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Binocular Vision > 6th Nerve Palsy- MEH > Flashcards

6th Nerve Palsy- MEH Flashcards

1
Q

What is another name for the 6th cranial nerve?

A

Abducens nerve

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2
Q

Where is the 6th nerve nucleus found?

A

Base of the 4th ventricle in the pons (brainstem)

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3
Q

What two types of cells are found in the 6th nerve nucleus?

A

Motor neurones that innervate the ipsilateral lateral recuts
Inter-nuclear neurones that innervate the contralateral medial recuts via MFL

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4
Q

Explain the course that the 6th nerve takes to reach lateral recuts.

A
  • Exits brainstem anteriorly
  • Ascends the Clivus
  • Passes over the apex of the temporal bone
  • Goes through cavernous sinus
  • It enters the orbit vis superior orbital fissure
  • Terminates at the lateral recuts muscles
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5
Q

What is the function of the lateral recuts?

A

Inserts closest to the limbus and abducts

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6
Q

What is the lateral recti’s contralateral synergist?

A

Medial rectus

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7
Q

If there is a leison in the 6th nerve nucleus what issue will they have ?

A

Horizontal palsy on the same side

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8
Q

Fill in the gaps

A
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9
Q

Are congenital or acquired 6th nerve palsies more common?

A

Acquired

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10
Q

What is the cause of congenital 6th nerve palsies?

A
  1. Traumatic birth
  2. transient in newborns- this often resolves its self
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11
Q

What is the eight aetiologies of 6th nerve palsies in ADULTS?

A
  • Microvascular (most common in older people)
  • Vascular causes (aneurysms)
  • Neoplasms (tumours)
  • Trauma
  • Neurological disorder (migraine, MS, raised inter cranial pressure)
  • Iatrogenic
  • Idiopathic
  • Inflammatory
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12
Q

What is the aetiologies of 6th nerve palsies in children?

A
  • Intracranial tumours (most common)
  • Raised intracranial hypertension
  • Idiopathic
  • Trauma
  • Inflammation
  • Post viral
  • Secondary to middle ear disease, drugs
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13
Q

What are some clinical features of unilateral 6th nerve palsy?

A
  • Esotropia which is greater in the distance, px may be binocular at near with esophoria
  • Limitation of abduction on affected side
  • AHP- turned to affected side
  • Field of BSV displaced to unaffected side
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14
Q

What you make sure you cover when taking a history for investigation 6th nerve palsy?

A
  • Onset; is it recent? Or longstanding which could indicate complete palsy
  • GH
  • Age
  • History of head injury
  • Pre existing squint?
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15
Q

What tests would you carry out?

A

CT (with and without AHP)
OM
Hess chart to monitor progression
* looking for lateral face incomitances

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16
Q

What is the muscle sequelae you may see with a 6th nerve palsy px?

A

1) U/a affected LR
2) O/a contralateral synergist MR
3) O/a Ipsilateral synergist MR
4) U/a of contralateral rectus

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17
Q

In newly acquired 6th nerve palsies, which steps would you be likely to see?

A

1 & 2

18
Q

Which steps of muscle sequelae can be seen here of a 6th nerve palsy?

A

1 &2

19
Q

Which steps of muscle sequelae can be seen here of a 6th nerve palsy?

A

1 & 2 & 3

20
Q

Which steps of muscle sequelae can be seen here of a 6th nerve palsy?

A

1,2,3,4

21
Q

What is used to measure field of BSV?

A

An arc perimeter

22
Q

Why is field of BSV useful to measure?

A

Helpful for planning surgery both post and pre op

23
Q

What is a bilateral 6th nerve palsy?

A

Affects both LR—> bilateral abduction deficit which can be symmetrical or asymmetrical
*they may have AHP for BSV

24
Q

How is 6th nerve palsy managed in children?

A

Sometimes the have spontaneous recovery
Encourage AHP, fresnel prism, BTXA to MR, occlusion for amb

25
Q

Why must you refer to a neurologist for children with suspect 6th nerve palsy?

A

To establish the causes + get an MRI

26
Q

How is 6th nerve palsy managed In adults with new onset?

A

Regularly monitored for spontaneous recovery (majority of micro vascular ones resolve with in 12 months)
Some do not though

27
Q

What is the reason microvascular nerve palsies get better before they get worse (you should tell your px this) when receiving treatment?

A

As they have been seeing double, they may have have just been ignoring one. As they recover they images become closer= more noticeable to the px

28
Q

What is conservative management for 6th nerve palsy?

A
  • Occlusion for large angle SOT using a patch or bangerter foil
  • Fresnel prism for smaller deviations
29
Q

At what point would you incorporate a prism into someone’s rx for conservative management of 6th nerve palsy?

A

If they know the px will not recover & they are stable for 6th months with Fresnel prism

30
Q

What is the aim of surgery for 6th nerve palsy?

A

Resolve dipl in PP + provide large area of BSV in PP and depression

31
Q

What does type and degree of surgical management depend on?

A
  • Uni or bi lateral palsy
  • Degree of paresis of LR
  • Size of deviation
32
Q

For smaller deviations an reasonable abductions of a unilateral 6th nerve palsy, what surgery would be done?

A

MR recession and LR resection of affected eye

33
Q

For a complete absence of abduction with a unilateral 6th nerve palsy, what surgery would be done?

A

BTXA to ipsilateral MR to asses abduction

34
Q

With a unilateral 6th nerve palsy and no lateral rectus function what surgery would be carried out?

A

Transposition procedure: SR and IR transposed and sutured into LR
BTXA may be give to MR of affected eye too

35
Q

For px with bilateral 6th nerve palsy, what surgery would be done?

A

Operate one eye at a time (3 mth gap), transposing procedure with BXTA to MR too

36
Q

What are 8 differential diagnoses of 6th nerve palsy?

A
  • Duanes retraction syndrome
  • High myopia
  • Graves Oribitopathy (thyroid eye disease)
  • Orbital trauma
  • Decompensating distance SOP
  • Age-related distance esotropia
  • