Venous drainage of head and neck/ dental implant courses by Indian dental academy

GITAM DENTAL COLLEGE & HOSPITAL

DEPARTMENT OF ORAL & MAXILLOFACIAL SURGERY

SEMINAR ON Venous drainage of head & neck region & spread of infection through venous drainage

Presented By:

Dr. Sambhav K Vora

I MDS

Contents 1. Introduction 2. Classification of veins 3. Veins of head & neck 4. Veins of scalp & face 5. Variations in the superficial cervical veins 6. Sinuses of the duramater 7. Emissary veins 8. Diploic veins 9. Spread of infection through the venous drainage 10.Cavernous sinus thrombosis.

Aim: To study the course & position of the veins of the head & neck & its protection while performing surgeries related to that area.

The venous blood of head &neck is drained almost entirely by the internal jugular vein, which joins the subclavian vein, behind the sternoclavicular articulation to form the brachiocephalic vein. The two brachiocephalic vein unites to form the superior vena cava. Along the neck .two superficial veins are added to the deep internal jugular vein namely the external & anterior jugular vein.

CLASSIFICATION OF VEINS;  Veins of exterior of head &neck  Cervical veins  Diploic, meningeal, &dural venous sinuses

VEINS OF THE NECK Veins of the neck are superficial and deep to the deep fascia. Superficial veins are anterior jugular, external jugular and posterior jugular veins; they drain a smaller part of tissue than deep veins. Deep veins drain all subcutaneous structures mostly internal jugular veins and into the subclavian

vein.

Superficial veins

Deep veins

VEINS OF HEAD &NECK Vein Termination Superficial veins Common facial 1.facial vein

Tributaries 1.supratrochlear 2.supraorbital 3.nasal 4.superior labial 5.inferior labial 6.muscular 7.submental 8.tonsillar

2.superficial

9.

Submandibular.

Retromandibula 1.scalp

Areas drained Scalp, forehead .upper eyelid Scalp,forehead,uppe r eyelid External nose Upper lip Lower lip Masseter & buccinator muscle Sub mental structure Palatine tonsil&tonsillar bed Submandibular gland Anterior & posterior

temporal

r 2.glandular 3.auricular 4.articular

3.pterygoid plexus of veins

Maxillary veins &small contribution to cavernous sinus

5.transverse facial 1.infraorbital

2.sphenopalatine 3.muscular 4.buccal 5.palatine a. greater palatine b. lesser palatine 6.inferior alveolar a. mental 7. deep facial 4.maxillary Retromandibula Pterygoid plexus r Retromandibula Anterior & 1.superficial r posterior temporal divisions 2.maxillary Common facial Internal jugular 1.facial 2,retromandibula r (anterior division) External jugular Subclavian 1.retromandibula r (posterior

region of scalp Parotid gland External ear Temporomandibular joint Side of the face &cheek.

Lower eyelid, external nose, upper lip , maxillary teeth Nasal cavity, anterior end of hard palate Muscles of mastication Cheek & buccal mandibular gingivae Posterior two thirds of the hard palate Soft palate Mandibular teeth Lower lip, chin, mandibular labial gingivae A direct communication with the facial See above See above See above

See above

division) 2.posterior auricular 3.transverse cervical 4.suprascapular 5.anterior jugular

Scalp posterior to ear, external ear Neck Neck &upper back Structures of the anterior triangle of the neck.

INTERNAL JUGULAR VEIN: The internal jugular vein receives blood from the brain, face, &neck. It commences at the jugular foramen in the skull as the continuation of the sigmoid sinus it descends through the neck in the carotid sheath &unites with the subclavian vein behind the medial end of the clavicle to form the brachiocephalic vein, immediately below the jugular foramen the vein is widened to form the superior bulb of the internal jugular vein which is contained in the jugular fossa on the inferior surface of the temporal bone.

Relations: Anterolaterally –skin, fascia, sternocleidomastoid, &the parotid salivary gland

Lower end is covered by the sternothyroid, sternohyoid, & omohyoid muscles Higher up is crossed by stylohyoid, posterior belly of the digastric &the spinal accessory nerve Posteriorly-transverse process of cervical vertebrae, levator scapulae,scalenus medius,scalenus anterior ,cervical plexus,phrenic nerve,thyrocervical trunk, vertebral vein,& the first part of subclavian artery Medially –above lies the internal carotid artery& the ninth, eleventh, &twelfth cranial nerves. Below lies the common carotid artery & the vagus

nerve.

