Orbit, Cavernous Sinus, and Eye Flashcards by Sarah Gillen

7 bones that make up the orbit

Sphenoid
Frontal
Ethmoid
Maxillary
Lacrimal
Zygomatic 
Palatine

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The thinnest portion of the orbit is the medial portion. What bones make up this portion?

Ethmoid
Lacrimal
Maxilla
Sphenoid

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3 foramina associated with the orbit

Supraorbital foramen
Superior orbital fissure
Optic canal

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What passes through the supraorbital foramen?

Supraorbital n.

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What passes through the superior orbital fissure?

Oculomotor n. (III)
Trochlear n. (IV)
Opthalmic division of trigeminal (V1)
Abducens n. (VI)
Ophthalmic vv.

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What passes through the optic canal?

Optic n. (II)

Ophthalmic a.

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What is the major muscle that assists in closing the eye?

What are its parts?

Orbicularis oculi m.

Orbital part
Palpebral part

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Innervation of orbicularis oculi m.

Temporal branches of CN VII

Zygomatic branches of CN VII

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Compare the actions of palpebral vs. orbital part of orbicularis oculi m.

Palpebral part closes the lid

Orbital part increases lid contact to eye and dilates the lacrimal sac

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What muscle acts as a direct antagonist to the orbicularis oculi by exposing the eyeball?

Levator palpebrae superioris (LPS)

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What muscle (under autonomic control) works with LPS to lift the eyelid and open the eye?

Superior tarsal muscle

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Innervation of LPS

CN III

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Innervation of superior tarsal muscle

Postganglionic sympathetic fibers originating from level of T1

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____ glands are modified sweat/sebaceous glands that form a sty when they become infected

Ciliary glands (Mebomian glands)

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Tears are formed by the _____ _____ at the superolateral aspect of the orbit. They are drained by ______ ______ located on the medial aspect of the orbit and eventually enter the _____ _____, travel via the ____ ____ to the inferior concha

Lacrimal gland; lacrimal canaliculi; lacrimal sac; nasolacrimal duct

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Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.

Parasympathetic innervation begins at the ____________ nucleus, then travels to the _________ ganglion

Superior salivatory nucleus; sphenopalatine

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Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.

Where does the parasympathetic synapse occur?

Sphenopalatine ganglion

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Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.

Sympathetic innervation begins at the ____________ ganglion

Superior cervical ganglion (carotid plexus)

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Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.

Where does the sympathetic synapse occur?

In the superior cervical ganglion (carotid plexus)

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Parasympathetic innervation to the lacrimal gland begins at the superior salivatory nucleus, then travels via what 3 nerves to get to the sphenopalatine ganglion where it synapses?

Facial n. (CN VII)
Greater superior petrosal n.
Vidian n.

[facial n. and greater superior petrosal n. join up with vidian n. to enter sphenopalatine ganglion where synapse occurs]

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For innervation of the lacrimal gland, once parasympathetics synapse in sphenopalatine ganglion, the ______ n. carries parasympathetics to the lacrimal gland where it becomes the _______ n. which provides true innervation to lacrimal gland

Zygomatic n. (CN V2); lacrimal n. (CN V1)

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What nerve carries sympathetics from superior cervical ganglion (carotid plexus) to the vidian nerve where it joins with parasympathetics?

Deep petrosal n.

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What 3 branches of CN V1 are visible on superior orbit dissection? — list from medial to lateral

Nasociliary
Frontal
Lacrimal

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3 branches of CN V1 seen on superior orbit dissection are nasociliary n., frontal n., and lacrimal n.

What are the 2 primary branches of the frontal n.?

Supraorbital n.

Supratrochlear n.

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Fractures of the bony orbit most commonly d/t high velocity trauma

Blow-out fracture

Clinical signs of blow-out fracture of orbit

Periorbital ecchymosis, edema, point tenderness, diplopia, decreased visual acuity, decreased pupillary reflex

Diplopia (usually of upward gaze) is most commonly due to entrapment of what muscle?

Inferior rectus m.

With a blowout fracture of the orbit, displacement of structures into what sinus is common?

