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Home , Lacrimal canaliculi, Nasolacrimal duct, Palpebral fissure, Superior tarsal muscle

Lab 4: and

Review ”The Basics” and ”The Details” for the following cranial in the Cranial PowerPoint Handout. • Oculomotor n. (CN III) • Trochlear n. (CN IV) • Ophthalmic division trigeminal (CN V1) • Maxillary division trigeminal (CN V2) • Abducens n. (CN VI) Slide Title Slide Number Slide Title Slide Number Osseous Orbit Slide 3 Optic Disc and Optic Nerve Slide 21 Osseous Orbit (Continued) Slide4 Central of Retina Slide 22 Osseous Orbit (Continued) Slide 5 Macula Lutea and Fovea Centralis Slide 23 Palpebrae Slide 6 Papilledema Slide 24 Palpebrae: Tarsi, Glands, and Muscles Slide 7 Extraocular Eye Muscles: Optical Axis versus Orbital Axis Slide 25 Palpebrae: Muscles Slide 8 Extraocular Eye Muscles: Axes of Movement Slide 26 Palpebrae: Slide 9 Slide 10 Extraocular Eye Muscles: Muscles that Move the Eyes Slide 27 Slide 11 Extraocular Eye Muscles: Complete Anatomy Slide 28 Lacrimal Apparatus (Continued) Slide 12 Extraocular Eye Muscles: Actions Slide 29 Innervation Slide 13 H Eye Exam Slide 30 The Eye: Major Layers Slide 14 Extraocular Eye Muscles: Muscles That Move Slide 31 Fibrous Tunic Slide 15 Extraocular & Cranial Nerve Mnemonics Slide 32 Uvea (Vascular Tunic): Choroid, Ciliary Body, Ciliary Slide 16 Processes, and Ciliary Muscles Cavernous Sinus & Associated Cranial Nerves Slide 33 Lens Accommodation Slide 17 Cavernous Sinus & Venous Blood Slide 34 Uvea (Vascular Tunic): Iris Slide 18 Cavernous Sinus & Venous Blood (Continued) Slide 35 Autonomic Innervation to Pupillae and Ciliary Muscles Slide 19 Cavernous Sinus & Thrombosis Slide 36 Review: (CN III): The Details Slide 20 Osseous Orbit

The following bones form the walls of the the bony orbit (Figure 3). • Frontal • Ethmoid • The lamina papyracea (orbital lamina) is a thin, delicate layer of ethmoidal bone separating the orbit from the ethmoid air cells (sinuses) • Lacrimal • • A thin layer of maxillary bone separates the floor of the orbit from the maxillary sinus. • Zygomatic • Sphenoid • Palatine

Review the structures that pass through the the following apertures to enter and exit the posterior bony orbit. • Optic canal: Optic n. (CN II) and Ophthalmic a. • Superior orbital fissure: Ophthalmic n. (CN V1), Oculomotor n. (CN III), Trochlear n. (CN IV), Abducens n. (CN VI), Sympathetic fibers, Ophthalmic veins • Inferior orbital fissure: Infraorbital n. branch of Maxillary Zygomatic Infraorbital n., Zygomatic branch of of Maxillary n., Infraorbital vessels nerve nerve Osseous Orbit (Continued)

Figure 5

Review the structures pass through the the following apertures to exit the anterior bony orbit. • Supraorbital notch/foramen: Supraorbital n. branch of Ophthalmic n. (CN V1) & Supraorbital Supraorbital vessels foramen/notch • Infraorbital foramen: Infraorbital n. branch of Maxillary n. (CNV2)

Infraorbital foramen Osseous Orbit (Continued) Figure 3 The medial (lamina papyracea) and inferior walls of the orbit are quite thin. These thin regions of the bony orbit separate the orbit from the ethmoid sinuses (air cells) medially and the maxillary sinuses inferiorly (Figure 1).

