Head Anatomy - V.Z. Sikora 2007

Topographical Anatomy

From the perspective of Topographical Anatomy, the HEAD is divided into two regions: the cerebral (neurocranium) and the facial (viscerocranium). They are demarcated by a line running from the glabella along the supraorbital margin and the zygomatic arch to the external acoustic meatus.

The cerebral part is subdivided into the cranial vault and the cranial base. The vault comprises the frontoparietooccipital region (unpaired) along with the paired temporal and mastoid regions. The facial part is divided into anterior and lateral regions. The anterior region contains the orbital, nasal, oral, and mental regions. The lateral region includes the parotid-masseteric and buccal regions (Fig. 43).

Frontoparietooccipital region

Boundaries:

✵ anteriorly — the supraorbital margin of the Frontal bone;

✵ posteriorly — the external occipital protuberance and the superior nuchal line;

✵ laterally — the superior temporal line.

Layers:

The Skin is thick, Hair-bearing, and contains sweat and Sebaceous Glands. Obstruction of the sebaceous gland ducts leads to The formation of atheromas, which frequently become suppurated, while inflammation of the hair follicles results in furuncles and carbuncles. Due to vertically oriented Connective Tissue septa, the skin firmly adheres to the subcutaneous layer, the m. epicranius, and the epicranial aponeurosis. These connective tissue septa divide the subcutaneous layer into separate Cells filled with lobules of adipose tissue. Consequently, hematomas in this region appear as localized swellings (Fig. 44).

The subcutaneous layer of the frontal region contains the a. supratrochlearis and a. supraorbitalis, which are Branches of the a. ophthalmica originating from the Internal Carotid Artery system.

The a. supratrochlearis emerges from the Orbit through the incisura frontalis into the frontal region at the intersection of the margo supraorbitalis with a vertical line drawn through the medial angle of the eye.

The supraorbital artery (a. supraorbitalis) exits the orbit through the foramen (or incisura) supraorbitalis at the boundary of the middle and medial thirds of the margo supraorbitalis. The a. supraorbitalis and a. supratrochlearis anastomose with each other and with the a. temporalis superficialis (from the a. carotis externa system). Venous Blood drainage occurs via Veins OF THE same name that empty into the v. angularis.

The vessels are accompanied by NERVES OF THE same name, specifically branches of the n. frontalis derived from the n. ophthalmicus, which innervate the skin of this area. The rr. temporales from the n. facialis also pass here, innervating the venter frontalis m. epicranius and the m. orbicularis oculi; therefore, their damage causes lagophthalmos ("hare's eye"), where the eye remains open and tearing is observed.

Efferent Lymphatic vessels from the frontal region drain into the nodi lymphatici parotidei superficialis et profundi (Fig. 45).

In the parietal region, the subcutaneous layer contains:

A. temporalis superficialis — the terminal branch of the External Carotid Artery. It is located anterior to the tragus of the auricle, where it can be compressed against the bone for temporary cessation of bleeding.

V. temporalis superficialis accompanies the artery of the same name. It empties into the v. retromandibularis and receives the v. emissaria parietalis.

N. auriculotemporalis, a branch of the n. mandibularis, accompanies the superficial temporal artery and is located anterior to the vessels.

Lymph drainage occurs into the nodi lymphatici retroauricularis (Fig. 46).

In the subcutaneous layer of the occipital region run the a. auricularis posterior and a. occipitalis, which are branches of the posterior group of the external carotid artery.

The a. auricularis posterior is projected onto the skin along the posterior attachment margin of the auricle.

The a. occipitalis is projected at the midpoint of the distance between the mastoid process and the external occipital protuberance.

The Arteries are accompanied by veins of the same name that drain into the v. jugularis externa.

The skin of the occipital region is innervated by the greater and lesser occipital nerves.

N. occipitalis major, the dorsal ramus of the second cervical nerve, accompanies the occipital artery.

The lesser occipital nerve, originating from the Cervical plexus, runs 3 cm posterior to the attachment of the auricle. At the level of the mastoid process, it lies near the posterior border of the sternocleidomastoid Muscle.

The posterior auricular nerve, a branch of the Facial Nerve, courses within the subcutaneous layer posterior to the auricle, supplying the muscle of the same name and the occipital belly of the epicranial muscle.

Efferent lymphatic vessels drain into the occipital Lymph Nodes (Fig. 47).

Focusing on the Specific features of the region's blood supply, the following points should be noted:

1 The presence of numerous anastomoses among the aforementioned arteries promotes efficient regeneration of damaged Tissues. Consequently, scalp wounds heal significantly faster than those in other PARTS OF THE body with a poorer blood supply. This circumstance also facilitates the engraftment of avulsed scalp flaps of soft tissues.

2 The Blood supply to the area is derived from branches of the internal and external carotid arteries. Thanks to anastomoses between the branches of these vessels, in the event of compromised cerebral perfusion via the primary pathway, a collateral pathway forms, allowing blood to flow from the external carotid artery into the internal carotid artery, which supplies the Brain. Normally, Blood flow through the supratrochlearis artery is directed away from the cranium and into the external carotid system. In cases of stenosis or occlusion of the internal carotid artery, this direction becomes predominantly retrograde. This can be clearly observed using Doppler Ultrasonography, which determines the direction of blood flow.

3 The vessels course within the subcutaneous layer superficial to the aponeurosis, making them highly susceptible to trauma.

4 The adventitia of the vessels is anchored to fibrous septa; therefore, when the vault of the Skull is injured, the vessels do not collapse (they remain patent) and cause severe Hemorrhage.

5 The vessels run radially, extending from the periphery toward the vertex. This factor must be taken into account when making incisions in the soft tissues.

6 A damaged vessel does not protrude into the wound, making it difficult to grasp with standard hemostatic forceps. For this purpose, specialized neurosurgical forceps with tapered tips are used: one tip is applied to the edge of the aponeurotic helmet, and the other to the vessel wall.

Regarding venous drainage, It is important to note that the veins of the head are arranged in three tiers:

I Superficial tier — veins of the integument, which accompany the corresponding arteries. They provide venous drainage into the facial, retromandibular, and external jugular veins.

II Middle tier — intraosseous. These are the diploic veins located within the spongy bone of the cranial vault.

III Deep tier — intracranial. These are the venous sinuses situated between the two layers of the dura mater.

All three tiers are interconnected via emissary veins (venae emissariae).

The largest of these are: the parietal emissary vein, which connects the superior sagittal sinus with the superficial temporal vein; the occipital emissary vein, which connects the transverse sinus with the occipital veins; and the mastoid emissary vein, which connects the sigmoid sinus with the posterior auricular vein.

The connections between the superficial and deep veins facilitate cerebral venous drainage during periods of elevated intracranial pressure or when outflow through the primary pathway is obstructed. At the same time, this may promote the spread of infection—arising from injuries or soft tissue Diseases of the scalp (such as furuncles)—into the bone, leading to Osteomyelitis, or to the dura mater, resulting in meningitis, brain abscess, sinus thrombosis, etc. Such retrograde (i.e., reverse) blood flow and subsequent spread of infection are possible due to the absence of Valves in the veins of the head.

