arteries in the neighborhood may also be involved such as the APA and OA. Other small connections are provided by arterioles of the intracavernous and supracavernous portion of the ICA that supply the sella, the Gasserian ganglion and the tentorium. The arterioles also supply the lateral wall of the CS by AMA branches and branches of the vidian artery and of the artery of the foramen rotundum.

As already discussed by Baumel and Beard (1961), there is a discrepancy between the nomenclature of this artery and the territory supplied is meningeal in only 10% (Vitek 1989). Therefore, Vitek (1989) suggested a more appropriate term, the pterygomeningeal artery. According to Lasjaunias and Berenstein (1987), the AMA can have four branches, the posterior, inferomedial, inferopalatine and intracranial branch. The latter, also named the intracranial ascending ramus, courses through the foramen ovale and anastomoses with the posteromedial ramus of the ILT. Brassier et al. (1987) emphasized the importance of these arterial anastomoses in the region of the CS and the intracavernous ICA.

3.3.2

Venous Anatomy

(Figs. 3.8–3.12 and Figs. in Sects. 7.2.13–7.2.38)

3.3.2.1

The Cavernous Sinus, Receptaculum,

Sinus Caroticus (Rektorzik), Confluens Sinuum Anterius, Sinus Spheno-Parietale (Cruveilhier), Cavernous Plexus, Lateral Sellar Compartment

nial detour through the base of the skull between two extracranial veins, the SOV and the IJV. In a typical infant stage (3rd month) the CS and the IPS have no connection with cerebral veins, the superficial middle cerebral vein (SMCV) still drains through the embryonic tentorial sinus and the superior petrosal sinus (SPS) is still not conjoined, draining only cerebellar veins. Whereas only in a typical adult stage the CS may receive blood from the SMCV, the sphenoparietal sinus (SPPS) and the SOV and drains into the inferior petrosal sinus (IPS), pterygoid plexus (PP) and SPS (Suzuki and Matsumoto 2000). The condition that the CS does not participate in the cerebral venous drainage may persist, but frequently the secondary anastomoses involving the CS occur before adult life (Padget 1956b).

This concept is not in full agreement with more recent studies on fetal skull bases by Knosp et al. (1987a) who found that in 20% the superficial middle cerebral vein drains into the CS, or the tentorial sinus has no connection to the CS. The authors further observed the SPS in 60% connected with the CS, however minor functional significance, demonstrating the prenatal existence of cerebral venous blood flow through the CS. A recent study on 270 patients using CT-angiography showed that in approximately 27% of the adult population the SMCV may not be connected to the CS (Suzuki and Matsumoto 2000).

Based on this staged embryologic development and various possibilities of persistence in adult life, the pattern of venous tributaries and drainage of the CS seen on cerebral angiograms can vary considerably.

The role of the CS as a draining pathway changes during life. As described by Padget (1956b), the CS forms during the 40-mm stage of embryonic development as a plexiform extension of the prootic sinus and the ventral myelencephalic vein. The primitive maxillary vein, initially draining into the prootic sinus, connects with the CS and becomes the superior ophthalmic vein. At the 60-mm embryonic stage, the CS is still not involved in the cerebral venous drainage and receives blood only from the ophthalmic veins draining it into the IJV via the IPS. During this time, the peri (internal) carotid venous plexus may participate instead, bringing blood from the CS through the carotid canal (Knosp et al. 1987a). Padget considered the CS and the IPS, secondary sinuses and an intracra-

The cavernous sinus (CS) belongs to the group of the great dural sinuses (sinus durae matris) which, because of their particular anatomical structure, are not named veins. An endothelial tube is surrounded by firm connective collagenous tissue without valves, but numerous lacunes and trabeculae. The CS surrounds the sphenoid bone and the pituitary gland. It forms in the middle cranial fossa a central collector for the blood coming from the meningeal veins (MV), the sphenoparietal sinus (SPPS), the superficial middle cerebral vein (SMCV) and the ophthalmic veins. The CS is located at the lateral side of the sphenoid bone, is triangular in shape and its medial border is formed by a connective tissue layer of the hypophysis. The CS has a length of approximately

20 mm and a width of 29 mm (Lang 1979a), extends from the petrous apex to the basal roots of the lesser sphenoid wing and reaches the medial part of the superior orbital fissure.

Since its very first description, controversy concerning the true anatomic structure of the CS has repeatedly occurred and persists to some extent until today.