TributariesInto the superior bulb opens the inferior petrosal sinus, Veins of the pharynx tongue. &sublingual area drain upper part of the internal jugular vein, Anastomosis between internal &external jugular vein is seen near the upper corner of the carotid triangle.,

Facial vein along with anterior division of the Retromandibular vein joins the internal jugular vein.

Veins of the larynx & thyroid glands are main tributaries at the lower part of the neck, Lingual veins-it drains the tongue & sublingual region. It has 3 division’s namely dorsal veins, deep veins & sublingual vein. The largest of these veins is the sublingual vein, which accompanies the hypoglossal nerve .vein of the tongue may join single large trunk or may empty separately into the internal jugular vein Surface marking: it is along a line from the lobule of the ear to the sternal end of the clavicle, between the two heads of the sternocleidomastoid, .In the neck the internal jugular vein lies lateral to the common carotid artery, in front of the scalenus anterior. .The jugular venous pulse is a guide to the jugular venous pressure. With the patients reclining at 45 degrees the jugular venous pulse should be visible just above the clavicle.

Ansa cervicalis lies in the front of the internal jugular vein & gives branches to the infra hyoid muscles.

Catheterization: the right internal jugular vein can be cannulated for the insertion of the central venous line, for measurements of central venous pressure, or the rapid administration of the drugs when the peripheral approach would be too slow. The vein is usually approached through the centre of the triangle formed by the two heads of the sternocleidomastoid &clavicle. The needle is directed caudally ,parallel to the sagittal plane at a 30 degree posterior angle with the coronal plane, entering the vein in about 4 -5 cm.

Complications-hematoma formation, common carotid artery puncture, vagus nerve injury, & pneumothorax due to pleural perforation.

Pulsations of the IJV caused by contraction of the right ventricle of the heart may be palpable superior to the medial end of the clavicle. The pulsations usually are visible when the person’s head is 10 to 25° lower than the feet.

Because there are no valves in the brachiocephalic vein or superior vena cava, a wave of contraction passes up these vessels to the IJV. The presence of valves in the IJV and subclavian vein, near their respective junctions prevents backflow during heart contractions

INTERNAL JUGULAR VEIN PUNCTURE A needle and catheter may be inserted into the IJV for diagnostic or therapeutic purposes. During this procedure, the clinician palpates the common carotid artery and inserts the needle into the IJV just lateral to it at a 30° angle, aiming at the apex of the triangle between the sternal and clavicular heads of the SCM. The needle is then directed inferolaterally toward the ipsilateral nipple.

EXTERNAL JUGULAR VEIN It drains mainly scalp and face. .it is formed by the union of posterior division of the retromandibular vein with the posterior auricular vein and begins near the angle of the mandible just below or in the parotid gland.

From here it descends obliquely superficial to the sternocleidomastoid to the root of the neck and then it crosses the deep fascia and ends in the subclavian vein. Although valves are present in the external jugular vein but it doesn’t prevent regurgitation. It is covered by the platysma, superficial

fascia and the skin.

Tributaries – it receives the posterior external jugular vein and transverse, cervical , suprascapular and anterior jugular vein near it s end. It is also joined by the branch from the internal jugular vein near the parotid gland.

PROMINENCE OF EXTERNAL JUGULAR VEIN

When venous pressure is within the normal range, the blood distending the EJV is either not apparent or observable for only a short distance at the base of the neck. However, when the pressure rises – as during heart failure for example – the EJV becomes prominent throughout its course along the side of the neck. Consequently, routine observation for distention of the EJV during physical examinations may reveal diagnostic signs of heart failure, obstruction of the superior vena cava (e.g. by tumour cells), enlarged supraclavicular lymph nodes, or increased intrathoracic pressure SUBCLAVIAN VEIN PUNCTURE The right subclavian vein often is the point of entry to the venous system for central line placement. This technique is used to administer parenteral fluids (nutritional fluid not introduced via the digestive system) and medications and to measure the central venous pressure. The pleura and/or the subclavian artery are in danger of puncture during this procedure.