The next layer is the epicranial muscle, whose frontal and occipital bellies are joined by the epicranial aponeurosis. This layer is firmly connected to the skin by connective tissue septa. Thus, the skin, subcutaneous layer, and epicranial aponeurosis form a single functional unit and constitute the components of avulsed scalp flaps.

Beneath the epicranial aponeurosis lies the subaponeurotic layer, which lacks septa. Because of the strong attachment of the skin to the epicranial aponeurosis on one hand, and the loose connection between the epicranial aponeurosis and the periosteum on the other, scalping injuries can occur in the cranial vault region. Hematomas and purulent processes in the subaponeurotic layer present as diffuse Swelling and occupy the entire surface of the cranial vault.

The next layer is the periosteum. It is firmly attached to the bone in the region of the sutures and loosely connected elsewhere. During surgical interventions, the periosteum must be handled with great care because it contains the vessels that nourish the outer table (lamina externa). Slightly deeper than the periosteum lies the subperiosteal layer, which allows the periosteum to be easily detached, while hematomas are bounded by the lines of the bone sutures and remain confined to a single bone. Subperiosteal hematomas impair the blood supply to the bones and can lead to Necrosis of the outer table of the cranial vault; therefore, they require prompt removal. All fascial spaces of the fronto-parieto-occipital region communicate with one another via anastomoses of the external veins, the dural sinuses, and the diploic veins through emissary veins, potentially serving pathways for the spread of inflammatory processes.

The bony foundation of the region is formed by the frontal, occipital, and two parietal bones, tightly joined together by syndesmoses (sutures). These are flat bones; their external surface is smooth with numerous vascular foramina. The internal surface is rough, featuring grooves and depressions corresponding to adjacent arteries, Dural Venous Sinuses, arachnoid granulations, and cerebral gyri.

The cranial bones consist of three layers: the outer table (lamina externa), composed of compact Bone tissue; the middle layer (diploe or spongy layer), inside the canals of which (canals of Breschet) the diploic veins (vv. diploicae) are located.

In skull fractures involving these veins, significant hemorrhage frequently occurs, to stop which Special Methods are employed (nibbling the bone edges, rubbing in wax- or paraffin-based bone wax, and plugging with bone fragments).

The third layer is represented by the inner table (lamina interna). It is thinner and more brittle, and is therefore termed the glassy table (lamina vitrea). During head trauma, it is damaged more frequently than the outer table and tends to produce bone fragments that often lacerate the dural vessels and brain tissue, leading to the formation of epidural and subdural hematomas. Cranial bones regenerate slowly; consequently, bone defects can always be observed on radiographs at the site of a former fracture.

In the frontal region, the frontal sinus is located between the outer and inner tables.

It should be taken into account that frontal wounds involving bone damage can be secondary infected from the Nasal cavity.

Temporal region

Boundaries:

✵ superiorly and posteriorly: superior temporal line;

✵ inferiorly: zygomatic arch;

✵ anteriorly: frontal process of the Zygomatic bone and zygomatic process of the frontal bone.

Layers:

The skin is thin, hair-bearing, and innervated by the auriculotemporal nerve, zygomaticotemporal nerve, and lesser occipital nerve. The subcutaneous layer is scanty and contains:

The anterior and superior auricular Muscles, which are innervated by the temporal branches of the facial nerve.

The superficial temporal artery, accompanied by the corresponding vein and the auriculotemporal nerve.

Near the lateral orbital margin runs the zygomaticotemporal nerve, a branch of the zygomatic nerve arising from the maxillary nerve. Posterior to the auricle lie the posterior auricular artery (a branch of the external carotid system), the corresponding vein, and the lesser occipital nerve.

The superficial fascia represents a continuation of the epicranial aponeurosis and appears as a thin sheet. It forms a fascial sheath for the auricular muscles, vessels, and nerves.

The deep fascia, or temporal aponeurosis, splits into superficial and deep layers before reaching the zygomatic arch. The superficial layer attaches to the outer margin of the zygomatic arch, while the deep layer attaches to its inner margin.

Between these layers lies the interaponeurotic temporal space, within the fatty tissue of which run the middle temporal artery, the corresponding vein, and the zygomaticotemporal nerve.

Beneath the Deep Layer of the deep fascia, directly over the temporalis muscle, lies the Third Layer of adipose tissue—the subaponeurotic fat pad, which continues inferiorly past the zygomatic arch into the buccal fat pad (of Bichat). Hematomas and suppurations of the subaponeurotic space can track downward into the lateral facial region and vice versa.

The temporalis muscle fills the temporal fossa and inserts into the coronoid process. Deep to the temporalis muscle lies the deep osteomuscular fascial space of the temporal region. It contains the deep temporal Vessels and nerves: the deep temporal artery (a branch of the maxillary nerve) and the deep temporal nerve (a branch of the mandibular nerve). Deeper still is the periosteum, beneath which lies the subperiosteal layer. Although poorly developed, it can become involved in the inflammatory process during deep phlegmons of the temporal region. Pus from deep phlegmons may extend inferiorly into the infratemporal and pterygopalatine fossae, and subsequently reach the orbit via the inferior orbital fissure, communicating with the temporopterygoid space of the lateral facial region.

The bony framework of the region is formed by the greater wing of the Sphenoid bone, the squamous part of the Temporal bone, and small portions of the frontal and parietal bones. Spongy bone is poorly developed and entirely absent in the squamous temporal bone. On the inner surface of the squamous temporal bone runs the arterial sulcus, which lodges the middle meningeal artery. Injury to this artery can lead to the formation of epidural hematomas.

Mastoid region

Boundaries:

✵ anteriorly: line of attachment of the auricle;

✵ superiorly: line corresponding to the posterior extension of the zygomatic arch;

✵ inferiorly and laterally: outline of the mastoid process, which is palpable through the skin.

Layers:

The skin is thin, hairy in the posterior part of the region, and tightly adherent to the underlying tissues.

The subcutaneous layer contains: the posterior auricular artery, posterior auricular vein, Lymphatic vessels and nodes (lymph nodes that drain lymph from the auricle and parietal region), and the posterior auricular muscle, which is innervated by the posterior auricular branch of the facial nerve.

The superficial fascia forms a sheath for the posterior auricular muscle.

The deep fascia represents a continuation of the epicranial aponeurosis. It extends downward to the neck, where it forms sheaths for the sternocleidomastoid muscle, trapezius muscle, and the posterior belly of the digastric muscle. Between the trapezius muscle and the posterior belly of the digastric muscle lies a fascial-cellular cleft that continues into the lateral triangle of the neck and the Sheath of the sternocleidomastoid muscle, potentially serving as a pathway for the spread of pus in Bezold's mastoiditis. This condition manifests as swelling and tenderness in the cervical region.