CLINICAL ANATOMY: Because the margins of the orbit are significantly stronger than its walls, trauma to the orbit may result in either a separation and displacement of bones at sutures, or a fracture of one or more of its walls (“blowout” fracture) (Figures 2, 3, and 4). Fractures of the medial wall may involve the ethmoid or sphenoid sinuses; fractures of the inferior wall may affect the maxillary sinus and infraorbital nerve. • Diplopia and heterotropia (abnormal eye alignment) can result from from a muscle becoming entrapped at the fracture site or from swelling that alters the function of an eye muscle. The muscle most often affected in a blowout fracture is the because of its position along the thin, inferior floor of the orbit.

Figure 1 Figure 2 Figure 4 Palpebrae

• The palpebra (Pl. = palpebrae) is the anatomical term for eyelid. • The opening between the superior and inferior eyelids is the . • Closing of the palpebral fissure is controlled by the facial nerve (CN VII) • Opening of the palpebral fissure is controlled by the oculomotor nerve (CN III) and sympathetic fibers.

Palpebrae

Palpebral Fissure Palpebrae: Tarsi, Glands, and Muscles

The tarsi (superior and inferior tarsal plates) are elongated plates of dense connective tissue forming the inner core of each eyelid. • The tarsal (meibomian) glands are embedded within each . The glands are a modified sebaceous gland that secretes a lipid substance onto free edge of the eyelid at the posterior border. The secreted lipid prevents evaporation and forms a barrier that prevents spilling of lacrimal fluid out of the eyelids. • Associated with the projecting from the anterior border of the eyelid's free edge are sebaceous glands called ciliary glands.

CLINICAL ANATOMY: Blockage and inflammation of a ciliary gland leads to the formation of a stye on the edge of the eyelid.

Muscles that open palpebral fissure • The levator palpebrae superioris muscle has a deep insertion on the tarsus and a superficial attachment to the the skin of the eyelid. This muscle elevates the upper eyelid and opens the palpebral fissure. It is innervated by the oculomotor n. (CN III). • The superior tarsal muscle is a short slip of that extends from the levator palpebrae superioris to the superior margin of the tarsus. This small slip of smooth muscle assists the levator palpebrae superioris in elevating the upper eyelid. This muscle is innervated by the sympathetic nervous system.

CLINICAL ANATOMY: Loss of function of the superior tarsal muscle (via loss of sympathetic innervation) results in a partial of the upper eyelid. In addition, loss of sympathetic innervation will result in a pin-point pupil due to a lack of innervation to the dilator pupillae muscle (parasympathetic innervation still intact). Partial ptosis can also the result of a partial third nerve palsy, but in this condition the pupil will be dilated. Palpebrae: Muscles

Muscles that close the palpebral fissure (Figure 1) • The consists of two parts, which are both innervated by the facial nerve (temporal and zygomatic branches). • The palpebral portion of the muscle gently closes the palpebral fissure, as in normal blinking. • The orbital portion of the muscle tightly closes the palpebral fissure.

CLINICAL ANATOMY: Injury to the facial nerve or its branches resulting in loss of tonus to the orbicularis oculi muscle causes superior eyelid retraction and the inferior eyelid to fall away from the surface of the eye (ectropion) (Figure 2). The inability to blink results in lacrimal fluid not being spread across the surface of the cornea. This can lead to inadequate lubrication, hydration and flushing of the corneal surface, which renders it vulnerable to ulceration. A corneal scar as a result of ulceration can permanently impair vision. Figure 1 Figure 2 Palpebrae: Orbital Septum

The orbital septum is a fibrous membrane that spans the distance between the tarsal plates and the bony margins of the orbit, where it is continuous with the periosteum of the bone.

CLINICAL ANATOMY: The orbital septum is clinically important because it can limit the spread of infection to and from the orbit. However, it can also confine an infection within the orbit. Conjunctiva The covering of the eyelid not in contact with the eye (external covering) differs from the covering of the eyelid that is in contact with the eye (internal covering). • The external eyelids are covered by thin skin, which consists of a thin stratum corneum relative to skin in other areas of the body. • The internal eyelid is covered by a transparent mucous membrane, called the palpebral conjunctiva (Figure 3A). The palpebral conjunctiva reflects onto the anterior surface of the eye (white and transparent cornea) to become the the bulbar conjunctiva at the superior and inferior conjunctival fornices. • The bulbar conjunctiva covering the sclera contains small blood vessels, which are visible when viewing someone's eye. However, the cornea itself is avascular. • When the eyelids are closed the palpebral and bulbar conjunctiva form the closed conjunctival sac. The conjunctival sac is a specialized form of mucosal “bursa” that enables the eyelids to move freely (frictionless) over the surface of the eye as they open and close.

