a major tributary of the external jugular vein (EJV) the pterygoid plexus may also drain via posterior and common facial veins into the IJV (Osborn 1981; Goss 1966). In some cases, the SMCV drains not via the CS but directly into the PP, a disposition identified by Osborn (1981) as the sphenobasal pattern and found in 34% of the cases. This pattern was differentiated from the sphenopetrosal pattern via the sphenopetrosal vein into the transverse sinus (13%) or a combination of both (24%).

3.3.2.4

Other Veins of Importance for the CS Drainage or for Transvenous Access to the CS

Facial Vein

The anatomy of the facial vein (FV) has been described in part above (see under SOV) and has some importance for retrograde transvenous approaches. This vein drains the anterior portion of the scalp and the soft tissue of the face and begins at the medial palpebral angle as a direct continuation of the angular vein (Osborn 1981). The FV receives the supratrochlear and supraorbital veins and descends obliquely downwards crossing the face and the masseteric muscle behind the facial artery and until it reaches the body of the mandible. Slightly inferior and anterior to the angle of the mandible, it is joined by the anterior portion of the retromandibular vein and forms the common facial vein, which usually drains into the internal jugular vein (Peuker et al. 2001). In some cases it may also drain into the EJV (Osborn 1981) and under rare circumstances even into the superficial temporal vein (Peuker et al. 2001). The FV receives blood from the ala nasi, the deep facial vein (connection to the pterygoid plexus), inferior palpebral, superior and inferior labial, buccinator, parotid and masseteric veins. Under the mandible the submental and the submandibular veins join the FV.

Frontal Vein

The frontal vein (FrV) begins on the forehead in a venous plexus which communicates with the frontal branches of the superficial temporal vein (Gray 1918). The veins converge to form a single trunk, which runs downward near the middle line of the forehead parallel with the vein of the opposite side. The two FrVs are joined at the root of the nose by a transverse branch, called the nasal arch, which receives some small veins from the dorsum of the nose. At the root of the nose the veins diverge and at the medial angle of the orbit each of them joins

the supraorbital vein to form the angular vein. Occasionally, the frontal veins join to form a single trunk, which bifurcates at the root of the nose into the two angular veins. The main stem of the FV usually forms the superior tributary to the angular vein (AV) (Doyon et al. 1974) consisting of two parts: the superior root of the SOV and the internal frontal vein. The former is accompanied by the supraorbital nerve and artery, which pass through the supraorbital notch (incisura supraorbitalis) and penetrate the orbital septum above the trochlea of the superior orbital muscle. The latter is a direct superior extension of the angular vein and has been used as a common approach to perform orbital phlebography (Doyon et al. 1974). Therefore, in case of a DCSF with prominent anterior venous drainage, it can also be used as a percutaneous approach for catheterization of the SOV and CS (Venturi et al. 2003).

Angular Vein

The angular vein (AV) represents an anastomosis between the facial vein and the SOV and is formed by the confluence of the supraorbital and frontal veins. Its subcutaneous course is down the side of the nose, lateral to the angular artery. The vein then crosses the nasal edge of the medial palpebral ligament approximately 8 mm from the internal canthus. The angular vein is continuous below with the facial vein (Doyon et al. 1974). The angular vein has three main tributaries: a medial or prenasal arch, the inferior root of the SOV and the internal frontal vein (Doyon et al. 1974).

Middle Temporal Vein

The middle temporal vein (MTV) arises near the eye, has an almost horizontal course above the zygomatic process and is connected with palpebral veins, the supraorbital vein and the facial vein. The vessel joins the superficial temporal vein to form the retromandibular vein. According to Hyrtl (1885) this vein is often found as a plexus. On angiograms it usually occurs as a single vein that has a typical acute angle when it passes over the zygomatic arch.

Because it anastomoses with the angular vein, this vessel may also be involved in the drainage of a DCSF and can be used as an approach for EVT (Cheng et al. 2003).