The periosteum is tightly fused with the bone, particularly at the sites of muscle attachments (sternocleidomastoid muscle, splenius capitis muscle, longissimus capitis muscle, and posterior belly of the digastric muscle).

The subperiosteal layer is poorly developed.

The mastoid process of the temporal bone is located posterior and inferior to the external acoustic meatus. It is cone-shaped, with its base directed superiorly, and its lateral surfaces are rough. In the middle lies a smooth area known as Shrapnel's trepanation triangle. The triangle is bounded: anteriorly, by a vertical line drawn along the posterior margin of the external acoustic meatus from the apex of the mastoid process through the suprameatous spine (Henle's spine); posteriorly, by the mastoid crest, crista mastoidea (the site of attachment of the sternocleidomastoid muscle); and superiorly, by a horizontal line representing the continuation of the zygomatic arch (Fig. 48).

Inside the mastoid process, there are bony air cells (cellulae mastoideae), the upper part of which forms the mastoid antrum, or antrum mastoideum. Through the aditus ad antrum, the antrum communicates with the tympanic cavity, opening into the epitympanic recess (recessus epitympanicus). The latter houses the head of the malleus and the incus.

All mastoid air cells open into the mastoid antrum. The mastoid cells are lined with a mucous membrane that extends here from the tympanic cavity.

Thus, the tympanic cavity and its accessory cavities form a single pneumatized system filled with air via the auditory (Eustachian) tube, or tuba auditiva.

During inflammation of the Middle ear (otitis media), inflammatory exudate cannot escape through the internal opening of the auditory tube because the latter is relatively narrow and its margins adhere to one another As a result of mucosal edema. Consequently, a closed space is formed within the middle ear cavity, where purulent exudate accumulates. With significant accumulation, the exudate is directed through the aditus ad antrum into the antrum and spreads through the mastoid air cells, resulting in mastoiditis. Pus can be evacuated from the middle ear through the posterior wall of the tympanic cavity by opening the mastoid antrum, which is projected within the boundaries of Shrapnel's triangle.

The lateral wall of the mastoid antrum is approximately 1.5–2 cm thick. The medial wall separates the antrum from the sigmoid sulcus and the underlying sigmoid sinus. The superior wall of the mastoid antrum is a continuation of the tegmen tympani (roof of the tympanic cavity) and separates the latter from the middle cranial fossa. Slightly anterior to the antrum lie the lateral semicircular canal and the facial nerve.

Thus, purulent exudate from the tympanic cavity can penetrate into the mastoid antrum and further—by damaging the medial wall of the mastoid antrum—into the cranial cavity or the sigmoid sinus, causing life-threatening complications such as meningitis, Sepsis, and sigmoid sinus thrombophlebitis. Clinically, this manifests as MacEwen's syndrome (dysphagia, aphonia, Torticollis) resulting from damage to the 9th, 10th, and 11th pairs of Cranial Nerves.

In all of the aforementioned cases, trepanation of the mastoid process is performed. Pus may penetrate into the bed of the sternocleidomastoid muscle and the region of the lateral triangle of the neck (Bezold's mastoiditis), leading to the formation of deep neck phlegmons.

Meninges of the Brain

The cranial cavity is lined internally by the cranial dura mater, which is easily detached from the BONES OF THE cranial vault and firmly fused with the bones of the cranial base. Therefore, in head trauma, epidural hematomas are more common in the region of the cranial vault.

The dura mater consists of two layers, between which lies a thin tissue layer containing Blood Vessels and nerves. This structural feature of the dura mater was utilized by N. N. Burdenko to repair defects in vascular sinus injuries.

Processes extend from the dura mater: the falx cerebri, tentorium cerebelli, and falx cerebelli. These processes penetrate the fissures of the brain, separating its parts from one another.

The tentorium cerebelli is situated in a horizontal plane. It projects into the transverse cerebral fissure, separating the occipital lobes from the Cerebellum. It attaches along the margins of the transverse sinus sulcus, along the superior edge of the petrous parts of the temporal bones, and reaches the anterior clinoid processes of the sphenoid bone. The anterior, free margin of the tentorium cerebelli features the tentorial notch (incisura tentorii) in the middle, through which the Brainstem passes. Herniation (displacement) of the cerebrum into the tentorial notch can occur in cases of a sharp drop in CEREBROSPINAL FLUID pressure, leading to compression of the brainstem, where vital respiratory and circulatory (cardiovascular) centers are located. Therefore, draining a large volume of cerebrospinal fluid during lumbar punctures is discouraged.

Venous sinuses, which drain venous blood from the brain, are located within the dural folds.

The sinuses are closely connected with diploic veins, as well as the external veins of the cranial vault and base. The sinus walls are dense, tightly stretched, and devoid of valves. This structural feature ensures the unhindered drainage of venous blood from the brain regardless of intracranial pressure fluctuations. When injured, the sinus walls gape and do not collapse, causing severe hemorrhage. Consequently, the superior sagittal sinus and cavernous sinus are of particular importance to neurosurgeons.

The superior sagittal sinus is located along the superior margin of the falx cerebri, extending from the frontal crest of the frontal bone to the internal occipital protuberance within the matching sulcus of the cranial vault, and empties into the transverse sinus, most commonly the right one. The superior sagittal sinus communicates with the nasal veins via the foramen cecum. Therefore, chronic inflammatory processes in the nasal cavity can potentially lead to the spread of infection to the superior sagittal sinus. Through the parietal emissary vein, it connects with the superficial temporal vein, and via Trolard's vein, it communicates with the cavernous sinus.

On either side of the superior sagittal sinus, between the layers of the dura mater, lie lateral lacunas (blood lakes), which are small venous cavities communicating with the lumen of the sinus. Dural veins, superior cerebral veins, diploic veins, and arachnoid granulations empty into these lateral lacunas. Deviations of the sinus to the right or left, branching of the sinus, and the presence of blood lakes must be taken into account during Craniotomy or burr hole placement.

At the Base of the skull, to the right and left of the sella turcica, lies the paired cavernous sinus. Both sinuses are interconnected by the anterior and posterior intercavernous sinuses. As a result, the circular sinus (Ring of Ridley) is formed in the region of minder sella turcica.

The cavernous sinus receives blood from the ophthalmic veins—the superior and inferior ophthalmic veins—which drain blood from the frontal region, nasal cavity, Eyeball, and sphenoparietal sinus. Through the ophthalmic veins, the cavernous sinus communicates with the pterygoid venous plexus and facial veins. Specifically, the superior ophthalmic vein anastomoses with the facial veins via the angular vein, while the inferior ophthalmic vein connects with the deep facial vein, which links the pterygoid plexus to the facial vein. Additionally, the cavernous sinus communicates with the pterygoid plexus through the venous plexus of the oval foramen and the emissary vein of the lacerum foramen.