CLINICAL ANATOMY: Inflammation of the conjunctiva, (conjunctivitis, or “pink eye” to patients), is quite common. It is caused by a variety of bacteria and viruses, allergic reactions, or by toxins or irritants (e.g. dust). In most cases, conjunctivitis is not dangerous. However, certain bacteria, especially N. gonorrhoeae and C. trachomatis, can cause severe damage or even blindness.

Conjunctival fornix Lacrimal Apparatus The lacrimal gland is located in the superolateral aspect of the orbit and is divided into a superior (orbital) part and a palpebral (inferior) part by the lateral tendon of the levator Tendon levator palpebrae superioris muscle. palpebrae superioris Lacrimal fluids secreted by the lacrimal gland are swept across the cornea and conjunctiva of the eye during blinking. At the medial angle (medial ) of the eye the lacrimal fluid is removed from the surface of the eye by passing through the following structures. • Fluid drains into the lacrimal puncta, which are small openings on the conical protrusion called the lacrimal papilla on the medial eyelid. Once the fluid passes through the punctum, it enters the .

• The canaliculi are short channels that drain the lacrimal fluid to the , which are dilated regions of the most superior part of the . The lacrimal sac drains via the nasolacrimal duct to the inferior nasal meatus within the . Lacrimal Apparatus (Continued)

• The lacrimal fossa is located in the inferomedial aspect of the orbit. In the living skull, the lacrimal sac resides within the lacrimal fossa. • The contains the nasolacrimal duct on its pathway to empty into the inferior nasal meatus within the nasal cavity.

Entrance Nasolacrimal Canal

https://3d4medic.al/I4A8AX3g Lacrimal Gland Innervation

Review the autonomic innervation to the lacrimal gland using the following resources. • Picture to the right • Cranial nerve PowerPoint Handout (Lab 2): Facial nerve (CN VII) • Cranial Nerve Table (Lab 2) • PRL of oculomotor nerve (CN VII) Autonomics • Lab 2: Facial Nerve (CN VII), Part 1, Pterygopalatine Ganglion (Panopto) • Lab 2: Facial Nerve (CN VII), Part 2 Lacrimal Gland (Panopto) The Eye: Major Layers

The eyeball consists of three major layers. • The fibrous tunic is the outermost layer of the eye consisting mostly of collagenous connective tissue. • The vascular tunic, which is often called the uvea in a clinical setting, is the middle layer of the eye. As its name implies, it is a well vascularized region. • The retina (nervous tunic) is the innermost layer of the eye consisting of three layers of neurons. The layer of neurons closest to the uvea contains specialized neuronal cells called photoreceptors that are sensitive to visible light.

https://3d4medic.al/OQaj93Ec Fibrous Tunic

The fibrous tunic is composed of two regions : sclera and cornea. • The sclera is the white of the eye and forms the posterior 5/6 of the outer layer of the eyeball. It consists of dense fibrous connective tissue forming a tough, nontransparent outer protective layer that maintains the shape of the eyeball.

• The cornea is the anterior continuation of the sclera that forms the anterior 1/6 of the outer layer of the eyeball. It is a transparent layer that refracts the majority of the light entering the eye, which means it is the primary structure that focuses light. Since it is through this layer that light must travel to enter the eye, it is considered the window of the eye.