Maxilary

Le forte fractures

Fractures of maxillary region of the skull

3 types of Le forte fractures

Type 1: above alveolar processes. Avoids the orbit (presents with lower lip swelling/ecchymosis, damaged teeth) Type 2: pyramidal shaped fracture. Involves medial orbit (presents with periorbital edema, CSF rhinorrhea, nasal disfigurement) Type 3: craniofacial dysjunction; transverse fracture across both orbits and nasofrontal sutures. Leads to separation from base of skull (presents with panda facies, complete mobility of facial skeleton, antimongoloid slant)

Cavernous sinuses are paired dural venous sinuses found between the ______ and ______ layers of dura mater. They are parasagittal to the hypophysis. What 3 structures boundary the cavernous sinuses?

Endosteal; meningeal Bounded by brain, sphenoid bone, and temporal (petrous) bone

What structures are just inferior to the cavernous sinus?

Sphenoidal sinuses

Contents of cavernous sinus

Mnemonic: OTOM CAt Oculomotor n. Trochlear n. Ophthalmic n. Maxillary n. internal Carotid a. Abducens n.

The cavernous sinus is a paired dural venous sinus, draining blood predominantly from the _____ veins, eventually delivering blood to the ______ sinuses and evenutally the _______

Ophthalmic; petrosal; IJV

Condition characterized by enlargement of cavernous sinus due to venous congestion secondary to hematological obstruction

Cavernous sinus thrombosis (CST)

Venous anastomosis of the cavernous sinus with the _____, _____, and ______ leads to potential obstruction in smaller compartments (like the petrosal sinus)

Sphenoid sinus; ophthalmic vv; facial v.

Clinical signs of cavernous sinus thrombosis

Acute onset of unilateral periorbital edema and proptosis, headache, photophobia, impingement syndrome (most commonly affecting CN VI)

Conjunctiva of the eye is divided into what 2 types?

Bulbar conjunctiva Palpebral conjunctiva [bulbar is what gets infected in pink eye; palpebral is examined in relation to potential anemia]

Eye structure that serves as exit point for retinal neuronal axons to form optic n.

Optic disc

Area of eye with high resolution and color distinction vision

Macula lutea

_____ =swelling of the optic disc due to increases in CSF

Papilledema

Input and output for corneal reflex

Input (sensation) in cornea = nasociliary n./long ciliary nn. (branches of CN V1) Output (motor) via facial n. to orbicularis oculi (CN VII) which causes direct and bilateral blinking

What is corneal reflex used to test for?

Assessment of neurological function; reflex will not occur in braindead individuals

Compare actions and type of response of the 2 muscles in the iris that control pupil diameter: sphincter pupillae vs. dilator pupillae

Sphincter constricts pupils (miosis) — parasympathetic response Dilator dilates pupils (midriasis) — sympathetic response

T/F: pupillary constriction reflex is a sympathetic response

False; it is parasympathetic

The pupillary constriction reflex begins when direct light stimulus travels via retina, stimulating the optic n. The reflex then travels to the ______ in the brainstem, through the ________ to the ________ nucleus. From there, it travels via the oculomotor n. to the _____ ganglion, then via _______ nn. to cause ipsilateral pupillary constriction

Superior colliculus; pretectum; edinger-westphal Ciliary; short ciliary

The pupillary constriction reflex causes direct and consensual (bilateral) responses. For the ipsilateral side, it begins when direct light stimulus travels via retina, stimulating the optic n. The reflex then travels to the superior colliculus in the brainstem, through the pretectum to the edinger-westphal nucleus. From there, it travels via the oculomotor n. to the ciliary ganglion, then via short ciliary nn. to cause ipsilateral pupillary constriction At one point does the signal cross to the contralateral side, and what pathway does it take?

Once the ipsilateral signal reaches the pretectum, it travels to the contralateral side via the posterior commissure. From there the pathway is the same — to the edinger westphal nucleus to the ciliary ganglion via oculomotor n. then causes contralateral pupillary constriction via short ciliary nn

Pupillary dilation reflex pathway

Direct light stimulus to left retina —> signal travels to superior colliculus in brainstem via optic n. —> pretectum —> reticular formation —> lateral reticulospinal tract —> preganglionic sympathetic neurons in spinal cord —> superior cervical ganglion —> dilator pupillae m. via long ciliary nn. —> bilateral pupillary dilation (mydriasis)

What muscle is responsible for controlling lens function to properly focus light?