The presence of these connections explains the rapid spread of infection from the soft Tissues of the head into the cavernous sinus, leading to severe complications such as Purulent meningitis, sepsis, and brain abscess.

In cross-section, the cavernous sinus is triangular in shape. Its superior wall transmits the Oculomotor nerve and Trochlear nerve. Its lateral wall transmits the ophthalmic nerve. The Abducens nerve and internal carotid artery pass through the sinus itself.

Cavernous sinus thrombosis results in Foix syndrome, characterized by complete ophthalmoplegia (paralysis of the extraocular muscles) due to damage to the III, IV, and VI cranial nerve pairs. Clinical manifestations include exophthalmos (protrusion of the eyeball), eyelid edema, ptosis (drooping of the upper eyelid), and immobility of the eyeball. Sinus involvement is accompanied by pulsating exophthalmos. The cavernous sinus communicates with the superior sagittal sinus and transverse sinus via the veins of Trolard and Labbé. The vein of Trolard (v. anastomotica superior) connects the superficial middle cerebral vein (v. cerebri media superficialis) with the superior sagittal sinus, whereas the vein of Labbé (v. anastomotica inferior) connects the superficial middle cerebral vein with the transverse sinus. The presence of these vascular anastomoses makes ligation of the posterior segments of the superior sagittal sinus clinically feasible.

The primary source of blood supply to the dura mater is the middle meningeal artery (a. meningea media, a branch of the maxillary artery). It enters the cranial cavity through the foramen spinosum, courses along the cerebral surface of the greater wing of the sphenoid bone, the Parietal bone, and the squamous part of the temporal bone within a dedicated bone groove (sulci a. meningeae). The artery divides into frontal (anterior) and parietal (posterior) branches.

The anterior branch courses superiorly, forming an arch with an anterior convexity, while the posterior branch courses posteriorly and superiorly, or occasionally takes a horizontal course as an anatomical variant (Fig. 49).

The artery runs within the thickness of the dura mater, closer to its external layer. Because the vessel is difficult to grasp with a hemostatic clamp, injury to this artery requires ligation of both ends along with suturing of the outer and inner dural layers beneath the vessel. The artery is accompanied by two veins. The anterior branch, or the artery itself at the pterion (the junction of the frontal, parietal, temporal, and sphenoid bones), is lodged within a bone canal. This anatomical feature must be taken into account when drilling burr holes during craniotomy.

Trauma to the middle meningeal artery and its branches frequently leads to the formation of epidural and subdural hematomas.

The course of the anterior branch corresponds to THE POSITION OF the precentral sulcus, which houses the motor centers of the Cerebral Cortex, whereas the course of the posterior branch corresponds to the Location OF THE temporal lobe. These anatomical landmarks are crucial for the Diagnosis of epidural hematomas. As a result of cranial vault fractures, blood accumulates between the bone and the dura mater, stripping the latter from the bone and compressing the brain, thereby eliciting focal neurological signs.

The indicators of an intracranial hematoma include:

1 Mydriasis – dilation of the pupil on the side of the hematoma, resulting in anisocoria (unequal pupil size of the right and left eyes); the underlying cause is brain injury combined with the impairment of parasympathetic fibers traveling within the III cranial nerve pair. Mydriasis is accompanied by ptosis (drooping of the upper eyelid).

2 Hemiparesis – weakness of the muscles on one side of the body contralateral to the hematoma. This is caused by compression of the motor cortex and the crossing of the Pyramidal Tracts to the opposite side at the level of the Medulla Oblongata.

3 Bradycardia – a decreased Heart rate per minute. It occurs as a result of brainstem trauma, cerebral edema and Hypoxia, and increased vagal tone.

4 The presence of a "lucid interval." As the hematoma expands, consciousness progressively deteriorates.

Innervation of the cranial dura mater is supplied by branches of the Trigeminal nerve (the tentorial branch from the ophthalmic nerve, the middle meningeal branch from the maxillary nerve, and the meningeal branch from the mandibular nerve, which enters the cranial cavity through the foramen spinosum), as well as the meningeal branch of the Vagus nerve, which enters the cranial cavity through the jugular foramen.

The arachnoid mater of the brain lies directly beneath the dura mater. The subdural space (spatium subdurale) is situated between the arachnoid and dura mater. It contains superficial cerebral veins that drain into the dural venous sinuses. Injury to these veins results in subdural hematomas. Unlike epidural hematomas, subdural hematomas are more diffuse and develop gradually. The arachnoid mater is a thin, translucent membrane that envelops the brain without extending into the sulci. It bridges across cerebral gyri, forming the subarachnoid space with the deeper pia mater, which contains cerebrospinal fluid.

The total volume of cerebrospinal fluid (CSF) in adults ranges from 100 to 150 ml. The CSF pressure in the recumbent position is 120–150 mm H₂O. When measured in the sitting position, it reaches 200–250 mm H₂O. Cerebrospinal fluid pressure and composition are evaluated via lumbar puncture. To assess the patency of the subarachnoid space of the BRAIN AND SPINAL cord in cases of tumors or other conditions causing compression, CSF manometric tests are performed: the Queckenstedt test (compression of the internal jugular veins increases CSF pressure 2- to 3-fold) and the Stookey test (compression of the INFERIOR VENA CAVA through the anterior abdominal wall leads to spinal venous congestion, increasing pressure 1.5- to 2-fold).

A negative result in these tests, meaning an absence of pressure elevation, indicates the presence of a pathological process.

In the Queckenstedt test, compression of one jugular valve may lead to a pressure rise, whereas compression of the other does not. In such cases, there is an obstruction of the jugular vein, transverse sinus, or sigmoid sinus on the side where the pressure fails to rise.

The majority of cerebrospinal fluid is produced by the choroid plexuses of the Lateral ventricles of the cerebrum. From the lateral ventricles, CSF flows into the III ventricle through the interventricular foramina (foramina interventricularia [Monro]). From the cavity of the III ventricle, it passes through the cerebral aqueduct (aqueduct of Sylvius) into the IV ventricle. From the IV ventricle, it flows through apertures in the tela choroidea—the median aperture (foramen of Magendie) and the lateral apertures (foramina of Luschka)—into the cerebellomedullary cistern, which is directly continuous with the subarachnoid space of the Spinal Cord.

Excessive accumulation of cerebrospinal fluid within the cranial cavity is termed Hydrocephalus. It may arise as a result of impaired CSF outflow due to various pathologies (tumors, inflammatory processes, etc.); very frequently, it results from birth trauma.

Lateral region of the face

Boundaries:

✵ superiorly – the zygomatic arch and the inferior orbital margin;

✵ inferiorly – the inferior border of the base of the Mandible;

✵ anteriorly – the nasolabial and nasofacial sulci;

✵ posteriorly – the posterior border of the mandibular ramus.

By means of a line drawn along the anterior border of the masseter muscle, the lateral facial region is further subdivided into the buccal and parotid-masseteric regions.

