Lecture 3 - Orbit and Meninges

Question 1

What is difference between layers around spinal cord and brain?

Answer 1

Brain - has menangial and periosteal layer of dura mater - then the periosteal layer goes around external skull and does not travel down to spinal cord

Question 2

What form the dural partitions? and what are they called?

Answer 2

Falx cerebri (V1) , falx cerebelli tentorium cerebeli (V1), diaphragma sellae 
-made of menangial layer of dura mater

Question 3

What is the blood supply to the dura?

• what layer
• names of arteries
• where do they come from
• what happens if they get damaged

Answer 3

• Meningeal arteries (anterior, middle and posterior) run in the outer periosteal dura mater layer
• Middle meningeal artery is larger, and comes from the foramen spinosum and divides into ant and post branch
• anterior branch is behind the pterion

Question 4

Where are the dural venous sinuses

• what are they formed by?
• where do they all drain?

Answer 4

sigmoid
inferior sagital 
superior sagital
straight sinus
confluence of sinus
right transverse sinus 
great cerebral vien 
superior petrosal sinus
carvenous sinus 

• The carvenous sinus drains back to sigmoid sinus, and then drains to IJV and exits the skull
• opthalamic viens also drain back to carvernous sinus
• Formed in-between the two layers of dura mater
• they are found where the dural partitions are
• all drain to IJV

Question 5

Why is the carvenous sinus important

Answer 5

• Because internal carotid and VI nerve run here
• also nerevs 3, 5, 6, V1,2 run through the walls
• so if there is something that happens here than 5 nerves and main blood supply to brain will be damaged
• this sinus lies either side of the sella tucica (the turkish saddle)

Question 6

*** Why is peri-orbital cellulitis dangerous?

Answer 6

• Opthalamic viens drain back to the carvenous sinus
• peri-orital cellulitis is a bacterial infection around the orbit of the eye
• this infection can drain back to the carvenous sinus
• if bacteria gets in here, can form a clot
• and this can result in a carvenous sinus thrombus which is fatal
• Pateint can die within a few hours
• Need to be operated on (no time for Antibiotics to work)

Question 7

Cause Racoon eyes

Answer 7

e. g car accident
- nothing to do with eyes
- may have a fracture over his skull or base of his skull
- there is a potential space between the periosteal layer and skin down into the lower and upper eyelids
- blood coming out of the skull crosses this periosteal layer coming to this space and if damaged it can accumulate here

Question 8

Problem with infection to emissary vein? where is this?

Answer 8

• These veins run between the outside of the cranial cavity and drain into venous sinuses within the brain
• if you get damage/ dirt to the skull, and damage emisary vien, then can get backteria ect that can get into sinuses in the brain, or even carvenous sinus and this could cause cranial symptoms.

Question 9

Venous drainage of the skull

Answer 9

• emissary vein (goes from sinuses to outside cranial cavity)
• also have cerebral viens that drain the cerebellum of brain and drain to venous sinuses
• and then have diploic viens which drain from the skull

-all connected, can see how infections can spread around brain in the venous drainage systems.

Question 10

Arachnoid mater and pia mater

Answer 10

Arachnoid mater - made of trabeculae, avascular, does not go into groover or fissures (excpet longitudinal fissure)

Pia mater - thin mmebrane which invests the surface of the brain

Question 11

Extradural hemorrhage

Answer 11

• epidural hemorrhage
• almost always arterial origins
• this is from menangial arteries (normally middle menangial arteries) in the periosteal layer of dura mater
• almost always associated with a skull fracture e.g damage to pterion
• blood collects between skull and periosteal layer

-eg. car accidents

Question 12

subdural heamorrahage

Answer 12

• occurs within the menangial layer of dura
• usually due to venous structure
• e.g cerebral viens in the sub arachnoid space cross the arachnoid mater and get into the venous sinus - subdural viens
• usually in eldery - when brain shrinks then can damage these structures

Question 13

Subarachnoid haemorrhage

Answer 13

• in sub arachnoid space
• usually arterial origin (cerebral artery)
• usually from a ruptured cerebral artery aneurysm of circle of willis
• intracerebral bleed, causes sudden severe headache, vomiting, frequently loss of consciousness

Question 14

Ptosis

Answer 14

If eyelid is droping a bit more than the other - partial ptosis, and if shut eye - then complete ptosis

Question 15

Ptosis

-partial and complete - differences between them

Answer 15

If eyelid is dropping a bit more than the other - partial ptosis, and if shut eye - then complete ptosis

