Double vision Flashcards
What would be suggestive of double vision when looking specifically to one side?
Abducens nerve palsy - CN VI
Innervates the lateral rectus muscle
What are some causes of sixth nerve palsy?
- Demyelinating disease
- Raised intracranial pressire
- Microvascular infarct
- Decompensated squint
What patient factors would warrant further investigations for sixth nerve palsy?
Assuming the cause is microvascular:
- Patient age <35 years
Younger patient are less likely to have atherosclerotic risk factors - Patient has bilateral swollen optic nerves
This is called papilloedema, suggesting raised ICP and warrants urgent neuroimaging to rule out compressive lesions - Patient has other cranial nerve palsies
How does sixth nerve palsy present?
CN VI palsy
- Abducens
- Affects lateral rectus muscle
- Cross-eyed presentation
Causes:
- Vasculitic (DM, HTN)
- Raised intracranial pressure
If patient has raised ICP, their palsy will be bilateral
What are the risk factors for raised intracranial pressure?
- Forty
- Fertile
- Fat
- Female
Why does raised ICP cause sixth nerve palsy?
The CN6 makes a sharp turn behind the pons when traveling to the eye
When intracranial pressure is raised, this area of the nerve is most likely to be affected
Papilloedema will most likely be seen (bilateral swollen optic nerves)
What are the risk factors for a third nerve palsy?
Poor blood supply
- Diabetes
- Hypertension
- Hypercholesterolaemia
- Smoking
Direct pressure
- Tumours
- Aneursym
- Head injuries
- Inflammmation - opthalmoplegic migraine (comes and goes)
What are the signs of a third nerve palsy?
- Sudden onset of a droopy eyelid (ptosis)
- Inability to open eye
- Horizontal and vertical diplopia
- Eye deviated down and out
- Enlarged pupil (Suggests pressure on nerve rather than poor blood supply)
What is the management for third nerve palsy?
- Medical emergency
- Can suggest swelling of posterior communicating artery
- Refer to opthalmology
- If pupil is non-reactive, neuroimaging is needed
- If a serious cause is ruled out, patient can be seen in clinic
- 80% of microvascular third nerve palsies resolve in 3-6 months
- Less likely if palsy caused by aneurysm
- Consider use of prisms if there is some recovery
- After 6-12 months, consider surgery
- Restore area of single vision
- Strengthen the medial rectus muscle
When is neuroimaging required for a third nerve palsy?
Neuroimaging:
- Required if the pupil is nonreactive and enlarged
- Medical emergency
- Suggestive of posterior communicating artery aneurysm
How does a third nerve palsy present?
CN III
- Doesn’t innervate superior oblique or lateral rectus
- Inntervates most of the eye muscles
- Innervates levator muscle of eyelid
- Down and out presentation
- Ptosis
- May have enlarged pupil
Causes
- Vasculitic process (DM, HTN)
- Aneursyms
What is the pathophysiology behind a third nerve palsy?
The third nerve exits the midbrain right next to the posterior communicating artery
This part of the artery is particularly susceptible to berry aneurysms
This can cause a third nerve palsy
- The aneurysm affects the superficial parasympathetics of the nerve, rather than the deep vasculature
- The parasympathetics are responsible for pupil constriction
- This can result in blown pupils
What is the immediate management for a blowout/inferior orbital floor fracture?
- Arrange urgent maxillofacial surgery
- Advise the patient not to blow their nose
(bacteria may otherwise enter the orbit, causing infection) - Prescribe a broad spectrum antibiotic
What additional sign can be seen following an inferior orbital floor fracture?
Infra-orbital parasthesia
- Due to V2 division of the trigeminal nerve being affected
- This causes a loss of sensation below the orbit
How does an inferior orbital floor fracture present?
- History of trauma
- Double vision on upgaze
- Otherwise well
- Otherwise normal vision
- Infra-orbital pain
- Infra-orbital swelling
- Infra-orbital bruising
- Eye is sunken