Buccal region

Layer-by-layer Anatomical Characteristics.

The skin is thin and mobile, containing a high density of sweat and sebaceous glands, as well as an abundant network of Blood and Lymphatic vessels and nerve endings.

The subcutaneous layer contains the facial muscles, the facial artery and vein, branches of the trigeminal and facial nerves, lymphatic vessels, and the duct of the Cytology/practical/97.html">Parotid salivary gland (Fig. 50).

The superficial fascia forms fascial sheaths for the facial muscles and the neurovascular structures of the face.

The facial muscles originate from the bones and insert into the skin, forming folds and wrinkles that serve as important landmarks during surgical interventions. When performing facial surgeries, skin incisions should be made parallel to these folds to ensure that postoperative scars remain barely noticeable.

The facial artery and vein are located between the facial muscles.

The facial artery emerges onto the face near the anterior border of the masseter muscle, winding around the lower border of the mandible. Here, it can be compressed against the bone to temporarily stop bleeding during facial injuries. The artery courses toward the angle of the Mouth, running about 1–2 cm lateral to it. From there, it ascends to the medial angle of the eye, passing between the buccinator muscle and the zygomatic major muscle; in this section, it is referred to as the angular artery, anastomosing with the dorsal nasal artery from the ophthalmic artery. This forms an anastomosis between two major systems: the external carotid artery system (via the angular artery) and the internal carotid artery system (via the dorsal nasal artery). Along its path, the facial artery gives off branches to the upper and lower Lips (superior and inferior labial arteries). The facial artery is accompanied by the facial vein. The latter begins near the medial angle of the eye as the angular vein, which anastomoses with the superior and inferior ophthalmic veins. Passing over the lower border of the mandible, it joins the retromandibular vein to form the common facial vein, which empties into the Internal jugular vein.

The facial vein communicates via anastomoses with the ophthalmic veins and the cavernous sinus, and through the deep facial vein (of Sesé) with the pterygoid plexus. These anastomoses are of critical clinical importance in the spread of inflammatory processes in the face. When the facial vein or its tributaries undergo thrombosis (thrombophlebitis) or are compressed by an inflammatory infiltrate (such as a furuncle), retrograde blood flow may occur—either from the facial vein into the angular vein and subsequently into the inferior ophthalmic vein and cavernous sinus, or from the facial vein into the deep facial vein and pterygoid plexus, and thence via the emissary vein of the foramen lacerum into the cavernous sinus. Septic emboli entering the cavernous sinus can lead to cavernous sinus thrombosis, meningitis, brain abscess, and sepsis. The prognosis for such complications is extremely grave (Fig. 52).

The deep fascia is a continuation of the temporal aponeurosis and is divided into superficial and deep layers. The superficial layer forms a sheath for the buccal fat pad, while the deep layer of the deep fascia transitions into the buccopharyngeal fascia, continuing onward as the pharyngobasilar fascia. The buccal fat pad (fat pad of Bichat), encapsulated within its own sheath, is located near the anterior border of the masseter muscle. Medial to the buccal fat pad lies the outer surface of the buccinator muscle. Laterally and anteriorly, the parotid duct (Stensen's duct) loops around it, accompanied by the transverse facial artery. The buccal fat pad consists of three portions, from which the temporal, orbital, and pterygopalatine processes extend. The temporal process passes beneath the zygomatic arch and communicates with the subaponeurotic fat space of the temporal region. The orbital process enters the infratemporal fossa, lying adjacent to the inferior orbital fissure, and very frequently communicates with the orbital fat. The pterygopalatine process communicates with the temporopterygoid fascial space and enters the pterygopalatine fossa through the pterygomaxillary fissure, enveloping the maxillary nerve and the pterygopalatine ganglion. Frequently, via the superior orbital fissure, it reaches the internal cranial base, extending as far as the cavernous sinus. Thus, the buccal fat pad connects the fascial spaces of the buccal region with the temporopterygoid space, the subaponeurotic space of the temporal region, and the fascial spaces of the pterygopalatine fossa and orbit. These anatomical pathways play a major role in the spread of inflammatory processes. It is safe to say that the buccal fat pad serves as the primary conduit for purulent-inflammatory processes of the face.

Situated between the Maxilla and mandible is the buccinator muscle, which is covered by the buccopharyngeal fascia. The buccinator originates from the upper and lower jaws and blends with the facial Muscles surrounding the oral fissure. Upon contraction, it pulls the angle of the mouth posteriorly, pressing the cheek against the Teeth. The substance of the muscle is pierced by the excretory duct of the parotid gland, the parotid duct (Stensen's duct), for which the muscle acts as a sphincter. On its inner surface, the muscle is lined by the mucous membrane of the oral vestibule. It is supplied with blood by the buccal artery, a branch of the second part of the maxillary artery. Innervation is provided by the buccal branches of the facial nerve. Consequently, injury to this nerve results in the "sail sign" (Atrophy of the buccinator muscle) and leakage of saliva through the incompletely closed angle of the mouth. The muscle undergoes marked hypertrophy in wind instrument players, which is why it is commonly referred to as the "trumpeter's muscle" (Fig. 52).

Deep to the facial muscles in the buccal region lie the maxilla and mandible, featuring the infraorbital (on the maxilla) and mental (on the mandible) foramina, through which the corresponding vessels and nerves emerge into the soft tissues (Fig. 53).

The infraorbital neurovascular bundle emerges from the corresponding foramen about 0.5 cm below the midpoint of the infraorbital margin into the loose fatty tissue of the canine fossa on the anterior wall of the maxillary sinus.

The infraorbital artery is a branch of the second part of the maxillary artery. The infraorbital vein drains into the inferior ophthalmic vein or the pterygoid plexus.

Infraorbital nerve block anesthesia is administered during surgical interventions on the maxilla, maxillary fractures, and tooth extractions.

The mental neurovascular bundle emerges from the mental foramen of the mandible along the same vertical line as the supraorbital and infraorbital foramina.

The areas of referred pain upon Palpation along the projection Zones of the branches of the trigeminal nerve are known as "Valleix points" (or Valleix's zones).

Lymphatic drainage from the buccal region proceeds to the submandibular and submental lymph nodes. A portion of the lymphatic vessels is interrupted in the buccal lymph nodes located on the outer surface of the buccinator muscle. Inflammation of these nodes can cause compression of the parotid duct and salivary stasis, which is a predisposing factor for The Development of parotitis.

Parotid-masseteric region

Layers:

The skin is thin, fairly mobile, and hair-bearing. In the subcutaneous layer, enclosed within the fascial sheath of the superficial fascia, run the branches of the great auricular nerve, the auriculotemporal nerve, the buccal nerve from the mandibular nerve, branches of the facial nerve, the transverse facial artery, and the zygomaticofacial nerve. Deep to the subcutaneous tissue lies the deep fascia—the parotidomasseteric fascia—which attaches to the zygomatic arch, the lower border, and the angle of the mandible. Near the anterior border of the parotid gland, the fascia splits into two layers, forming a capsule for the gland known as the parotid fascia; this fascia penetrates into the substance of the gland between its lobules, continues over the masseter muscle, and is referred to as the masseteric fascia.