POSTERIOR EXTERNAL JUGULAR VEIN It begins in the occipital scalp and drains into the skin and the superficial muscles in the postero superior region of the neck. It joins the middle part of the external jugular vein.

ANTERIOR JUGULAR VEIN It arises near the hyoid bone and descends between the midline and the anterior border of the sternocleidomastoid. Deep to the sternocleidomastoid it joins the external jugular vein or may enter subclavian vein directly. There are usually two anterior jugular veins which are united just above the manubrium by large transverse jugular arch which receives the inferior thyroid tributaries.

FACIAL VEIN:-it is the main vein of the face. It travels obliquely downwards by the side of the nose &descends to the anterior border & then passes over the surface of the masseter. It crosses body of the mandible &runs in the neck to drain into the internal jugular vein. The common facial vein originates below the angle of the mandible from the junction of the facial &retromandibular vein, above its junction with the superior labial vein it is termed as angular vein. The angular vein receives the frontal vein, supraorbital vein, veins from the lower lid &from the bridge of the nose.

Supraorbital vein begins

near the zygomatic process of the frontal bone, passes medially piercing the orbicularis oculi&unites with the supratrochlear vein .frontal &supra orbital veins anastomoses through wide venous nets with the other veins of the scalp. Superficial temporal, posterior auricular &occipital veins. The angular vein is constantly in communication with the superior ophthalmic vein jus above the medial palpebral ligament,& as superior ophthalmic vein opens into the cavernous sinus a link between facial vein & intracranial sinuses of the duramater is seen Facial vein lacks valves & because of its connection with the cavernous sinus it has the clinical significance in the spread of infection.

superficial temporal vein: it begins from the wide spread plexus of veins on side of the scalp &along zygomatic arch.frontal & parietal tributaries unite anterior to the auricle, crosses temporal root of zygomatic arch to pass from the temporal region & enter the substance of the parotid gland.it joins maxillary vein posterior to the neck of the mandible to form the retromandibular vein.

Retromandibular vein: It is formed by the union of the superficial temporal & maxillary vein in the substance of the parotid gland behind the neck of the mandible.the vein emerges at the lower pole of the gland to unite with the facial vein,it continues downwards on the outer surface of the stylohyoid &digastric muscles In some cases however the a deep branch of retromandibular vein follows the external carotid artery in its deep course &empties into the internal jugular vein.

Above the root of zygomatic arch ,a middle temporal vein opens into the superficial temporal vein. This middle temporal vein drains into the venous plexus situated underneath the temporal fascia The two maxillary veins are the outlet of the large &dense pterygoid venous plexus which surrouds the maxillary artery in the infra temporal fossa.

Pterygoid plexus of veins: Veins of the deep structures of the face open here. It is situated between the temporal &lateral pterygoid or between the lateral &medial pterygoid muscles depending on the course of the maxillary artery..anteriorly it reaches the tuberosity of the maxilla ,superiorly to the base of the skull.

Tributaries-veins of the masticatory muscles,sphenopalatine veins ,draining posterior part of the nasal cavity &greater part of the palate , middle meningeal veins draining the duramater , articular veins from rich plexus in &around the capsule of the mandibular joint,auricular veins from the external ear, transverse facial vein draining the posterior part of the cheek & the parotid gland.

The dense venous plexus surrounding the maxillary artery serves to protect the artery from the compressionwhen the masticatory muscles contract.

During their contraction the bulging muscles drive blood from the veins &during relaxation the veins fill again.this type of mechanical protective functions of veins is very rare & is seen in the venous plexus surrounding the internal carotid artery in the carotid canal.

Variations in the superficial cervical veins The most important and frequent variations are:1. the common facial vein does not exist. The retromandibualr vein continues into the external jugular vein, the facial vein opens into the internal jugular r vein.

2. the retromandibular vein opens into the internal jugular vein, the facial vein continues intot the anterior jugular vein, and a common facial vein again is absent.