Internal Jugular Vein

The internal jugular vein (IJV) is the major drainage pathway for the cerebrovascular system, collecting blood from the brain, the superficial part of the face,

and from the neck (Gray 1918). The IJV begins in the posterior compartment of the jugular foramen, at the base of the skull, being continuous with the sigmoid sinus. Its origin is somewhat dilated, called the jugular bulb (JB, or superior bulb) (Gray 1918). It runs down the side of the neck, lying at first lateral to the ICA and then lateral to the CCA. Above it lies the rectus capitis lateralis, behind the ICA and the nerves passing through the jugular foramen. Lower down, the IJV and ICA lie in the same plane, the CNs IX and XII passing forward between them. The CN X descends between and behind the vein and the artery in the same sheath and the CN XI runs obliquely backward, superficial or deep to the vein. At the base of the neck the right IJV is located at a little distance from the CCA and crosses the first part of the subclavian artery while the left IJV usually overlaps the CCA. The left IJV is usually smaller and each vein contains a pair of valves approximately 2.5 cm above their termination. The most important superficial relationship of the IJV is the sternomastoid muscle, which is lateral to the vein in its upper part and covers it in its lower part. The IJV unites at the base of the neck with the subclavian vein to form the innominate vein with a little second dilatation above, called the inferior bulb.

The IJV receives blood from the sigmoid sinus, inferior petrosal sinus, facial, lingual, pharyngeal superior thyroid, middle thyroid veins and sometimes the occipital veins. In a clinical sense the most crucial relationship is with the VA and CCA/ICA because inadvertent puncture (usually of the ICA) can be a serious complication (see below).

The External Jugular Vein

The external jugular (EJV) vein drains the greater part of the blood from the exterior of the cranium and the deep parts of the face. It is formed by the junction of the posterior division of the posterior facial vein and the posterior auricular vein. This vessel originates in the substance of the parotid gland at the level of the angle of the mandible and runs perpendicularly down the neck to end in the subclavian vein (Gray 1918). It usually takes the retromandibular vein as major tributary, which is formed by the maxillary vein (draining the PP, see above) and the superficial temporal vein. There appears to be an inverse correlation between the size of the external and internal jugular vein – thus the presence of a large EJV may be an indicator of a small IJV and therefore of a potentially more difficult IJV puncture (Stickle and McFarlane 1997).

Vertebral Vein, Vertebral Artery Venous Plexus

The vertebral vein is formed in the sub-occipital angle, from numerous small tributaries of the internal vertebral venous plexuses, mainly by the confluences of the anterior and posterior condylar veins (roots) which join to form the plexus of the vertebral vein, the supply functions of which can be modified by the presence of the mastoid anastomotic emissary veins (Braum and Tournade 1977). The anterior root of the vertebral vein originates at the level of the junction of the anterior and middle thirds of the occipital venous plexus from the anterior condylar vein (venous plexus of the hypoglossal canal). It follows an oblique, outward and forward course, crossing the anterior condylar canal before it joins the posterior root of the vertebral vein. The posterior root originates at the level of the posterior third of the occipital venous plexus, crosses the atlantooccipital membrane and terminates by joining the anterior root to form the vertebral vein (Braun and Tournade 1977). The veins form a dense plexus around the vertebral artery, which descends in the canal formed by the foramina transversaria of the sixth cervical vertebrae. This vertebral artery venous plexus ends in a single trunk which emerges from the foramen transversarium of the sixth vertebra and empties into the back part of the innominate vein with a pair of valves (Gray 1918). In the sub-occipital angle the vein communicates with the anterior internal vertebral venous plexuses with the deep cervical, and occipital veins, and is joined by veins coming from the recti and oblique muscles and from the pericranium. Arnautovic et al. (1997) studied the venous anatomy of the suboccipital region in particular around the third segment (V3) of the vertebral artery and found an astonishing resemblance with the cavernous sinus, naming it accordingly suboccipital cavernous sinus.

Deep Cervical Vein

The deep cervical vein, larger than the vertebral vein, passes down the neck posterior to the cervical transverse processes. It corresponds to the deep cervical artery from which it is separated by the semispinalis cervicis muscle. It begins in the posterior vertebral venous plexus and receives tributaries from the deep muscles of the neck. It communicates or entirely drains the occipital vein by a branch that perforates the trapezius muscle. The deep cervical vein then passes forward beneath the transverse process of the seventh cervical vertebra to open into the innominate vein near the vertebral vein, or into