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Flashcards in The eye & raised ICP Deck (37):
1

What is raised ICP?

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

2

Causes of raised ICP

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

3

What 3 components make up the intracranial volume?

Brain
Blood
CSF

4

Why is increased ICP a serious medical problem?

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

5

Eye related presentations of raised ICP

Transient blurred vision
Double vision
Loss of vision
Papilloedema
Pupillary changes

6

What percentage of patients with raised ICP report visual problems?

65-75%

7

What covers the optic nerves?

Dura mater
Arachnoid mater
Sub-arachnoid mater
Pia mater

8

What are meninges?

Protective covering of brain & spinal cord

9

What is the dura mater often called?

Hard/tough mother

10

What supplies the sensory innervation of the dura mater?

CN V

11

What is the arachnoid mater often called?

Spidery mother

12

What is found in the subarachnoid space?

Circulating CSF and blood vessels

13

What is the Pia Mater also know as?

Faithful mother

14

What does the Pia mater adhere to?

The brain (and vessels and nerves entering or leaving)

15

Where is CSF produced?

Choroid plexus of the ventricles

16

Where is CSF reabsorbed?

Dural venous sinuses

17

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

L3/4 or L4/5

18

Where does CSF end?

S2

19

Describe CSF circulation

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

20

Why does raised ICP affect the eye?

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

21

Visual symptoms of raised ICP

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

22

What symptoms does compression of CN III cause?

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

23

Which cranial nerve is particularly susceptible to stretching and compression?

CN IV (long,thin)

24

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

CN IV

25

Which nerve damage causes diplopia going downstairs?

CN IV

26

Which is the abducent nerve susceptible to damage by stretching?

Long intracranial course

27

What is papilloedema?

Swelling of the disc due to raised ICP

28

What are the parts of a CN II examination?

Opthalmoscopy
Visual acuity
Pupil exam
Visual field assessment
Colour vision

29

Signs of raised ICP on ophthalmoscopy

Bilateral swollen discs
Vessels look toruous and engored

30

Pathophysiology of papilloedema

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

31

What happens to the brain in raised ICP?

Brain is squeezed through foramen magnum, brainstem compressed

32

What other conditions can cause disc swelling?

Malignant hypertension

33

What are the functions of the CSF?

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

34

What is the choroid plexus?

A network f capillaries which filter blood to form CSF

35

What physiological actions lead to increased ICP?

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

36

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

Idiopathic Intracranial Hypertension (IIH)

37

What happens if disc swelling becomes chronic?

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