Ciliary m.

Describe the condition of ciliary m. and zonular fibers under sympathetic conditions

Zonular fibers are taut and ciliary m. is relaxed [this is how these structures normally exist!] good for distant vision

What happens to ciliary muscle and zonular fibers under parasympathetic conditions?

Ciliary muscle constricts, relaxing the zonular fibers Good for near vision

Accommodation of the eye allows you to focus on structures/objects that are close. This is a ______-mediated reflex; outputs are sent out by the ________ to perform its functions

Cortically; occipital lobe

Outputs for accommodation reflex are sent out by the occipital lobe to perform what 3 simultaneous functions?

1. Convergence (pupils adduct) 2. Pupillary constriction 3. Lens thickening (near sightedness)

What is the chief artery of the orbit and what does it normally branch from?

Ophthalmic a.; branches from internal carotid a.

5 important branches of the ophthalmic a.

Posterior ciliary a. Central retina a. Supraorbital a. Supratrochlear a. Anterior ethmoidal a.

What do the posterior ciliary and central aa. of the retina supply?

The optic n.

What a. supplies the retina?

Central retina a.

What does the supraorbital a. supply?

Upper and lateral portions of eyelid and scalp

What does supratrochlear a. supply?

Medial portion of eyelid and scalp

What does anterior ethmoidal a. supply?

Nasal cavity and external nose

6 extraocular mm (EOMs)

``` Medial rectus Lateral rectus Inferior rectus Superior rectus Superior oblique Inferior oblique ```

Innervation of EOMs

``` Lateral rectus = CN VI Superior oblique = CN IV Medial rectus = CN III Inferior rectus = CN III Superior rectus = CN III Inferior oblique = CN III ``` [remember SO4 LR6, the rest are 3]

Action of medial rectus m.

Moves eye medially (adducts eye)

Action of lateral rectus m.

Moves eye laterally (abducts eye)

Action of inferior rectus m.

Moves eye inferiorly (depresses eye) and medially (adducts eye) Aka down and in

Action of superior rectus m.

Moves eye superiorly (elevates) and medially (adducts eye) Aka up and in

Action of inferior oblique m.

Moves eye superiorly (elevates) and laterally (abducts) Aka up and out

Action of superior oblique m.

Moves eye inferiorly (depresses) and laterally (abducts) Aka down and out

When assessing the cardinal signs of gaze, what eye movement do you use to assess the superior oblique m.?

Down and in [superior oblique anatomically moves the eye down and out, but superior oblique is best clinically evaluated by adducting the eye to neutralize the effects of inferior rectus m.]

What muscle is tested by down and out eye movements for cardinal signs of gaze?

Inferior rectus

What muscle is tested by lateral movement of the eyes for cardinal signs of gaze?

Lateral rectus

What muscle is tested with up and out eye movement with cardinal signs of gaze?

Superior rectus

What muscle is tested with up and in eye movements for cardinal signs of gaze?

Inferior oblique m.

A down and out pupil would be caused by a lesion in what CN?

CN III

Signs of trochlear n. lesion

Extorted pupil Notable vertical diplopia Compensatory head tilt and tucking of chin [may also get compensatory torticollis]

What ocular n. lesion would lead to medially rotated pupil?

Abducens lesion

Ptosis

Drooping/falling of upper eyelid

What muscles contribute to the motion of the upper eyelid? Which one is stronger?

LPS (stronger bc somatic control by CN III) Superior tarsal m. (Sympathetic nervous system controlled, weaker)

Complete ptosis is caused by _____ n. palsy

Oculomotor

What pupil presentation accompanies complete ptosis?

Down and out (bc oculomotor n. affected) Also pupillary dilation because loss of pupillary constriction reflex

What brainstem nuclei are involved in complete ptosis?

Edinger-Westphal nucleus

While complete ptosis is typically d/t oculomotor n. palsy, what causes partial ptosis?

Dysfunction of superior tarsal m. | Usually because of obstruction/destruction of sympathetic ganglion arc

Triad of findings associated with Horner’s syndrome

Partial ptosis Anhydrosis Miosis (constricted pupil)