CLINICAL ANATOMY: The corneal reflex is elicited by gently touching the upper part of the cornea with a wisp of cotton or tissue. (The lower cornea isn't ideal because in some individuals the lower cornea is innervated by the maxillary (CN V2) nerve.) In response to corneal light touch stimulation, both eyes should blink. The afferent portion of the reflex is transmitted by the ophthalmic nerve (CN V1) via its nasociliary branch. The efferent portion of the reflex is transmitted by the facial nerve (CN VII) via its zygomatic and/or temporal branches. Uvea (Vascular Tunic): Choroid, Ciliary Body, Ciliary Processes, and Ciliary Muscles

The uvea consists of the following layers: choroid, ciliary body, and iris. • The choroid forms the posterior 5/6 of the uvea and is sandwiched between the retina and the sclera. It is a well vascularized layer that also contains a lot melanin pigment, which is the reason the layer appears dark. Vessels within the choroid are NOT the vessels observed when performing a funduscopic examination of the eye.

• The ciliary body is the anterior continuation of the choroid and is a region of the uvea bulges inward toward the lens. The bulge of the ciliary body reflects that the ciliary body contains smooth muscle fibers that, as a whole, are called the .

• The ciliary processes are projections of the ciliary body covered by epithelial cells that produce aqueous humor. Zonular fibers (suspensory ligaments) are thin connective tissue fibers that connect the ciliary processes to the lens.

• Contraction of the ciliary muscles moves the ciliary body closer to the lens, which decreases tension being placed on the lens. Decreased tension on the lens allows the lens to bulge. As an object is moved closer to the eye, this process allows for the lens to increase refraction beyond the refraction accomplished by the cornea. (Next Slide). Lens Accommodation

FUNCTIONAL ANATOMY: Lens accommodation is the process by which the eye can alter its focal distance (increase refractive power) for a near object. This increase in refraction results from bulging of the lens. The accommodation reflex includes bulging of the lens, eye convergence, and pupil constriction. The process of pupillary constriction is not entirely clear, but probably functions to increase depth of field, which reduces the amount of accommodation needed to focus an image on the retina. Uvea (Vascular Tunic): Iris

The iris is a thin circular structure that is the most anterior structure of the uvea. It contains varying amounts of the pigment melanin, which causes the iris to vary in color from person to person. The pupil is the hole in the middle of the iris that is variable in size and allows light to enter the eye and ultimately fall on the retina. Two intrinsic eye muscles within the iris function to change the size of the pupil. The two muscles located within the iris are the constrictor pupillae and dilator pupillae muscles. • The constrictor pupillae consists of smooth muscle cells arranged in a circle around the pupil, and when it contracts, the size of the pupil decreases. It is innervated by parasympathetic neurons originating from the oculomotor nerve.

• The dilator pupillae consists of radially oriented myoepithelial cells. When the myoepithelial cells contract, the pupil increases in size. It is innervated by the sympathetic nervous system. Autonomic Innervation to Pupillae and Ciliary Muscles

Review the autonomic innervation to the pupillae muscles and ciliary muscle using the following resources. • Picture to the right • Cranial Nerve PowerPoint Handout: Oculomotor nerve (CN III): Next slide copied and pasted from the Cranial Nerve PowerPoint handout. • Cranial Nerve Table (Lab 2) • PRL of oculomotor nerve (CN III) Autonomics: Lab 2: CN III Autonomics (Panopto) Review: Oculomotor Nerve (CN III): The Details

Pathway: CN III emerges from the midbrain and pierces the dura mater lateral to the sellar diaphragm. It then courses through the lateral wall of the cavernous sinus to enter the orbit through the superior orbital fissure.

• GSE fibers of the oculomotor nerve innervate levator palpebrae superioris and extraocular eye muscles (superior rectus, inferior rectus, medial rectus, and inferior oblique muscles).

