Double Vision

Question 1

presentation of CN VI palsy

Answer 1

double vision - onset could give a clue to cause
describe seeing two objects side by side

problem is more severe when looking in different directions particularly laterally on the side of the palsy

diplopia will resolve if the patient covers the right or left eye

limitation of outward movement of effected eye, often compensate by turning head

convergent squint, larger when looking into the distance

Question 2

which muscles does CN VI innervate

Answer 2

lateral rectus

Question 3

causes of nerve palsy

Answer 3

microvascular infarct
demyelinating disease
poor blood supply to CN caused by a combination of factors - HTN, DM cholesterol and smoking = microvascular palsy
pressure on nerve - tumour, infections
pressure in blood vessels supplying nerve
inflammation of nerve
aneurysm - often get pain too

CN VI could be a sign of intracranial hypertension but often both eyes

Question 4

management of CN VI palsy

Answer 4

doesn’t require urgent neuroimaging:
unless bilateral swollen optic nerves heads (papilledema) suggests raised ICP
they have other CN palsies
patient is 35 or younger - less likely to have atherosclerotic RF, almost all acquired latter in life

Question 5

management of nerve palsies

Answer 5

all patients need to be seen by an optometrist and ophthalmologist
blood tests and MRI to identify cause
prism fitted into glasses
patches are an option

if patient is left with residual diplopia prisms in glasses can be considered for surgical intervention to realign eyes

Question 6

management and prognosis for CN VI

Answer 6

blood tests and MRI to identify cause
prisms for glasses

if angle of the squint is too large to be corrected with prisms botox injections into medial rectus will reduce the size of the convergent squint and relax the medial rectus stopping it from contracting and shortening, reducing outwards movement of the eye even when lateral rectus recovers its normal function

80% of microvascular lateral rectus palsy’s will recover within 3-6 months, spontaneous recovery is less likely to occur if cause was tumour or a head injury

Question 7

presentation of CN III palsy

Answer 7

new onset horizontal and vertical diplopia
droopy eyelid (ptosis)
eye is divergent and depressed - down and out gaze
pupil dilated
can have headache

palsy = eye down and out with droopy eye lid

Question 8

what does CN III innervate

Answer 8

superior, medial and infection rectus, superior oblique, levator palpbrae superioris

so eye goes down and out and lateral well, everything else restricted

Question 9

what is the likely diagnosis?

double vision on looking up 
sunken eye 
brusing and swelling around eye 
history of trauma to the eye 
loss of sensation below orbit

Answer 9

BLOW OUT TRAUMA

inferior orbital floor fracture, this is the weaker bone and tends to give way first due to raised pressure in the orbit, orbital fat and muscle can become entrapped in the fracture

Right infra orbital paraesthesia might occur as V2 division of trigeminal nerve may be affected meaning sensation is lost below the orbit

Question 10

management of a blow out fracture

Answer 10

urgent referral to max fax surgeon
broad spectrum AB
don’t blow nose - communication with the sinuses may mean bacteria can enter the orbit and cause an orbital infection

Question 11

myasthenia gravis presentation

Answer 11

symptoms come on gradually and appear to be variable
may be no obvious abnormal eye movements on examination
eye lids may appear to progressively droop

variable or progressive weakness of eye lid and ocular muscles

Question 12

driving with double vision

Answer 12

MUST advice not to drive with diplopia
can return after a period of adaptation or if double vision has resolved

• Patients can hold a group 1 licence (cars/personal vehicles) if their double vision is controlled with prisms or if they occlude one eye (with a patch) BUT other eye must have sufficient vision (6/12) and adequate visual fields
• Drivers of HGV lorries (group 2 licence) cant drive with persistent diplopia even after a period of adaptation or patched

Question 13

investigations for suspected myasthenia gravis

Answer 13

blood sample for anti cholinesterase antibodies
CT/MRI brain
edrephonium test: administration of edephonium which is a short term anti cholinesterase agent, results in transient improvement of symptoms
chest imaging - required to detect a thymoma (tumour originating from the thymus) which can be the cause in 10% of patients