The cavernous sinus was probably first described by Ridley (1695) as follows: “Another I discovered

by having these veins injected with wax, running round the pituitary gland on its upper side, forwardly within the duplicature of the dura mater, backwardly between the dura mater and pia mater, then somewhat loosely stretched over the subjacent gland itself and laterally in a sort of canal made up of the dura mater above and the carotid artery on each outside of the gland, which by being fastened to the dura mater above, and below at the basis of the skull, leaves only a little interstice betwixt itself

and the gland”. Winslow (1732) found the internal carotid artery “bathed in the blood of the sinus together with the third, fourth, fifth and sixth pairs of nerves”. It was Winslow who named the sinus “cavernous” because of its spongious (cavernous) structure that seemed to be formed by numerous fibers and septa of connective tissue. At the beginning of the last century, most anatomical textbooks (Huber 1930; Sobotta 1928; Spalteholz 1933), as well clinical contributions (Campbell 1933; Pace 1941) repeatedly emphasized that the lumen of the CS is crossed by numerous fibrous laminae, termed trabeculae. Knott (1882) observed that the CS “is crossed by fibrous trabeculae from some which villous process hang into the current of venous blood”.

This so-called cavernous structure has been later on increasingly questioned. Butler (1957) found that only the extended cavernous sinus in adults contains minimal filaments and those are only found close to the connections with tributaries. He did not find trabeculae in fetal sinuses.

Parkinson (1965, 1967) initially perpetuated the concept of the CS as one large venous space, but found in a later study using venous corrosion specimens that it represents an irregular plexus of varying sized venous channels, dividing and coalescing and incompletely surrounding the carotid artery (Parkinson 1973).

Also Bonnet (1957) expressed the opinion that the CS per se does not exist and the space between the dural sheets is filled by the carotid lumen, surrounded by a plexus of veins and nerves. The trabeculae seen in cadavers were probably cut walls of the small veins.

Bedford (1966) examined 34 cavernous sinuses and found in 80% an “unbroken” venous channel. She therefore proposed not to call this sinus cavernous but instead “sinus orbito-temporalis”, or as already suggested by Ridley (1695) the “circular sinus”. This concept was initially defended also by Harris and Rhoton (1976) after detailed studies on 50 cadavers. Later on, Rhoton et al. (1984) found the CS “not appearing” an unbroken cavern, but composed of several anastomosing venous channels formed by the convergence of multiple veins and dural venous sinuses. These venous channels would converge to form three main venous spaces, identified by their relationship to the ICA in medial, anteroinferior and posterosuperior compartments (Inoue et al. 1990; Rhoton et al. 1984; Oka et al. 1985). These three compartments are substantially larger than the space between the ICA and the lateral wall. The small lateral space can be so narrow that the CN VI “is adherent”

to the carotid wall medially and to the lateral sinus wall laterally (Bedford 1966).

Bedford (1966) further found that the internal carotid artery and the CN VI were outside the lumen of the sinus in 77% of the adult specimens. To consider the CS obstructive in nature and that it would predispose to thrombus formation was accordingly incorrect. Even though one may expect that thrombus formation would be seen more often in sinuses with dense trabeculae, Turner and Reynolds (1926) found only a few trabeculae in their studies on CS thrombosis.

Knosp et al. (1987a) focused in his studies on fetal cavernous sinus and preferred the term cavernous venous plexus referring to the CS as a network of distinct, individual veins.

There is otherwise no doubt that trabeculae have been found in some CS. Through the CS passes the ICA, surrounded by a plexus of sympathetic nerves. These structures are separated from the blood by a layer of endothelium. According to Lang (1979a), in an embryo there exists a venous plexus that is in 70% of the cases replaced by a single blood space, which can be traversed by 10–60 trabeculae. In 27% of the cases the CS consists of different large venous lakes that anastomose with each other. Browder and Kaplan (1976) found the outer and inner walls of the CS relatively fixed by irregularly placed strands of fibrocollagenous tissues which did not form a recognizable pattern. They further emphasized that valve-like membranes were not observed at or near the orifice of any of the tributaries.

Taptas (1987) described the cavernous sinus as a network of small caliber extradural veins and not as a single trabeculated venous canal. He gave an excellent historical overview and compared the English and French literature of the last century with German authors, revealing the numerous discrepancies in reports and anatomic textbooks between Langer (1884) and Rouviere (1985). It is astonishing, as it remains difficult to understand why for more than 100 years, particularly in the English and French literature, the concept of a large trabeculated sinus prevailed. As speculated by Taptas (1987), it may in part be due to the most convenient explanation of Nelaton’s first observation of a pulsating exophthalmos by a ruptured carotid wall and shunting blood into a large single lumen cavern. The lack of precise angiographic imaging certainly contributed to this long-lasting misconception.