• GVE fibers of the oculomotor nerve enter the ciliary ganglia. Within the ganglion, preganglionic fibers synapse with postganglionic fibers. Postganglionic fibers leave the ganglion and enter the eye via short ciliary nerves. Within the eye the postganglionic fibers innervate the sphincter pupillae (pupillary constriction) and the ciliary muscles (accommodation of the lens for near vision). Optic Disc and Optic Nerve The retina consists of a complex layering of neuronal cell bodies and regions of neuronal synapses. (Details of the retina will be studied at a later time during MBB.) • The layer of neurons closest to the uvea contains specialized neuronal cells called photoreceptors that are sensitive to visible light (rods and cones) (Figure 1). • The optic disc is the region of the retina where axons of ganglion cell neurons coalesce to exit the eye and form the optic nerve. The optic disc region does not contain photoreceptors, so light striking this region of the retina cannot be perceived. Since light can’t be “seen” when it strikes this area of the retina, this region is also known as the blind spot (Figures 2 and 3). FUNCTIONAL ANATOMY: The blind spot is typically not perceived because of several reasons. • Since it is located in different fields of view for each eye, when light is falling on the blind spot of one eye, the other eye compensates. • The brain ”fills in” missing information from our field of vision as to what it presumes is present. • The eye is constantly moving, so light from a particular object is only striking the blind spot for a short time.

Figure 1 Figure 2 Figure 3 Optic Disc (Blind Spot) Optic Nerve

Layer of Rods & Cones Vitreous Chamber

Choroid Central Artery of Retina Figure 2 The retina contains an extensive network of branching blood vessels derived mainly from the central artery of the retina that enters the retina at the optic disc (Figure 1). • The central artery of the retina is the only blood supply to the inner region of the retina. • The branches of the central artery are easily viewed during a funduscopic examination of eye.

The clear space internal to the retina is called the vitreous chamber. It is filled with vitreous humor, which is a jelly-like transparent mass that assists with maintaining the shape of the eyeball (Figure 2). Figure 1

Vitreous Chamber Macula Lutea and Fovea Centralis

The macula lutea is an oval area located in the center of the retina directly in line with the pupil (Figure 1). • This region contains a high concentration of cone cells, so it is a critical area for visual acuity. Even though the area is often described as a yellow oval, in ophthalmoscope examination it will never appear yellow, but instead look like a darkened circle. • The fovea centralis of the macula lutea is the central region of the macula that in histological section is visible as a depression in the retina. The fovea is the area of the macula that contains the highest concentration of cones and is involved in detecting the sharpest vision (Figure 2).

Figure 1 Figure 2 Vitreous Chamber

Fovea Centralis

Retina Layer Rods and Cones

Choroid

Sclera Papilledema

CIINICAL ANATOMY: Papilledema refers to optic disc swelling the occurs when elevated intracranial pressure is transmitted to the optic nerve sheath. This elevated pressure interrupts axoplasmic flow within the axons of the nerve causing water, protein, and other cellular contents to leak into the extracellular space of the optic disc, which leads to optic disc edema. The edema within the optic disc region can typically be visualized upon ophthalmic examination of the retina. Extraocular Eye Muscles: Optical Axis versus Orbital Axis The eye is located in the anterior aspect of the orbit. The equator of the eye, which is defined by a coronal plane passing through its middle, corresponds with the lateral orbital margin (black dashed line: Figures 1 and 2).

Relative to one another, the medial walls of the orbits are parallel, while the lateral walls are at a right angle to each other. The orbital axis and the optical axis are not parallel (differ by 23°) • The orbital axis divides the orbit in half (blue dashed line: Figure 1) • The visual (optical) axes extend from the anterior pole of the eye (center of cornea) to the posterior pole (fovea centralis). The visual axes are aligned in the sagittal plane.

CNS pathways, including “hard wiring” between and among the nuclei of cranial nerves III, IV and VI ensure that the visual axis can always be aimed at whatever someone wants to see most clearly. Figure 1 Figure 2

Lateral Margin Orbit Extraocular Eye Muscles: Axes of Movement

Movements of the eye are defined on three axes of rotation which intersect in the middle of the eye: • Movements on the vertical axis (Y axis) = abduction and adduction (of the anterior pole) • Movements on the transverse axis (X axis) = elevation and depression (of the anterior pole) • Movements on the sagittal axis (Z axis) (defined by movement of the superior surface of the eye) = intorsion (medial rotation) and extorsion (lateral rotation)