The anterior portion of the region is occupied by the masseter muscle. The muscle originates from the zygomatic bone and zygomatic arch, passes inferiorly, and inserts into the masseteric tuberosity on the lateral surface of the angle of the mandible. Upon contraction, the muscle elevates the mandible and draws it forward (via its superficial fascicles). The muscle is enclosed within an osteofibrous sheath, the Medial surface of which lies adjacent to the mandibular ramus.

Located between the mandibular ramus and the masseter muscle is the submasseteric fascial space, which contains the masseteric nerve, masseteric artery, and masseteric vein. The submasseteric space communicates with the temporopterygoid and interpterygoid spaces, as well as with the buccal fat pad. Phlegmonous infections can develop here. Medial to the masseter muscle lies the ramus of the mandible. Its condylar process participates in the Formation of the temporomandibular joint. The components directly involved in forming this joint include the head of the mandible, along with the mandibular fossa and the articular tubercle of the temporal bone. If the articular tubercle becomes flattened and the mandibular fossa is shallow (changes that occur in elderly individuals following tooth loss), excessive mouth opening—such as during yawning—causes the mandibular head to displace anteriorly, resulting in dislocation of the jaw (Fig. 54).

Situated in the posterior part of the region and in the retromandibular fossa is the parotid salivary gland. This is the largest of the Salivary Glands; structurally, it is a compound, branched alveolar-tubular gland of a serous secretory type. It is surrounded by layers of the parotid fascia and adjacent muscles. Together with the vessels and nerves passing through its substance, it fills the parotid space, which is bounded: anteriorly by the posterior and lateral surfaces of the masseter muscle, the ramus of the mandible, and the medial pterygoid muscle; posteriorly by the sternocleidomastoid muscle, the posterior belly of the digastric muscle, and the mastoid process; inferiorly by the Submandibular salivary gland; and medially by the styloid process of the temporal bone, the muscles of Riolan's bouquet arising from it (the stylohyoid, styloglossus, and stylopharyngeus muscles), and the fatty tissue of the anterior compartment of the parapharyngeal space.

In this area, the parotid space is not completely closed. The pharyngeal process of the parotid gland occupies the gap between the styloid process and the medial pterygoid muscle, lacking a distinct fascial covering (representing a weak spot in the glandular capsule), and lies in close proximity to the anterior portion of the parapharyngeal space. This explains how pus from an inflamed parotid gland can easily track into the parapharyngeal fascial space (Fig. 55).

The subcutaneous Adipose tissue is adjacent to the lateral surface of the parotid gland; superiorly, it is bordered by the cartilaginous part of the external acoustic meatus. The fascial capsule in this area is poorly developed and ruptures during purulent parotitis, which causes the inflammatory process to spread through the Santorini fissures into the external acoustic meatus and the middle ear.

The gland is supplied with blood by the rr. parotidei from the a. temporalis superficialis. Venous blood drainage occurs into the v. retromandibularis. Lymph drainage is directed to the nodi lymphatici parotidei superficialis et profundi.

The gland is innervated by the rr. parotidei from the n. auriculotemporalis. Secretory parasympathetic fibers to the gland pass from the inferior salivatory Nucleus of the IX cranial nerve (n. salivatorius inferior) as part of the n. glossopharyngeus, n. tympanicus, n. petrosus minor to the ganglion oticum (Arnoldi). Postganglionic fibers run within the n. auriculotemporalis to reach the gland. The inferior (petrosal) ganglion of the n. glossopharyngeus, the tympanic nerve, the tympanic plexus, the lesser petrosal nerve, and the otic (Arnold's) ganglion form Jacobson's anastomosis.

The excretory (Stensen's) duct of the parotid gland, ductus parotideus Stenoni, originates from the anterior border of the gland, runs anteriorly, located 1–1.5 cm inferior and parallel to the zygomatic arch along the external surface of the masseter muscle, lies superficial to the buccal fat pad, and, wrapping around the anterior border of the masseter muscle, turns medially, piercing the buccinator muscle. It passes beneath the buccal mucosa, opening via an orifice on the parotid papilla in the Vestibule of the Oral Cavity at the level of the second upper molar. The excretory duct is projected onto the skin of the face along a line drawn from the external acoustic meatus to a point located at the midpoint of the distance between the nasal ala and the angle of the mouth, within the so-called Tsakadze triangle.

The following structures pass through the thickness of the parotid gland: the a. carotis externa, v. retromandibularis, n. auriculotemporalis, and n. facialis.

Within the thickness of the gland, the a. carotis externa divides into its terminal branches: the a. temporalis superficialis and a. maxillaris.

The v. retromandibularis (retromandibular vein) is a continuation of the v. temporalis superficialis. It passes anterior to the auricle, descends posterior to the ramus of the mandible from the lateral surface of the a. carotis externa. It runs toward the angle of the mandible and, inferior to the posterior belly of the m. digastricus, joins the facial vein. Their common trunk—the v. facialis communis—empties into the internal jugular vein.

The n. auriculotemporalis is a branch of the n. mandibularis (the third branch of the V cranial nerve). It originates with two roots that embrace the a. media meningea on both sides and then merge into a single trunk, passing along the medial surface of the articular process of the mandible and penetrating the bed of the gland. Here, it lies medial to the a. temporalis superficialis, which it subsequently accompanies. In patients who have undergone surgery on the parotid gland, the formation of postoperative scars involving the vasomotor fibers of the n. auriculotemporalis leads to auriculotemporal syndrome (or Frey-Baillarger syndrome)—a complex of autonomic-vascular disorders manifested by skin hyperemia and excessive sweating during meals. Neuralgia of the auriculotemporal nerve is characterized by a burning pain in the temporal region, external acoustic meatus, and temporomandibular joint. The pain attack is accompanied by skin hyperemia, hyperhidrosis (excessive sweating), and increased salivation.

Beneath the fascia On the surface of the gland, as well as within the glandular parenchyma itself, lie the nodi lymphatici parotidei superficialis et profundi. They collect lymph from the frontal, temporal, and buccal regions, as well as from the periodontal tissues of the molars.

Facial nerve

The motor nucleus of the VII cranial nerve is located in the ventral part of the tegmentum of the Pons. The axons of the cells of this nucleus emerge from the pons in the cerebellopontine angle region along with the fibers of the intermediate nerve, which carry afferent impulses from the geniculate ganglion. Together, they enter the internal acoustic meatus of the petrous part of the temporal bone and enter the facial canal, which is about 3 cm long. The canal has a bend that houses the sensory geniculate ganglion (ganglion geniculi). The fibers of the geniculate ganglion form the main part of the intermediate (Wrisberg's) nerve. They run together with the motor trunk of the facial nerve and branch off from it as the fibers of the greater petrosal nerve (n. petrosus major). Taste fibers form the chorda tympani. The latter also contains parasympathetic secretory fibers for the submandibular and sublingual autonomic ganglia. The n. petrosus major emerges onto the anterior surface of the petrous part of the temporal bone through the hiatus canalis n. petrosi majoris, passes to the external skull base through the foramen lacerum, and, as part of the vidian nerve, penetrates through the canalis pterygoideus into the pterygopalatine fossa, reaching the ganglion pterygopalatinum.

