orbit/radiology Flashcards
roof of the orbit
orbital plate of the frontal bone
lateral wall of the orbit
zygomatic bone and greater wing of sphenoid
floor of the orbit
-orbital plate of the maxilla, which separates the orbital cavity from the maxillary sinus
medial wall of the orbit
- frontal process of the maxilla
- lacrimal bone
- orbital plate of the ethmoid, and the body of the sphenoid
where do eyelids meet eachother?
-medial and lateral angles
palpebral fissure
-opening between the eyelids and the entrance into the conjunctival sac
what covers the deep surface of the eyelid?
-mucous membrane called the conjuncitva
tarsal glands
- modified sebaceous glands that open into the margin of the eyelid behind the eyelashes
- secrete oily substance to prevent tear overflow
orbital septum
- fibrous sheet that supports the eyelids
- attached to periosteum at oribital margins
tarsal plates
- thicked orbital margins
- tarsal glands are embedded in them
parts of the lacrimal gland
- large orbital part
- small palpebral part
preganglionic parasympathetic innervation of lacrimal apparatus
- from lacrimal nucleus of facial nerve
- travel greater petrosal nerve and nerve of pterygoid canal to synapse in pterygopalatine ganglion
Postganglionic parasympathetic innvervation of lacrimal apparatus
- leave pterygopalatine ganglion and travel V2(maxillary of trigeminal)
- reach lacrimal gland by lacrimal nerve
sympathetic postganglionic innervation of lacrimal apparatus
- from internal carotid plexus(T1-L2)
- join deep petrosal nerve and nerve to pteryoid canal to travel with preganglionic para
lacus lacimalis
- tears circulate across cornea and accumualte here
- lake of tears
lacrimal duct path
- lacrimal punctum to lacrimal canaliculi
- to lacrimal sac
- to nasolacrimal duct
- to inferior meatus of the nose
what surrounds the optic nerve?
- meninges
- nerve pierces sclera and meninges fuse with the sclera
CSF and optic nerve
- held in subarachnoid space
- pressure within cranial cavity is transmitted to the back of the eye
opthalmic division of trigeminal nerve : branches
- frontal
- lacrimal
- nasociliary nerves
frontal nerve
-divides into supraorbital and supratrochlear to supply skin of forehead
lacrimal nerve
joined by branch of zygomaticotemporal nerve to go to lacrimal gland and lateral, upper eyelid
Oculomotor supplies which EOM?
-all but superior oblique and lateral rectus
Lateral rectus nerve supply
-CN VI(abducens)
Superior oblique nerve supply
-CNIV(trochlear)
opthalmic artery is a branch of…
-internal carotid artery
branches of opthalmic artery
- central artery of the retina
- muscular branches
- ciliary arteries
- lacrimal artery
- subraorbital and trochleat arteries
Central artery of the retina
-runs within the optic nerve and enters the eye at the center of the optic disc
superior ophthalmic vein
-communicates in front with facial vein
Inferior ophathalmic vein
-communicates through inferior orbital fissure with pterygoid venous plexus
where do ophthalmic veins drain?*****
cavernous sinus
ciliary ganglion receives preganglionic fibers from…
-oculomotor nerve via nerve to inferior oblique
ciliary ganglion sends postganglionic fibers to…
-back of the eye for sphincter pupillae and cilary muscle
dilation of the eye
- postganglionic sympathetic fiber
- levator palpebrae superioris or occipitofrontalis
constriction of eye
- postganglionic para fiber
- sphincter
- occipital orbis
25 year old male presents to the ER with head trauma. Diagnostic test of choice?
-CT brain WITHOUT contrast
Which imaging modality of the brain causes no radiation exposure to the patient?
MRI
55 year old female presents to the ER with unilateral weakness, onset 30 minutes ago. Initial diagnostic test of choice?
-CT brain WITHOUT contrast
Why would you want to do an initial CT without contrast?
- contrast shows up white, and so does blood. so you cant tel bleeding
- contrast can stay in the head for a while too so you cannot monitor bleed
when would you use CT WITH contrast?
- in assessment of abnormal enhancement patterns
- masses and vascular abnormality
what does MRI use as imaging?
-DWI
what is MRI good at looking at?
-acute ischemia
why would you not just start with an MRI?
-you have to eliminate the idea of a hemorrhage before you cant look into ischemia
who would you not want to do an MRI on?
- pacemaker
- metal residues/orjects
- claustrophobia
is MRI done with or without contrast?
both
what kind of contrast is used in CT?
-iodine based
what kind of contrast is used in MRI?
- Gd (Gadolinium)
- not iodine based
what are the options for assessment of cerebral vasculature?
- CTA
- MRA
- ultrasound
- digital angio
how would you get around someone having a contrast allergy?
harvard prep medication
where do aneurysms normally happen on circle of willis?
-anterior communicating artery
what is the advantage of MRA?
-you do not need contrast
what is the clearest image for cerebral vasculature?
CTA
how should blood flow? antegrade or retrograde?
antegrade
what would cause retrograde?
-subclavian steal syndrome
what gives you the highes radiation for cerebral vasaculature?
digital angio
what are your options for spinal column?
- CR
- CT
- MRI
what is the initial assessment of trauma to the neck/ spine?
CR
what is the best imaging option for spinal cord?
-MRI
what do you suspect if there is subdural hematoma and chronic hermatoma in a child?
-shaken baby syndrome and child abuse