Partial - Superior tarsal muscle (smooth muscle), this is innovated by postganglionic sympathetic fibers from the superior cervical ganglion - in neck
-sometimes with excessive sweating (hyperhydrosis) surgeons will chop sympathetic chains - however can result in partial ptosis - horner syndrome

Complete - due to lwevator palpebrae superiors - innovated by occulomotor nerve

Question 16

Sty in eyelid

Answer 16

Tarsal gland - not draining the oily substances, gradually happens - has no pain

Sty in eyelid close to eye - due to the sweat glands getting infected - this one comes with pain

Question 17

Blood supply and innovation of eyelid

Answer 17

Blood supply - facial arteyr, superficial temproal artery

Sensory - first diviison of trigemenial - upper eyelid

lower - second division of trigeminal (maxilalyr)

Question 18

Obicularis oculi - what parts, what is it innovated by?

, orbital septum

Answer 18

Obicularis oculi - has orbital part and palperbal part - innovated by facial part
-damage - not able to close eye or blink upper eyelid , and lower eyelid wil droop

underneath is orbital septum - is an extension of periosteal layer of skull

-innovated by frontotemporal branch of facial nerve

Question 19

Conjunctivitis

Answer 19

membrane of conjunctiva has got infected

Question 20

Damage to tendionosu ring? why is this bad?

Answer 20

Alot of nerves here could be damaged

Question 21

Lacrimal apparatus

Answer 21

puncta, lacrimal canaliculi, lacrimal sac, nasolacrimal duct, lacrimal gland

lacrimal gland drains tears back to eye, into the duct and on medial side of the eye have a lake - all tears coming to this part

• pump - called puncta - drains tears back to lacrimal canaliucuili and back to sac
• always gett a runny nose when cry as tea s darin into nasolacrimal duct

dacryocytocele - duct is blocked in children, and baloon comes out of nose -

Question 22

Arteries of eye

Answer 22

ophthalmic artery, central retinal artery - will go blind if lose these
opthalamic vien - drains back to cavernous sinus - any infection may drain back here

Question 23

Innovations of eye muscles?

how to assess these

Answer 23

SO4
LR6
rest by 3

superior (levator palperbrae, superior rectus) and inferior branch of occulomotror (medial rectus, inferior rectus, inferior oblique)

• damage - ptosis
• not able to look up

Numeber 4- superior optic has 2 bellies, and doesnt origin from the tendinous arch, goes to medial side of eyeball - if there is damage to skull, then may loose the trochlea tendon - and so nerve doesnt work - nerve may not be damanged but attatchment

Exam - In clinical senarios - say things like the nerve may be damaged, or the attatchment may be damged - exam this to do with nerve, or get a CT to see if attatchment - need to know how you are goign to aply knowledge

Question 24

Ophthalmic nerve - V1

Answer 24

lacrimal nerve –> lacrimal gland
frontal nerve -> sensory to forehead (in exam e.g say damage here, then would say may loose nerve here due to damage)
nasocilary nerve –> to lacrimal duct

Question 25

Ophthalmic viens and their connection to the cavernous sinus

Answer 25

Many facial viens go into opthalamic vien then into cavernous sinus.

• Facial and opthalamic viens do not have valves, meaning infection in danger triangle can spread posteriorly to cause spetic cavernous sinus thrombosis
• Aim of researhc - determine if veiwns had valves or not, and role in periorbital abcess or cellulitis and carvenous sinus thrombosis
• Restuls - superior opthalamic, angular and supraorbital viens have valves. Cause of infection spreading intracranially is not due to valvless veins but due to the fact that blood from facial vien inferiorly adn supraobrital viens tracts back to carvenous sinsu via mulitple pathways.

-No correlation between absence of valves and increase risk of intracranial infection.

Question 26

Buising within the septum

Answer 26

• can see dark rings on eyelids when shut
• not racoon eyes (lower and upper eyelid filled with blood)
• damage to septum within eyelid causign rupture of small vessles due to trauma

N.B An increased ICP will affect the abducens nerve first (the eye is medially deviated and can not
move laterally from the midline), then the trochlear never (can not look down and in) and finally the optic nerve (oedema of the optic disc caused by impeded venous return along retinal veins.

Question 27

30 year old man - unable to shut eye, and whistle

Answer 27

Obicularis oculi - is damaged

Question 28

what muscle does not attatch at tendinous ring?

Answer 28

inferior oblique