3. the common facial vein loses its connection with the internal jugular vein and empties instead into the external jugular vein.(choudhary et al ) 4. retromandibular vein continues into the external jugular vein, facial vein continues into the anterior jugular vein.

5. In one of the cadavers the following variation was observed, the facial vein was found running downward & backwards at the anterior border of masseter,where the submental vein united with the facial vein to form a common venous channel.the common venous channel united with the retromandibular vein at the angle of the mandible to form the common facial vein. Before this common facial vein joins the internal jugular vein , a venous channel originating from the anterior jugular vein comes & joins the common facial vein &which then joins the internal jugular vein.( j anat.soc.india,52(1),64-65 (2003)) 6. A case of facial vein uniting with the superficial temporal vein 5 mm cranial to the undivided part of retromandibular vein has been reported by Peuker et al (2001)

VEINS OF THE SCALP & FACE: The superficial part of scalp is drained by supra orbital &supra trochlear veins.

Supratrochlear vein- it starts from the venous network connected to the frontal tributaries of the superficial temporal vein, it descends near the midline to the bridge of the nose.where it unites with the supraorbital vein to form the facial vein near the medial canthus of the eye.

Supraorbital vein begins near the zygomatic process of the frontal bone,passes medially piercing the orbicularis oculi&unites with the supratrochlear vein .frontal &supra orbital veins anastomose through wide venous nets with the other veins of the scalp.superficial temporal,posterior auricular &occipital veins.

SINUSES OF THE DURAMATER The blood of the brain and the eye is collected by system of specialized vein in the duramater called sinuses. These sinuses are non collapsible and are formed by the dense rigid and inelastic tissue of the duramater. They drain eventually into the internal jugular vein but there are numerous communications between the sinuses and the extracranial vein.

SUPERIOR SAGITTAL SINUS This sinus commences in the region of crista gali of the ethmoid bone and curves posteriorly in the midline over the frontal, parietal and occipital bones. On its way it receives numerous veins from the convexity of the brain.

Arachnoid granulations are small cauliflower like extension that protrude into the lateral aspects of the superior saggital sinus .csf leaks back across the arachnoid membrane through these archnoid granulations to enter the venous blood of the superior sagittal sinus.

INFERIOR SAGITTAL SINUS A narrow sinus, enclosed in the lower free border of a sickle shape median fold of the dura, the falx cerebri which separates the two hemispheres of the cerebrum.

STRAIGHT SINUS A roughly horizontal fold of the dura between the cerebrum and cerebellum,meets the inferior saggital sinus joins with a deep vein of brain

&continues backwards &downwards as the straight sinus.it unites with the superior saggital sinus at the inner occipital eminence.

OCCIPITAL SINUS: This small vein begins on either side of the great occipital foramen &ascends in the midline.it ends at the inner occipital eminence.

TRANSVERSE SINUS; The point where the superior saggital sinus ,straight sinus ,&occipital sinus unite is called the confluence of the sinuses.from here the blood is drained by the paired transverse sinus.,sometimes the straight &superior saggital sinus do not join but continue each into one transverse sinus,even if they join also a greater amount of blood usually enters into the right transverse sinus than the left, as a consequence the right internal jugular vein is often much larger than the left.

The transverse sinus runs almost horizontally across the occipital bone &then over the temporal bone to the point where the superior crest of the temporal pyramid commences.from this point the transverse sinus continues in an s shaped curve as the sigmoid sinus,descending towards the cranial base ,the sigmoid sinus continues through the jugular foramen into the internal jugular vein.

CAVERNOUS SINUS: it is a large venous space situated in the middle cranial fossa on either side of the sphenoid bone. The floor of the sinus is formed by the endosteal duramater .the lateral wall, roof, &medial wall is formed by meningeal duramater. Anteriorly the sinus extends up to the medial end of the superior orbital fissure &posteriorly up to the apex of

petrous temporal bone.