Important Concept: If a muscle is oriented at 90o to an axis, all of its force is applied to movement on that axis. If a muscle is oriented at 0o to an axis (in the same plane), none of its force can be applied to movement on that axis. As the angle between a muscle and an axis changes, the amount of force the muscle applies to movement on that axis changes correspondingly. Extraocular Eye Muscles: Muscles that Move the Eyes work together to move the eyes. • Rectus muscles: • All four rectus muscles originate from a common tendinous ring at the apex of the orbit. • Rectus muscles insert anterior to equator of eye, and are aligned with the orbital axis (not the visual axis) (Figure 1). • Four rectus muscles: Figure 2 • Two horizontal rectus muscles: medial and lateral rectus • Two vertical rectus muscles: superior rectus and inferior rectus • Oblique muscles: • Oblique muscles attach posterior to the equator of the eye. • The is oriented medial/superior in the orbit. Its tendon hooks through the trochlea (L. pulley), which is a loop of connective tissue just posterior to the orbital margin between the roof and medial wall. The tendon courses obliquely back over the superior surface of sclera, and inserts laterally and posterior to the equator. • Inferior oblique: this muscle originates from the anterior/medial aspect of floor of orbit and inserts laterally and posterior to the equator, in the same plane as the tendon of superior oblique. Figure 1 Extraocular Eye Muscles: Complete Anatomy

https://3d4medic.al/I14cGBci https://3d4medic.al/U6o6cPOg Extraocular Eye Muscles: Actions Moyer PRL of Extraocular Eye Muscle Actions: Lab 4: Extraocular Muscle Actions (Panopto) Muscle Primary Action Secondary Action Tertiary Action Cranial Nerve ”H” Eye Exam (Next Slide)

Medial Rectus Adduction ------Oculomotor Adduction

Lateral Rectus Abduction ------Abducens Abduction

Superior Rectus Elevation Intorsion Adduction Oculomotor Abduction/Elevation

Inferior Rectus Depression Extorsion Adduction Oculomotor Abduction/Depression

Superior Oblique Intorsion Depression Abduction Trochlear Adduction/Depression Inferior Oblique Extorsion Elevation Abduction Oculomotor Adduction/Elevation

Keep in mind that in the real world, the extrinsic muscles do not act in isolation; they all have some tone most of the time. Also, the muscles obviously exert all of their actions whenever they contract. However, most students find it useful to start by understanding the individual actions of each muscle as if they could occur in isolation. Abduction/Adduction Elevation/Depression

Intorsion/Extorsion H Eye Exam Moyer PRL of “H” Eye Exam: Lab 4: H Eye Exam (Panopto) When the eye is in a neutral position, the medial and lateral recuts muscles are easily tested. • Medial rectus = abduction • Lateral rectus = adduction

When the eye is in a neutral position, elevation and depression occur by the actions of more than one muscle, so testing from this position isn’t useful. • Elevation: superior rectus & inferior oblique • Depression: inferior rectus & superior oblique To test the muscles listed above, the action of each muscle must be isolated. This isolation can be achieved by ABDUCTING and ADDUCTING the eye. Lateral: When the eye is fully abducted, the axis of the superior and inferior rectus muscles is Medial: When the eye is fully adducted, the axis parallel to the axis of the eye. In this position, of the oblique muscles is parallel to the axis of only the superior and inferior rectus muscles act the eye. In this position, only the oblique to elevate/depress the eye. muscles act to elevate/depress the eye. • Superior rectus = abduction + elevation • Lateral rectus = abduction Medial rectus = adduction Inferior oblique = adduction + elevation • Inferior rectus = abduction + depression • Superior oblique = adduction + depression

Axis of Axis of = superior and superior and inferior rectus = inferior obliques Axis of = eyeball Axis of = eyeball Extraocular Eye Muscles: Muscles That Move Eyelids The extraocular muscles work together to move the upper eyelids and the eyes. • Muscles that move the eyelids • Levator palpebrae superioris: this muscle arises from the apex of the orbit and inserts along the skin of the eyelid where it interdigitates with the (palpebral) fibers of the orbicularis oculi; the levator palpebrae superioris is innervated by CN III. • Superior tarsal muscle: this bundle of smooth muscle extends from the distal tendon of the levator palpebrae superioris to the superior edge of the superior tarsal plate. It is innervated by sympathetic motor neurons. Extraocular & Eyelid Cranial Nerve Mnemonics

