Orbit, Cavernous Sinus, and Eye Flashcards
7 bones that make up the orbit
Sphenoid Frontal Ethmoid Maxillary Lacrimal Zygomatic Palatine
The thinnest portion of the orbit is the medial portion. What bones make up this portion?
Ethmoid
Lacrimal
Maxilla
Sphenoid
3 foramina associated with the orbit
Supraorbital foramen
Superior orbital fissure
Optic canal
What passes through the supraorbital foramen?
Supraorbital n.
What passes through the superior orbital fissure?
Oculomotor n. (III) Trochlear n. (IV) Opthalmic division of trigeminal (V1) Abducens n. (VI) Ophthalmic vv.
What passes through the optic canal?
Optic n. (II)
Ophthalmic a.
What is the major muscle that assists in closing the eye?
What are its parts?
Orbicularis oculi m.
Orbital part
Palpebral part
Innervation of orbicularis oculi m.
Temporal branches of CN VII
Zygomatic branches of CN VII
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
What muscle acts as a direct antagonist to the orbicularis oculi by exposing the eyeball?
Levator palpebrae superioris (LPS)
What muscle (under autonomic control) works with LPS to lift the eyelid and open the eye?
Superior tarsal muscle
Innervation of LPS
CN III
Innervation of superior tarsal muscle
Postganglionic sympathetic fibers originating from level of T1
____ glands are modified sweat/sebaceous glands that form a sty when they become infected
Ciliary glands (Mebomian glands)
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
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
Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.
Where does the parasympathetic synapse occur?
Sphenopalatine ganglion
Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.
Sympathetic innervation begins at the ____________ ganglion
Superior cervical ganglion (carotid plexus)
Innervation of lacrimal gland comes from both sympathetic and parasympathetic systems.
Where does the sympathetic synapse occur?
In the superior cervical ganglion (carotid plexus)
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]
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)
What nerve carries sympathetics from superior cervical ganglion (carotid plexus) to the vidian nerve where it joins with parasympathetics?
Deep petrosal n.
What 3 branches of CN V1 are visible on superior orbit dissection? — list from medial to lateral
Nasociliary
Frontal
Lacrimal
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.
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?
- Convergence (pupils adduct)
- Pupillary constriction
- 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)
