Double vision case

Question 1

A patient presents with a droopy right upper lid of sudden onset; when he holds lid up he sees double. What are 5 important questions to ask a patient with double vision?

Answer 1

1. Any associated pain e.g. headache (suggesting PCA aneurysm)
2. Does one of the images go when the eye is closed?
3. Are the images next to each other or one above the other?
4. Any general health problems?
5. Any similar previous episodes?

Question 2

What is meant by binocular diplopia?

Answer 2

Caused by ocular misalignment that resolves when either eye is closed

Question 3

What are the causes of binocular diplopia?

Answer 3

Anything that stops coordinated movement of the two eyes, including paralytic squints due to CN palsies which can have sinister intracranial causes

Question 4

What is monocular diplopia?

Answer 4

• This is double vision that is still present with only one eye open. This is less sinister than binocular diplopia and is often due to problems in ocular media e.g. cataracts.
• Two images are usually not identical, often described as ‘ghosing’ and may be ore thna one additional image

Question 5

What are the causes of monocular diplopia?

Answer 5

Problems in ocular media e.g. cataract

Question 6

What are 3 key differences between monocular and binocular double vision?

Answer 6

1. Monocular is not resolved when one eye is closed; binocular will resolve with one eye shut (as due to misalignment of eyes) while monocular is due to problem in ocular media
2. Images are identical in binocular diplopia, whereas ‘ghosting’ occurs in monocular
3. There may be more than two images in monocular but only two in binocular

Question 7

What are 2 examinations that should be performed in a patient with double vision?

Answer 7

1. General observation: ptosis, resting eye positions, pupil size
2. Extraocular movement assessment

Question 8

What are 3 clinical features on examination (extraocular movements, observation) present in CNIII palsy?

Answer 8

• When patient looking straight ahead (primary position) and lid lifted if ptosis present, affected eye will be down and out
• Extraocular movements will show that affected eye can only move to lateral direction, but cannot move up, down or to right
• Pupil reflexes will shown pupil is fixed and dilated in affected eye

Question 9

What is the anatomical course of the third nerve?

Answer 9

• Emerges from anterior aspect of midbrain, passes inferior to posterior cerebral artery and superior to superior cerebellar artery
• Pierces dura mater and enters lateral aspect of cavernous sinus
• Within cavernous sinus, receives sympathetic branches from internal carotid plexus (travel within sheath but don’t combine)
• Leaves cranial cavity through superior orbital fissure, divides into superior and inferior branches.

Question 10

What does the superior branch of the oculomotor nerve supply?

Answer 10

superior rectus and levator palpebrae superioris muscles

Question 11

What does the inferior branch of the oculomotor nerve supply?

Answer 11

Medial rectus, inferior rectus and inferior oblique muscles

Also supplies pre-ganglionic sympathetic fibres to the ciliary ganglion, which innervates sphincter pupillae and ciliary muscles

Question 12

Why is there a ptosis in CNIII palsy?

Answer 12

• It supplies levator palpebrae superioris muscle that lifts eyelid

Question 13

How can the eye movements be explained in CNIII palsy?

Answer 13

• All extraocular muscles paralysed apart from lateral rectus (which moves eye out- abducens) and superior oblique (which moves eye down when inwardly rotated- trochlear)
• These are unopposed and so eye pulled down and out
• Superior oblique usually pulls eye down but only when eye is rotated inwards
• Since medial rectus cannot pull eye inwards, the superior oblique cannot act to pull the eye down

Question 14

What are the 2 types of oculomotor nerve palsy?

Answer 14

1. Medical/ microvascular: due to diabetes, hypertension or vasculitides e.g. GCA
2. Surgical/ compressive: posterior communicating artery aneurysm (most important to rule out

Question 15

What is one way to differentiate between medical and surgical causes of oculomotor nerve palsy?

Answer 15

Pupil examination: the fibres of the oculomotor nerve that are needed for pupil constriction are superficial fibres.

• Compressive cause (PCA) compresses pial blood vessels on surface of nerve and causes damage to these superficial fibres
• Microvascular cause affects the vasa nervorum and consequent ischaemia affects the trunk of the nerve, with the superficial pupillary fibres spared

Therefore pupil involved (fixed dilated pupil) is more likely to be seen in surgical cause rather than medical (not infallible)

Question 16

What are 3 investigations that are appropriate in suspected oculomotor nerve palsy?

Answer 16

1. Blood tests: glucose, HbA1c, ESR/CRP, vasculitic screen
2. Blood pressure
3. CTA/MRA (angiogram)

Question 17

Why is CTA/MRA preferable to plain CT?

Answer 17

large aneurysms and intracranial blood from subarachnoid haemorrhage will be visible but may miss smaller aneurysms so can’t exclude aneurysm

Question 18

What are the pros and cons of a CT angiogram, and what is an alternative?

Answer 18

CTA is gold standard as will show almost all aneurysms

Risk of complications from contrast agent and requires more technical expertise to perform and interpret

MRA is a less invasive alternative

Question 19

What is the management of a surgical cause of CNIII palsy (i.e. posterior communicating artery aneurysm)?

Answer 19

Neurosurgical management: clipping/gluing/coiling/wrapping berry aneurysm

Question 20

What is the management of a medical cause of CNIII palsy?

Answer 20

• Systemic: manage and BP
• Ophthalmological: do nothing if eyelid has dropped (patches eye), often rises as palsy resolves. if troublesome double vision, alleviate by patching eye or using prisms to bend imge towards deviating eye
  
  • initially stick on (Fresnel) prisms; if helps, incorporate into patinets glasses

Question 21

What will usually happen following medical third nerve palsy?

Answer 21

Ptsos and diplopia will improve as blood supply to nerve improves. Failure to improve or deterioration should call diagnosis into question, prompt re-investigation

Question 22

What are 2 possible treatment options in cases there there is a permanent third nerve palsy?

Answer 22

1. Botulinum toxin injections
2. Squint surgey

Question 23

What do botulinum toxin injections to treat third nerve palsy involve?

Answer 23

Use an electrode-guided needle into the lateral rectus, paralyses muscle and pulls eye back to centre; may resolve diplopia in primary position and prevents contracture of muscle

Question 24

How long does the effect of a botulinum toxin injection for third nerve palsy last and what can be done?

Answer 24

wears off in about 3 months but can be repeated

Question 25

What is a disadvantage of botulinum toxin injections to treat third nerve palsy?

Answer 25

Extraocular movements are abolished so diplopia occurs in all positions other than primary position of gaze

Question 26

After what time point, when does satisfactory treatment of third nerve palsy become challenging and why?

Answer 26

>6 months because so many muscles involved, so little possible ocular movement with only two muscles working

Question 27

How effective is squint surgery for third nerve palsy and what is the aim?

Answer 27

Complex and often unsatsifying; aim is just to have eyes straight when looking straight ahead