The controversial terminology is continued by others (Knosp et al. 1987a; Sarma and ter Brugge

2003; Lasjaunias 1997), suggesting the term cavernous plexus because of its resemblance to other plexiform structures in the neighborhood, such as the retroclival (basilar) plexus, the venous plexus along the anterior margin of the foramen magnum (marginal sinus) and the spinal venous plexus (Brown et al. 2005).

Parkinson (2000) in a more recent communication emphasized that the term “cavernous sinus” remains one of the greatest obstacles to understanding the anatomy of the sellar and parasellar region. He suggests the term lateral sellar compartment as an enlarged segment of the extradural neural axis compartment (EDNAC). This extends from the coccyx to the orbit and contains valueless veins through which blood may run freely in either direction in addition to nervous, arterial and venous elements that may either leave or enter the compartment in its various segments.

The CS is probably neither an unbroken trabeculated venous cavern (Harris and Rhoton 1976; Inoue et al. 1990; Bedford 1966) nor a plexus of various-sized veins (Parkinson 1965, 1973; Bonnet 1957), but rather a complex venous compartment where numerous dural sinuses and veins converge to form larger venous spaces around the carotid artery which could be termed caverns (Rhoton et al. 1984).

This concept finds, at least in part, support in the angiographic pattern of the CS in normal carotid artery venograms and in the angioarchitecture of many DCSFs or CCFs. The angiographic pattern of the CS varies significantly in size and shape but is often one of a more or less single vascular space on each side of the sphenoid bone. In most direct highflow carotid cavernous fistulas (CCFs), the blood seems to shunt into a single more or less enlarged cavity in which large detachable balloons may easily migrate after being detached. Finally, in the majority of low-flow DCSF with usually multiple feeders, the shunting zone often appears rather as a single communicating venous space which can often (although not always) be approached from both sides using various CS tributaries or draining channels. A true “anatomical compartmentalization” of the CS (Chaloupka et al. 1993) may occur, but remains seldom and likely represents often a misinterpreted thrombosed CS. Platinum coils, used for transvenous occlusions, usually take a configuration that resembles rather one single venous space than a true plexus of multiple veins.

Harris and Rhoton (1976) and others (Inoue et al. 1990; Oka et al. 1985) have described three or

four main venous spaces within the CS, which they termed according to their relationship with the ICA as medial, anteroinferior, posterosuperior and lateral compartments. The medial compartment lies between the pituitary gland and the ICA, the anteroinferior compartment lies in the concavity below the first curve of the ICA, the posterosuperior compartment between the ICA and the posterior roof of the CS (Miller 1998).

The CSs communicate via intercavernous sinuses (ICSs), which have been described already by Winslow (1732) as the “inferior circular sinus” lying underneath the pituitary gland. Knott (1882) reported these connections in 6 of 44 specimens and described two intercavernous sinuses, located anteriorly and posteriorly to the hypophysis. This intrasellar venous connection through the midline has been further studied by Renn and Rhoton (1975) who concluded that an intrasellar communication between both CS may or may not be present. Typical are the anterior and posterior ICS (see below), which are named by other authors as coronary sinuses (Rabischong et al. 1974).

It is noteworthy that San Millan Ruiz et al. (1999) recently described a venous channel separate from the CS but enclosed in its lateral wall, which was found in 24% of the cases. This so-called laterocavernous sinus was found to drain the SMCVs in 22% of the cases and was separated from the CS anatomically and angiographically (Gailloud et al. 2000). Knowledge of this laterocavernous sinus may become crucial in case of a DCSF that may be not accessible. employing common transvenous approaches via the IPS or the SOV because communications between CS and laterocavernous sinus seem to be rare (3 cases in 58 specimens) (San Millan Ruiz et al. 1999).

Besides the SMCVs, the ophthalmic veins and some inferior veins of the brain are connected with the CS. The sphenoparietal sinus (SPPS) at the lower surface of the sphenoid wing, after receiving blood from several small veins of the dura mater and the anterior trunk of the middle meningeal vein (MMV), also drains into the CS. The CS communicates with the transverse sinus via the superior petrosal sinus, with the IJV via the inferior petrosal sinus (IPS), with the basilar plexus (BP), internal carotid artery venous plexus (ICAVP) and pterygoid plexus (PP) via veins through the sphenoid emissary foramen, thin veins of the canalis rotundis, larger veins of the foramen ovale, lacerum, and foramen venosum (Vesalii), and with the facial vein (FV) via the supe-