Relations – Structure outside the sinus-

a.superiorly : optic tract,optic chiasma,olfactory tract,internal carotid artery, b.inferiorly:foramen lacerum & the junction of the body &greater wing of sphenoid bone c.medially:hypophysis cerebri &sphenoidal air sinus d.laterally:temporal lobe with uncus e.anteriorly:superior orbital fissure & the apex of the orbit f.posteriorly:apex of the petrous temporal & the crus cerebri of the mid

brain structure in the lateral wall of the sinusa.occulomotor nerve- in the anterior part of the sinus,it divides into the superior &inferior divisions which leave the sinus by passing through the superior orbital fissure b. trochlear nerve-it enters the orbit through superior orbital fissure c.opthalmic nerve-in the anterior part of the sinus it divides into the lacrimal,frontal,& nasociliary nerves d.maxillary nerve-it leaves the sinus by passing through the foramen rotandum e.trigeminal ganglion structures passing through the centre of the sinus: a. internal carotid artery with the venous & sympathetic plexus around it.

b. Abducent nerve-inferolateral to the internal carotid artery.

Tributaries or incoming channels: From the orbita.superior ophthalmic vein b. branch of inferior ophthalmic veinor sometimes the vein itself. c.the central vein of retina may drain into the superior ophthalmic vein or into the cavernous sinus.

From the braina.superficial middle cerebral vein b. inferior cerebral veins from the meningesa. Sphenoparietal sinus b. Frontal trunk of middle meningeal vein which may drain into the pterygoid plexus through the foramen ovale or into the sphenoparietal or cavernous sinus.

Draining channelsor communicationsa. Transverse sinus through the superior petrosal sinus b. Internal jugular vein through the inferior petrosal sinus &through a plexus around the internal carotid artery. c. Pterygoid plexus of veins through the emissary veins passing through the foramen ovale,foramen lacerum& the emissary sphenoidal foramen d. Facial vein through the superior ophthalmic vein e. Right &left cavernous sinuses communicate with each other through the anterior &posterior intercavernous sinuses &through the basilar plexus of veins. superior petrosal sinus (sinus petrosus superior) small and narrow, connects the cavernous with the transverse sinus. It runs lateralward and backward, from the posterior end of the cavernous sinus, over the trigeminal nerve, and lies in the attached margin of the tentorium cerebelli and in the superior petrosal sulcus of the temporal bone; it joins the transverse sinus where the latter curves downward on the inner surface of the mastoid part of the temporal. It receives some cerebellar and inferior cerebral veins, and veins from the tympanic cavity.

Inferior petrosal sinus (sinus petrosus inferior) is situated in the inferior petrosal sulcus formed by the junction of the petrous part of the temporal with the basilar part of the occipital. 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 veins from the medulla oblongata, Pons, and under surface of the cerebellum.

Relations: of the parts to one another in the jugular foramen is as follows: the inferior petrosal sinus lies medially and anteriorly with the meningeal branch of the ascending pharyngeal artery, and is directed obliquely downward and backward; the transverse sinus is situated at the lateral and back part of the foramen with a meningeal branch of the occipital artery, and between the two sinuses are the glossopharyngeal, vagus, and accessory nerves. These three sets of structures are divided from each other by two processes of fibrous tissue. The junction of the inferior petrosal sinus with the internal jugular vein takes place on the lateral aspect of the nerves.

SIGMOID SINUS: it continues medially from the transverse sinus & ends at the mouth of the jugular foramen. Thus all venous blood ultimately collected by the sigmoid sinus drains through the jugular foramina to the internal jugular vein below.

BASILAR SINUS: it lies below the Dura of the clivus, scattered in a plexiform fashion. It receives blood from the cavernous sinus inferior petrosal sinus &then drains to the vertebral plexus of veins through the foramen magnum.

Emissary Veins (emissaria).—the emissary veins pass through apertures in the cranial wall and establish communication between the sinuses inside the skull and the veins external to it. Some are always present, others only occasionally so. The principal emissary veins are the following: (1) A mastoid emissary vein, usually present, runs through the mastoid foramen and unites the transverse sinus with the posterior auricular or with the occipital vein.

(2) A parietal emissary vein passes through the parietal foramen and connects the superior sagittal sinus with the veins of the scalp.

(3) A net-work of minute veins (rete canalis hypoglossi) traverses the hypoglossal canal and joins the transverse sinus with the vertebral vein and deep veins of the neck.