The chorda tympani emerges from the petrous part of the temporal bone on its inferior surface through the petrotympanic fissure (fissura petrotympanica), joins the n. lingualis, and contains both taste and parasympathetic secretory fibers for the submandibular and sublingual salivary glands. Inflammation of the geniculate ganglion results in geniculate herpes zoster, or Hunt's syndrome. Clinically, it manifests as herpetic eruptions in the area of the external acoustic meatus and auricle, severe deep-seated ear pain radiating to the facial, occipital, and cervical regions, symptoms of facial nerve neuritis, and a decrease in taste sensitivity.

Some of the motor fibers of the facial nerve trunk branch off to the stapedius muscle, while the main trunk emerges from the petrous part of the temporal bone through the stylomastoiding foramen (foramen stylomastoideum) at the level of the attachment of the lower pole of the auricle.

Before entering the glandula parotis, it gives off the posterior auricular nerve (n. auricularis posterior) to innervate the muscle of the same name, the venter occipitalis m. epicranii, as well as the r. stylohyoideus and r. digastricus leading to the posterior belly of the digastric muscle.

Having penetrated the thickness of the parotid salivary gland in its posterosuperior part to a depth of about 2 cm, at the level of the lower circumference of the external acoustic meatus, it divides into radially departing branches that interconnect to form the plexus parotideus.

Due to its appearance, this plexus is known as the "pes anserinus major" (greater goose's FOOT): rr. temporales, rr. zygomatici, rr. buccales, r. marginalis mandibulae, and r. colli.

The upper branch, rr. temporales, is the most consistent in its course and branching pattern. Its projection corresponds to a line connecting the ear lobule and the lateral angle of the eye. The middle branches, rr. zygomatici et rr. buccales, run parallel to Stensen's duct. The marginal mandibular branch (ramus marginalis mandibulae) is the most variable in its course, running 0.5–1 cm below the lower border of the mandible. This anatomical feature must be taken into account when draining submandibular phlegmons.

The close anatomical relationship between the branches of the facial nerve and the parenchyma of the parotid salivary gland explains the occurrence of facial muscle paralysis during inflammation of the gland. Knowledge of the Topography of the facial nerve and its branches is of great practical importance when performing surgical interventions on the parotid gland.

Within the Fallopian canal, the facial nerve lies at a considerable distance from the periosteum. Periostitis can cause compression of the nerve, leading to its ischemia.

A leading factor in the development of peripheral facial nerve paralysis (Bell's palsy) is the impairment of its blood supply.

The main source of blood supply to the facial nerve within the canal is the stylomastoid artery (a. stylomastoidea), a branch of the posterior auricular artery (a. auricularis posterior). Spasm of this artery causes ischemia and degeneration of nerve fibers.

Deep region of the face

This region was designated by N.I. Pirogov as the intermandibular space and can be studied after the removal of the zygomatic arch, the ramus of the mandible, and the temporalis muscle.

The region occupies the infratemporal fossa (fossa infratemporalis) and is bounded by:

✵ anteriorly — the infratemporal surface (facies infratemporalis), maxillary tuberosity (tuber maxillae);

✵ posteriorly: by the parotid gland;

✵ laterally: by the ramus of the mandible, the lower portion of the temporalis muscle, and the zygomatic arch;

✵ medially: by the lateral pterygoid plate;

✵ superiorly: by the greater wing of the sphenoid bone;

✵ inferiorly: by the medial and lateral walls.

The Contents of the deep facial region include the pterygoid muscles (lateral and medial pterygoids). They are surrounded by the pterygoid venous plexus and adipose tissue, through which the maxillary artery and the mandibular nerve pass (Fig. 56).

Two fascial spaces are located in this region: the temporopterygoid space and the interpterygoid space. The temporopterygoid space is bounded: laterally by the temporalis muscle, medially by the lateral pterygoid muscle, posteriorly by the condylar process of the mandible, anteriorly by the maxillary tuberosity, and superiorly by the Inferior surface of the greater wing of the sphenoid bone.

Inferiorly, the temporopterygoid space is continuous with the adipose tissue of the interpterygoid space (Fig. 57).

The temporopterygoid space contains: the deep temporal and masseteric nerves (deep temporal nerves and masseteric nerve), the buccal nerve, branches of the mandibular nerve, the lower parts of the pterygoid venous plexus, the maxillary artery, and its branches.

The pterygoid plexus surrounds the pterygoid muscles. It receives tributaries from: the parotid veins (from the parotid gland); the deep temporal veins (from the temporalis muscle); veins accompanying the sphenopalatine artery (from the nasal mucosa); veins from the pterygoid muscles; veins from the masseter muscle; veins accompanying the inferior alveolar artery; and middle meningeal veins, which drain blood from the dura mater and diploë.

Blood is drained from the pterygoid plexus via the maxillary vein into the retromandibular vein, and from there into the internal jugular vein.

The adipose tissue of the temporopterygoid space houses the largest branch of the external carotid artery—the maxillary artery—which supplies the deep facial region. It originates near the neck of the mandible, curving around it from the medial side. It passes between the temporalis and lateral pterygoid muscles, reaching the pterygopalatine fossa.

The fascial spaces of the temporopterygoid region communicate with the buccal fat pad, the pterygopalatine fossa via the pterygomaxillary fissure, the orbital cavity via the inferior orbital fissure, and the cranial cavity and cavernous sinus via the foramen ovale and foramen spinosum. Along the course of the maxillary artery, it communicates with the parotid bed; along the course of the masseteric artery and vein, with the submasseteric space; and via the pharyngeal process of the parotid gland, with the anterior compartment of the parapharyngeal space.

Inferiorly, the tissue of the temporopterygoid space continues into the interpterygoid space. The interpterygoid space (spatium interpterygoideum) is located between the pterygoid muscles.

It is bounded:

✵ laterally: by the mandibular ramus and the medial surface of the lateral pterygoid muscle;

✵ medially: by the lateral surface of the medial pterygoid muscle;

✵ superiorly: by the skull base;

✵ posteriorly: by the parotid gland;

✵ anteriorly: by the maxillary tuberosity and the buccal fat pad;

✵ inferiorly: by the medial pterygoid muscle.

The interpterygoid space contains: the mandibular nerve, the maxillary artery, and the pterygoid plexus.

