The eye & raised ICP

Question 1

What is raised ICP?

Answer 1

Increase in pressure within the cranial cavity caused by either an increased pressure in fluid surrounding the brain or an increase in pressure within the brain itself

Question 2

Causes of raised ICP

Answer 2

Brain tumour 
Head injry 
Hydrocephalus (increased fluid around the brain) 
Meningitis 
Stroke

Question 3

What 3 components make up the intracranial volume?

Answer 3

Brain
Blood
CSF

Question 4

Why is increased ICP a serious medical problem?

Answer 4

Cranial cavity is an enclosed rigid space
Can’t cope with increase in pressure - causes damage to tissues, shifts in tissues, herniation and constriction of blood vessels

Question 5

Eye related presentations of raised ICP

Answer 5

Transient blurred vision 
Double vision 
Loss of vision 
Papilloedema 
Pupillary changes

Question 6

What percentage of patients with raised ICP report visual problems?

Answer 6

65-75%

Question 7

What covers the optic nerves?

Answer 7

Dura mater
Arachnoid mater
Sub-arachnoid mater
Pia mater

Question 8

What are meninges?

Answer 8

Protective covering of brain & spinal cord

Question 9

What is the dura mater often called?

Answer 9

Hard/tough mother

Question 10

What supplies the sensory innervation of the dura mater?

Answer 10

CN V

Question 11

What is the arachnoid mater often called?

Answer 11

Spidery mother

Question 12

What is found in the subarachnoid space?

Answer 12

Circulating CSF and blood vessels

Question 13

What is the Pia Mater also know as?

Answer 13

Faithful mother

Question 14

What does the Pia mater adhere to?

Answer 14

The brain (and vessels and nerves entering or leaving)

Question 15

Where is CSF produced?

Answer 15

Choroid plexus of the ventricles

Question 16

Where is CSF reabsorbed?

Answer 16

Dural venous sinuses

Question 17

Where is a lumbar puncture taken to obtain a sample of CSF?

Answer 17

L3/4 or L4/5

Question 18

Where does CSF end?

Answer 18

S2

Question 19

Describe CSF circulation

Answer 19

Choroid plexus produces CSF
CSF passes into lateral ventricle
CSF then passes through intraventricular foramniae into 3rd ventricle
CSF then passes down the cerebral aqueduct (of sylvius) into 4th ventricle
Most CSF passes into subarachnoid space through apertures
Some CSF goes down the central canal of the spinal cord
Rebasorbed from the subarachnoid space via the arachnoid granulations into the drual venous sinuses

Question 20

Why does raised ICP affect the eye?

Answer 20

Compresses optic nerve & the central artery and vein of the retina

Question 21

Visual symptoms of raised ICP

Answer 21

Transient visual obscurations 
Transient flickering 
Blurring of vision 
Constriction of the visual field 
Decreased colour perception

Question 22

What symptoms does compression of CN III cause?

Answer 22

Paralysis of somatic motor innervation (4 extraocular muscles & eyelid)
Paralysis of parasympathetic innervation sphincter
Slow light reflex
Eye tuned inferolaterally

Question 23

Which cranial nerve is particularly susceptible to stretching and compression?

Answer 23

CN IV (long,thin)

Question 24

What is the only nerve that comes out the posterior aspect of the brain?

Answer 24

CN IV

Question 25

Which nerve damage causes diplopia going downstairs?

Answer 25

CN IV

Question 26

Which is the abducent nerve susceptible to damage by stretching?

Answer 26

Long intracranial course

Question 27

What is papilloedema?

Answer 27

Swelling of the disc due to raised ICP

Question 28

What are the parts of a CN II examination?

Answer 28

``` Opthalmoscopy Visual acuity Pupil exam Visual field assessment Colour vision ```

Question 29

Signs of raised ICP on ophthalmoscopy

Answer 29

Bilateral swollen discs | Vessels look toruous and engored

Question 30

Pathophysiology of papilloedema

Answer 30

Subarachnoid space around CN II When ICP rises this transmitted to SAS then onto CN II Causes interuption of axoplasmic flow and venous congestion = swollen discs

Question 31

What happens to the brain in raised ICP?

Answer 31

Brain is squeezed through foramen magnum, brainstem compressed

Question 32

What other conditions can cause disc swelling?

Answer 32

Malignant hypertension

Question 33

What are the functions of the CSF?

Answer 33

``` Maintains stable extracellular environment for the brain Buoyancy Provides echanical protection Waster removal Nutrition ```

Question 34

What is the choroid plexus?

Answer 34

A network f capillaries which filter blood to form CSF

Question 35

What physiological actions lead to increased ICP?

Answer 35

Obstruction to CSF circulation Overproduction of CSF (e.g. by tumour) Inadequate absorption

Question 36

Patient with bilateral disc swelling, normal MRI, Lumbar puncture shows raised CSF opening pressure?

Answer 36

Idiopathic Intracranial Hypertension (IIH)

Question 37

What happens if disc swelling becomes chronic?

Answer 37

Disc swelling subsides Disk become atrophic & pale Loss of visual function Blindness may result