget, this sinus is not clearly defined and readily confused with a conspicuous remnant of the tentorial sinus draining the SMCV while following the lesser sphenoid wing. A true constant connection between the SMCV and the SPPS was also questioned in a recent study of Ruiz et al. (2004) who suggested instead that both veins pass next to each other but independently under the sphenoid wing to reach the cavernous sinus. This is supported by a reevaluation of original descriptions of the French anatomists Breschet (1829), Trolard (1890) and others. The authors suggest that the parietal portion of the SPPS should be rather considered a continuation of the anterior middle meningeal vein whereas the sphenoidal portion of SPPS would represent a distinct dural sinus coursing under the lesser sphenoid wing with its own tributaries. This arrangement would be more appropriately termed sinus of the lesser sphenoid wing as earlier suggested by Wolf et al. (1963).

The SPPS may join the sphenoidal emissary veins to reach the PP, or pass further posteriorly to reach the SPS or the transverse sinus (TS; lateral sinus, LS). The former variant is called sphenobasal sinus, the latter sphenopetrosal sinus. Because both are remnants of the embryonic tentorial sinus, the SMCV may also empty into these sinuses when the SPPS is absent (Oka et al. 1985). The course of the SMCV laterally over the middle cranial fossa is also named paracavernous sinus (San Millan Ruiz et al. 1999).

Intercavernous Sinus, Sinus intercavernosus, Sinus circularis (Ridley), Sinus ellipticus, Sinus coronarius, Sinus clinoideus (Sir C. Bell), Sinus transversus sellae equinae (Haller)

The two cavernous sinuses are connected by means of one or more transverse vessels, intercavernous sinuses (ICS) which cross the pituitary fossa