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AY Ophthalmology > The eye & raised ICP > Flashcards

The eye & raised ICP Flashcards

1
Q

What is raised ICP?

A

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

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2
Q

Causes of raised ICP

A 
Brain tumour 
Head injry 
Hydrocephalus (increased fluid around the brain) 
Meningitis 
Stroke
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3
Q

What 3 components make up the intracranial volume?

A

Brain
Blood
CSF

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4
Q

Why is increased ICP a serious medical problem?

A

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

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5
Q

Eye related presentations of raised ICP

A 
Transient blurred vision 
Double vision 
Loss of vision 
Papilloedema 
Pupillary changes
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6
Q

What percentage of patients with raised ICP report visual problems?

A

65-75%

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7
Q

What covers the optic nerves?

A

Dura mater
Arachnoid mater
Sub-arachnoid mater
Pia mater

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8
Q

What are meninges?

A

Protective covering of brain & spinal cord

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9
Q

What is the dura mater often called?

A

Hard/tough mother

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10
Q

What supplies the sensory innervation of the dura mater?

A

CN V

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11
Q

What is the arachnoid mater often called?

A

Spidery mother

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12
Q

What is found in the subarachnoid space?

A

Circulating CSF and blood vessels

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13
Q

What is the Pia Mater also know as?

A

Faithful mother

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14
Q

What does the Pia mater adhere to?

A

The brain (and vessels and nerves entering or leaving)

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15
Q

Where is CSF produced?

A

Choroid plexus of the ventricles

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16
Q

Where is CSF reabsorbed?

A

Dural venous sinuses

17
Q

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

A

L3/4 or L4/5

18
Q

Where does CSF end?

A

S2

19
Q

Describe CSF circulation

A

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
Q

Why does raised ICP affect the eye?

A

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

21
Q

Visual symptoms of raised ICP

A 
Transient visual obscurations 
Transient flickering 
Blurring of vision 
Constriction of the visual field 
Decreased colour perception
22
Q

What symptoms does compression of CN III cause?

A

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

23
Q

Which cranial nerve is particularly susceptible to stretching and compression?

A

CN IV (long,thin)

24
Q

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

A

CN IV

25
Q

Which nerve damage causes diplopia going downstairs?

A

CN IV

26
Q

Which is the abducent nerve susceptible to damage by stretching?

A

Long intracranial course

27
Q

What is papilloedema?

A

Swelling of the disc due to raised ICP

28
Q

What are the parts of a CN II examination?

A 
Opthalmoscopy 
Visual acuity 
Pupil exam 
Visual field assessment 
Colour vision
29
Q

Signs of raised ICP on ophthalmoscopy

A

Bilateral swollen discs

Vessels look toruous and engored

30
Q

Pathophysiology of papilloedema

A

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
Q

What happens to the brain in raised ICP?

A

Brain is squeezed through foramen magnum, brainstem compressed

32
Q

What other conditions can cause disc swelling?

A

Malignant hypertension

33
Q

What are the functions of the CSF?

A 
Maintains stable extracellular environment for the brain 
Buoyancy 
Provides echanical protection 
Waster removal 
Nutrition
34
Q

What is the choroid plexus?

A

A network f capillaries which filter blood to form CSF

35
Q

What physiological actions lead to increased ICP?

A

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

36
Q

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

A

Idiopathic Intracranial Hypertension (IIH)

37
Q

What happens if disc swelling becomes chronic?

A

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

AY Ophthalmology (10 decks)

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