(4) An inconstant condyloid emissary vein passes through the condyloid canal and connects the transverse sinus with the deep veins of the neck.

(5) A net-work of veins (rete foraminis ovalis) unites the cavernous sinus with the pterygoid plexus through the foramen ovale.

(6) Two or three small veins run through the foramen lace rum and connect the cavernous sinus with the pterygoid plexus.

(7) The emissary vein of the foramen of Vesalius connects the same parts.

(8) An internal carotid plexus of veins traverses the carotid canal and unites the cavernous sinus with the internal jugular vein.

(9) A vein is transmitted through the foramen cecum and connects the superior sagittal sinus with the veins of the nasal cavity.

DIPLOIC VEINS:

The diploic veins occupy channels in the diploĂŤ of the cranial bones. They 1 are large and exhibit at irregular intervals pouch-like dilatations; their walls are thin, and formed of endothelium resting upon a layer of elastic tissue.

So long as the cranial bones are separable from one another, these veins are 2 confined to the particular bones; but when the sutures are obliterated, they unite with each other, and increase in size. They communicate with the meningeal veins and the sinuses of the dura mater, and with the veins of the pericranium. They consist of (1) the frontal, which opens into the supraorbital vein and the superior sagittal sinus; (2) the anterior temporal, which is confined chiefly to the frontal bone, and opens into the sphenoparietal sinus and into one of the deep temporal veins, through an aperture in the great wing of the sphenoid; (3) the posterior temporal, which is situated in the parietal bone, and ends in the sigmoid sinus, through an aperture at the mastoid angle of the parietal bone or through the mastoid foramen; & also communicates with the occipital vein and (4) the occipital, the largest of the four, which is confined to the occipital bone, and opens either externally into the occipital vein, or internally into the transverse sinus or into the confluence of the sinuses (torcular Herophili).

Veins of the diploe SPREAD OF INFECTION THROUGH VENOUS DRAINAGE CONNECTIONS BETWEEN EXTRACRANIAL VEINS & INTRACRANIAL VEINS:

There are 4 ways by which extracranial veins communicate with the intracranial veins.

1. Emissary veins 2. Diploic veins 3. Venous plexus surrounding internal carotid artery & cranial nerves 4. Through superior ophthalmic vein or facial vein and retromandibular vein.

As already mentioned there are various 1.emissary veins found in the head & neck region, but the most important of our concern is the connection between pterygoid plexus & cavernous sinus through foramina ovale , foramina lacerum , & sphenoidal foramina.

Pterygoid plexus of veins is drained by posterior superior alveolar vein which drains the posterior part of the maxilla,so infection from this region can directly enter into cavernous sinus through the pterygoid plexus Facial vein through the deep facial vein communicates with the pterygoid plexus.

2. Diploic veins: Four diploic veins are present Frontal diploic vein- connects to superior sagittal sinus & to the frontal vein Anterior temporal vein- connects to sphenoparietal sinus & deep temporal vein Posterior temporal vein – connects to sigmoid sinus &to the occipital vein Occipital diploic vein- connects to transverse sinus & to the occipital veins 3. venous plexus : The veins that connect the sinuses & the extracranial veins along the internal carotid artery & many of the cranial nerves are loosely connected with the surrounding tissue & therefore collapsible. This acts as compressible cushioning allowing for the changes in the volume of the artery during its pulsation.

The internal carotid plexus of veins connects the cavernous sinus with the pterygoid plexus of veins . another important plexus of vein accompanies the hypoglossal nerve through the hypoglossal canal.

5. Of all the communications , those established by the ophthalmic veins are of greatest clinical importance

There are two types of propagation of a facial thrombophlebities to the cavernous sinus .one path leads from the facial vein into the superior ophthalmic vein or sometimes rarely into the inferior ophthalmic vein which in turn passes through the superior orbital fissure. Second path leads from the retromandibular vein into the pterygoid venous plexus ,from here through the inferior orbital fissure into the terminal part of the inferior ophthalmic vein , & then immediately through the superior orbital fissure into yhe cavernous sinus.

In the first path, there will be warning signals like involvement of orbital or retro bulbar cellulitis in the second pathway , there will be no warning signal directly meningeal symptoms may occur.

