Eye and Raised Intracranial Pressure Flashcards Preview

Ophthalmology Anatomy > Eye and Raised Intracranial Pressure > Flashcards

Flashcards in Eye and Raised Intracranial Pressure Deck (46):
1

What are the two humours of the eye and where are they located?

Aqueous humour = Anterior to lens
Vitreous humour = Posterior chamber

2

Where are the anterior and posterior chambers of the eye?

Anterior to the lens
Ant = in front of iris
Post = behind iris

3

What is the pathway of aqueous humour movement?

Produced in posterior chamber
Passes out and round the iris
Into anterior chamber

4

What might occur as a result of blockage of the aqueous humour pathway?

Increased pressure in anterior an posterior chamber
Glaucoma

5

What might cause raise intracranial pressure?

Head injury
Space occupying lesion, tumour, abscess or haemorrhage
Hydrocephalus
Meningitis

6

What are the three main contents of the cranial cavity?

Brain
Cerebrospinal fluid
Blood

7

What is the Munro-Kellie Hypothesis?

An increase in volume of any of the brain cavity content must lead to a decrease in another (relationship between intracranial components and pressure)

8

If not relieved, what is the result of raised intracranial pressure?

Brain damage

9

What is hydrocephalus?

Water on the brain
CSF volume enlarges, ventricles enlarge, brain matter gives way

10

Why can an infant's brain increase in size with hydrocephalus, whereas an adults cannot?

Sutures in the child's cranial cavity have yet to fuse
Ability for growth and expansion

11

What is the sunset sign in hydrocephalus?

Sight of whites of the eye above the iris

12

What are meninges?

Membranes around the brain

13

What are the three layers surrounding the brain, and the spaces in between them?

Extradural space
DURA MATER
Subdural space
ARACHNOID MATER
Subarachnoid space
PIA MATER

14

What is the composition of the dura mater?

Hard, fibrous membrane
Endoesteal layer (stuck to inside of cranial cavity)
Meningeal layer

15

What is the composition of the arachnoid mater?

Spiders web like composition

16

What is contained in the subarachnoid space?

CSF

17

What is the composition of the pia mater?

Thin layer (one cell thick)
Surrounds brain (follows the gyri and sulci)

18

What is the falx cerebri?

Extension of dura mater
Separates the two cerebral hemispheres

19

What is the tentorium cerebelli?

Extension of dura mater
Separates cerebellum form cerebral hemispheres

20

What is the falx cerebelli?

Extension of dura mater
Separates the two hemispheres of the cerebellum

21

What is the tentorial notch?

Mid brain passes through here

22

What is the infundibulum of hypophysis cerebri?

Stalk of the pituitary

23

What is diaphragma sellae?

Part of dura mater where pituitary sits

24

Where are veins of the brain located?

Subarachnoid space

25

What are the dural venous sinuses?

Spaces between the folds of the dura mater containing venous blood (histologically, NOT veins)

26

What re the components of the lateral ventricles?

Body
Frontal (anterior) horns
Occipital (posterior) horns
Temporal (inferior) horns

27

Where is the third ventricle located?

Between thalami

28

Where is the fourth ventricle located?

Between pons/medulla and cerebellum

29

What connects the lateral ventricles to the third ventricle?

Interventricular foramina

30

What connects the third ventricle to the fourth ventricle?

Cerebral aqueduct

31

What is the route of CSF circulation?

Chroroid plexus (production in all ventricles!)
Two lateral ventricles
Interventricular foramina
Third ventricle
Cerebral aqueduct
Fourth ventricle
Median aperture/two lateral apertures (or central canal of spinal cord)
Subarachnoid space
Arachnoid villi
Superior sagittal sinus
Reabsorption into venous system

32

What visual problems can result form raised intracranial pressure?

Transient blurred vision
Double vision
Loss of vision
Papilloedema
Pupillary changes

33

Compression of which CN may lead to diplopia?

CN III, IV or VI

34

How may diplopia due to raised ICP present?

Will be worse when looking in direction of affected muscle
E.g. compression of CN IV affects superior oblique -> diplopia worse on looking down and out

35

Compression of which CN may lead to a dilated pupil, and how?

CN III
Parasympathetic supply to sphincter pupillae compromised
Unopposed sympathetic stimulation of dilator pupillae

36

What is an early sign of raised intracranial pressure?

Fixed, dilated pupil

37

Why is the optic nerve different to other cranial nerves?

It is an extension of the CNS tract

38

What covers the optic nerve?

Meninges (dura, arachnoid and pia mater)

39

What affect does raised ICP have on the optic nerve?

Raised ICP = raised pressure in subarachnoid space
Transmitted along length of optic nerve
Compresses optic nerve, central artery and vein of retina

40

What are the consequences of raised ICP on the optic nerve?

Papilloedema (bulging/swollen discs)
Transient visual obsurations
Transient flickering
Blurring of vision
Constriction of the visual field
Decreased colour perception

41

What are the possible outcomes of damage to CN III?

Paralysis of somatic motor innervation (4 extra ocular muscles and eyelid)
Paralysis of parasympathetic innervation of sphincter pupillae
Lose/slowness of pupillary light reflex, dilated pupil, ptosis, eye turned inferolaterally

42

What are the possible outcomes of damage to CN IV?

Paralysis of superior oblique (so inferior oblique is unopposed)
Eye cant move inferomedially
Diplopia when looking down

43

What are the possible outcomes of damage to CN VI?

Paralysis of lateral rectus
Eye cannot move laterally in horizontal plane

44

In which ways is CN III susceptible to damage?

Compression
Tentorial herniation

45

In which ways is CN IV susceptible to damage?

Stretching
Compression

46

In which ways is CN VI susceptible to damage?

Stretching