In the medial part of the deep facial region lies the pterygopalatine fossa, which contains adipose tissue housing the maxillary artery, the maxillary nerve, and the pterygopalatine ganglion.

In inflammation of the maxillary sinus (maxillary sinusitis), ganglionitis of the pterygopalatine ganglion may develop, clinically manifesting as Sluder's neuralgia: burning pain accompanied by autonomic symptoms (lacrimation, sialorrhea, rhinorrhea, eyelid edema and erythema, and facial swelling).

Medial to the deep facial region, on the lateral wall of the Pharynx, lies the parapharyngeal space.

It is divided into two parts: anterior and posterior.

The anterior compartment is bounded by:

✵ medially — mm. levator et tensor veli palatini, m. constrictor pharyngis superior, fascia pharyngobasilaris, and the palatine tonsil;

✵ laterally — m. pterygoideus medialis and the pharyngeal process of the parotid gland;

✵ posteriorly — the muscles of Riolan's anatomical bouquet (m. styloglossus, m. stylopharyngeus, m. stylohyoideus) and the aponeurosis covering m. stylopharyngeus (aponeurosis stylopharyngeus);

✵ anteriorly — the lateral and medial walls merging into each other;

✵ superiorly — the skull base;

✵ inferiorly — the capsule of the submandibular salivary gland, which transitions into the connective tissue of the floor of the oral cavity.

The connective tissue of the anterior parapharyngeal space contains the ascending palatine artery (a. palatina ascendens), a branch of the facial artery that supplies the soft palate; pharyngeal veins (vv. pharyngeae et pl. pharyngeus); and the external palatine vein (v. palatina externa), which drains blood from the tonsil. It anastomoses with the pharyngeal veins and drains into the facial vein. The anterior parapharyngeal space communicates with: the bed of the parotid salivary gland, and through it, along the course of the artery, with the interpterygoid space; the connective tissue of the floor of the oral cavity, and through it with the bed of the submandibular salivary gland; along the course of n. tensor veli palatini — with the interpterygoid space; and along the course of pl. pharyngeus — with the posterior parapharyngeal space.

The posterior parapharyngeal space is located between the lateral wall of the pharynx and the parotid salivary gland.

It is bounded by:

✵ medially — aponeurosis pharyngoprevertebralis, the septum of Charpy, which separates the posterior parapharyngeal space from the retropharyngeal space;

✵ laterally — the styloid process, m. digastricus (posterior belly), m. sternocleidomastoideus;

✵ posteriorly — the prevertebral fascia;

✵ anteriorly — the styloid process and its originating muscles (m. stylopharyngeus, m. styloglossus, m. stylohyoideus), and the stylopharyngeal fascia (aponeurosis stylopharyngeus or Jurasz's Diaphragm), which separates the anterior and posterior parapharyngeal spaces;

✵ superiorly — the skull base with the carotid canal (canalis caroticus) and jugular foramen (foramen jugulare) located here;

✵ inferiorly — continuing along the vessels and nerves into the carotid sheath (spatium vasonervorum) of the neck.

The posterior parapharyngeal space contains: the internal carotid artery (a. carotis interna); posterior and lateral to it — the internal jugular vein (v. jugularis interna); and between them — the Glossopharyngeal nerve (IX), vagus nerve (X), Accessory nerve (XI), and hypoglossus nerve (XII).

Posterior and medial to the artery, beneath the prevertebral fascia, lies the superior cervical sympathetic ganglion.

The internal jugular vein is surrounded by deep cervical lymph nodes.

The posterior parapharyngeal space communicates with: the superior Mediastinum — along the course of the vessels; the posterior mediastinum — along the course of the vagus nerve; the carotid sheath (spatium vasonervorum) of the neck — along the course of the vessels and the vagus nerve; the bed of the parotid salivary gland — along the course of the external carotid artery; the posterior cranial fossa — along the course of the internal jugular vein; the middle cranial fossa — along the course of the internal carotid artery; the cavernous sinus — along the course of the internal carotid artery; the bed of the submandibular salivary gland — along the course of the facial artery; and the connective tissue of the upper posterior neck region — along the course of the occipital vessels (a. et v. occipitales). Inflammatory processes (such as a furuncle or carbuncle of the neck) can develop in this connective tissue, with the spread of pus into the posterior parapharyngeal space. Inflammation of the connective tissue in the posterior compartment of the parapharyngeal space causes Villaret's syndrome — a combination of Horner's syndrome (myosis, enophthalmos, narrowing of the palpebral fissure) with unilateral paralysis of the Muscles of the soft palate, pharynx, Larynx, and vocal cord, alongside paresis or paralysis of the sternocleidomastoid and trapezius muscles. This symptom complex occurs when the IX, X, XI, and XII cranial nerve pairs and the cervical Sympathetic trunk are damaged.

The retropharyngeal space is a cleft filled with loose connective tissue, located posterior to the pharynx, between the buccopharyngeal fascia (fascia buccopharyngea, covering the posterior wall of the pharynx) and the prevertebral fascia. It contains: retropharyngeal lymph nodes, the inflammation of which leads to the formation of retropharyngeal abscesses, branches of the ascending pharyngeal artery (a. pharyngea ascendens), and the pharyngeal venous plexus (plexus venosus pharyngeus).

The space is bounded by: superiorly — the skull base; inferiorly — at the level of the sixth cervical vertebra, it transitions into the retrovisceral (extraorgan) space of the neck; laterally — aponeurosis pharyngoprevertebralis (Charpy's septum); anteriorly — the pharynx and the buccopharyngeal fascia covering it; and posteriorly — the prevertebral fascia.

The primary sign of inflammation in the connective tissue of the deep facial region is tonic contraction of the masticatory muscles (trismus), because the medial pterygoid muscle becomes involved in the purulent-inflammatory process. Subsequently, the inflammation spreads to all fascial spaces and, via the foramen rotundum, foramen ovale, and foramen spinosum, reaches the dura mater, while passing through the inferior orbital fissure into the orbital cavity.

A purulent inflammatory process on the face, such as a furuncle or carbuncle of the upper lip or the corner of the mouth, complicated by facial vein thrombophlebitis, inevitably spreads to the orbital veins, cavernous sinus, and pterygoid venous plexus, from where it reaches the dural venous sinuses via anastomoses, leading to sinus thrombosis followed by meningitis.

Inflammatory processes in the facial region are exceptionally severe and can sometimes result in the patient's death.

This is facilitated by:

1 The close proximity of vital anatomical structures.

2 The presence of venous plexuses and valveless veins. Consequently, septic emboli rapidly spread into the dural venous sinuses, leading to intracranial complications. The most hazardous in this regard are inflammatory foci in the upper lip area. Between the two nasolabial folds and the upper lip lies the "triangle of death," and soft tissue manipulations within this zone require extreme caution.

3 The presence of interconnected fascial spaces in the lateral facial region, which promotes the spread of inflammation to adjacent areas of the body (the orbit, parapharyngeal space, and mediastinum).