Facial & retromandibular veins communicate by deep as well as by superficial anastomoses. The anterior region of the upper jaw drains into the infraorbital veins , which anastomoses freely with the tributaries of the facial vein at the infraorbital foramen , where as infra orbital vein itself enters into the pterygoid plexus draned by retromandibular vein.

The posterior part of the upper jaws drains mainly into the posterior superioralveolar veins which are also tributaries of the pterygoid plexus of veins Venous blood of the lower jaw is primarily drained into the inferior alveolar vein . a branch of the maxillary vein which drains into the retromandibular vein & there is also wide anastomoses between the inferior alveolar vein & tributaries of the facial vein through the mental foramen.

Facial & retromandibular veins are also in direct communication by the veins of the cheek which drains forward to the facial vein & backward to the retromandibular vein.

Spread of infection through the facial vein: The facial vein makes clinically important connections with the cavernous sinus through the superior ophthalmic vein, the pterygoid plexus ,a network of small veins within the infratemporal fossa through the inferior ophthalmic &deep facial veins. Because of these connections, an infection of the face may spread to the cavernous sinus &pterygoid venous plexus.

Blood from the medial angle of the eye, nose, &lips usually drains inferiorly through the facial vein, especially when a person is erect, & as facial vein

has no valves blood may pass through it in the opposite direction consequently, venous blood from the face may enter the cavernous sinus.

In individuals with thrombophlebitis of the facial vein, pieces of infected clot may extend into the intracranial venous system & produces thrombophlebitis of the cavernous sinus.

Infection of the facial vein spreading to dural venous sinuses may result from the lacerations of the nose or be initiated by pimples on the side of the nose &upper lip, consequently the triangular area from the upper lip to the bridge of the nose is considered the danger area of the face.

CAVERNOUS SINUS THROMBOSIS: It is a serious complication of infections of the upper &lower face & neck region .it is more likely to be involved in the potentially fatal spread of infection.each cavernous sinus communicates with each other, with pterygoid plexus of veins,& superior ophthalmic vein which anastomoses with the facial vein.these major veins drain teeth through the posterior superior &inferiorvein & lips through the superior & inferior labial veins.none of the veins that communicate with the cavernous sinus have valves to prevent the retrograde blood flow back into the cavernous sinus

,therefore dental infection that drain through this major veins initiate the inflammatory respone resulting in blood stasis ,thrombus formation,& increasing extra vascular fluid pressure. Increased pressure can change the direction of blood flow,enabling the transport of this thrombus into the venous sinuses causing cavernous sinus thrombosis.

Needle track contamination can also result in spread of infection through pterygoid plexus of veins while administrating posterior superior alveolar block incorrectly.non odontogenic infections originating from the danger triangle of face i.e orbit , nasal region & para nasal sinus.

Signs & sympthoms of cavernous sinus thrombosis:  Fever,  Pappiloedema  Proptosis  opthalmoplegia  Drowsiness,  Rapid pulse,  Loss of function of abducent nerve,  Diplopia,  Edema of eyelids, conjunctiva,  Exopthalmos, depending on the infection  Damage to other cranial nerves, like occulomotor &trochlear as well as ophthalmic &maxillary division  Meningitis.

Most common sites of primary infection1. Facial infection: medial third of face around the eyes & nose Ophthalmic vein.

2 .sphenoid & ethmoid sinus infection- emissary veins & superior ophthalmic vein.

3. Dental infection – pterygoid plexus of veins.

4. Otitis media & complication- mastoiditis REFERENCES1. Clinical Anatomy for medical students- Richard S. Snell, sixth edition.

2. Clinically Oriented Anatomy- Keith L. Moore, Arthur F.Dalley, fifth edition.

3. Gray’s Anatomy- Henry Gray, thirty ninth edition.

4. Last’s Anatomy regional & applied- Chummy S. eleventh edition.

Sinnatamby,

5. The Anatomical Basis Of Dentistry- Bernard Liebgott, second edition page no 394-395 6. Unusual Venous Drainage Pattern of Face: A Case Report. Mehra,S. Kaul J.M. and Das S. J Anat. Soc. India 52(1) 64-65 (2003)