SO4 LR6 AR3

Superior Oblique Muscle = Trochlear n. (CN IV)

Lateral Rectus Muscle = Abducens n. (CN VI) All the Rest = Oculomotor n. (CN III)

CN VII: “7” is like a hook that pulls down on the eyelid. III CN III: Roman numeral III is like 3 pillars that holds up the eyelid. 7 (Also, don’t forget about the superior tarsal muscle innervated by sympathetic fibers) Cavernous Sinus & Associated Cranial Nerves

Recall that the cavernous sinus is a large venous plexus located on either side of the sella turcica. It extends from the superior orbital fissure anteriorly to the apex of the petrous part of the temporal bone posteriorly.

All structures that pass into the orbit through the superior orbital fissure are located within either the lateral wall of the cavernous sinus or pass directly through it. The maxillary nerve on its course to the foramen rotundum is also located in the lateral wall of the cavernous sinus. In addition, the internal carotid artery courses through the cavernous sinus.

Structures in the lateral wall of the cavernous sinus • Oculomotor nerve • Trochlear nerve • Ophthalmic division trigeminal n. (CN V1) • Maxillary division trigeminal n. (CN V2)

Structures passing through the cavernous sinus • Abducens nerve • Internal carotid artery Cavernous Sinus & Venous Blood

• Recall that blood in the cavernous sinus has the following drainage pathways. • Posterolaterally into the junction of the transverse and sigmoid sinuses via the the superior petrosal sinuses. • Posteroinferiorly • Into the junction of the sigmoid sinuses and internal jugular vein via the inferior petrosal sinuses • Into the the internal vertebral venous plexus via the basilar plexus • Inferiorly to the pterygoid venous plexus located in the deep face

Sella Turcica Cavernous Sinus & Venous Blood (Continued)

The facial vein communicates with the cavernous sinus by two major pathways. These vessels drain blood from the , orbit, and face. • Superior and inferior ophthalmic veins à cavernous sinus • Deep facial vein à pterygoid plexus à cavernous sinus

CLINICAL ANATOMY: Because the facial vein communicates with the cavernous sinus, infections introduced into the facial vein from lacerations of the nose or the squeezing of pustules (pimples) on the side of the nose and upper lip, may spread to the cranial dural sinuses. Facial v. This area of the face that can lead to infections within the cavernous (angular v.) sinus, is called the “danger triangle” of the face. Inferior Ophthalmic v.

“Danger Triangle” of the face. Cavernous Sinus & Thrombosis

CLINICAL ANATOMY: Cavernous sinus thrombosis (CST) is a rare, life-threatening disorder. • Cavernous sinus thrombosis is usually septic, but can also be aseptic. Septic cases can occur after central facial infections, especially within the danger triangle of the face. • Thrombophilia is a significant risk factor for aseptic cavernous sinus thrombosis. Women who are pregnant, post-partum, or receiving oral contraceptives/hormone replacement therapy may be at an increased risk.

Thrombophlebitis of the cavernous sinus manifests as obstructed venous drainage and neurologic signs resulting from involvement of cranial nerves III, IV, V, VI, and the sympathetic plexus around the internal carotid artery. • Periorbital edema • Proptosis (bulging of eye) • Chemosis (swelling of the conjunctiva) • Diplopia from compression of the sixth (abducens), third (oculomotor) and fourth (trochlear) cranial nerves. • Internal ophthalmoplegia (non-reactive pupil) results from damage to sympathetic fibers from the short ciliary nerves (resulting in miosis: constriction) and/or from loss of parasympathetic fibers from cranial nerve III (resulting in mydriasis: dilation) • Numbness or paresthesia around the eyes, nose, forehead and loss of corneal blink reflex resulting from damage to the the ophthalmic nerve (CN V1) • Facial pain, paresthesia, or numbness resulting from compression/damage to of the maxillary nerve (CN V2).