Eye and Raised Intracranial Pressure

Question 1

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

Answer 1

Aqueous humour = Anterior to lens

Vitreous humour = Posterior chamber

Question 2

Where are the anterior and posterior chambers of the eye?

Answer 2

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

Question 3

What is the pathway of aqueous humour movement?

Answer 3

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

Question 4

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

Answer 4

Increased pressure in anterior an posterior chamber

Glaucoma

Question 5

What might cause raise intracranial pressure?

Answer 5

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

Question 6

What are the three main contents of the cranial cavity?

Answer 6

Brain
Cerebrospinal fluid
Blood

Question 7

What is the Munro-Kellie Hypothesis?

Answer 7

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

Question 8

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

Answer 8

Brain damage

Question 9

What is hydrocephalus?

Answer 9

Water on the brain

CSF volume enlarges, ventricles enlarge, brain matter gives way

Question 10

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

Answer 10

Sutures in the child’s cranial cavity have yet to fuse

Ability for growth and expansion

Question 11

What is the sunset sign in hydrocephalus?

Answer 11

Sight of whites of the eye above the iris

Question 12

What are meninges?

Answer 12

Membranes around the brain

Question 13

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

Answer 13

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

Question 14

What is the composition of the dura mater?

Answer 14

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

Question 15

What is the composition of the arachnoid mater?

Answer 15

Spiders web like composition

Question 16

What is contained in the subarachnoid space?

Answer 16

CSF

Question 17

What is the composition of the pia mater?

Answer 17

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

Question 18

What is the falx cerebri?

Answer 18

Extension of dura mater

Separates the two cerebral hemispheres

Question 19

What is the tentorium cerebelli?

Answer 19

Extension of dura mater

Separates cerebellum form cerebral hemispheres

Question 20

What is the falx cerebelli?

Answer 20

Extension of dura mater

Separates the two hemispheres of the cerebellum

Question 21

What is the tentorial notch?

Answer 21

Mid brain passes through here

Question 22

What is the infundibulum of hypophysis cerebri?

Answer 22

Stalk of the pituitary

Question 23

What is diaphragma sellae?

Answer 23

Part of dura mater where pituitary sits

Question 24

Where are veins of the brain located?

Answer 24

Subarachnoid space

Question 25

What are the dural venous sinuses?

Answer 25

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

Question 26

What re the components of the lateral ventricles?

Answer 26

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

Question 27

Where is the third ventricle located?

Answer 27

Between thalami

Question 28

Where is the fourth ventricle located?

Answer 28

Between pons/medulla and cerebellum

Question 29

What connects the lateral ventricles to the third ventricle?

Answer 29

Interventricular foramina

Question 30

What connects the third ventricle to the fourth ventricle?

Answer 30

Cerebral aqueduct

Question 31

What is the route of CSF circulation?

Answer 31

``` 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 ```

Question 32

What visual problems can result form raised intracranial pressure?

Answer 32

``` Transient blurred vision Double vision Loss of vision Papilloedema Pupillary changes ```

Question 33

Compression of which CN may lead to diplopia?

Answer 33

CN III, IV or VI

Question 34

How may diplopia due to raised ICP present?

Answer 34

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

Question 35

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

Answer 35

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

Question 36

What is an early sign of raised intracranial pressure?

Answer 36

Fixed, dilated pupil

Question 37

Why is the optic nerve different to other cranial nerves?

Answer 37

It is an extension of the CNS tract

Question 38

What covers the optic nerve?

Answer 38

Meninges (dura, arachnoid and pia mater)

Question 39

What affect does raised ICP have on the optic nerve?

Answer 39

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

Question 40

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

Answer 40

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

Question 41

What are the possible outcomes of damage to CN III?

Answer 41

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

Question 42

What are the possible outcomes of damage to CN IV?

Answer 42

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

Question 43

What are the possible outcomes of damage to CN VI?

Answer 43

Paralysis of lateral rectus | Eye cannot move laterally in horizontal plane

Question 44

In which ways is CN III susceptible to damage?

Answer 44

Compression | Tentorial herniation

Question 45

In which ways is CN IV susceptible to damage?

Answer 45

Stretching | Compression

Question 46

In which ways is CN VI susceptible to damage?

Answer 46

Stretching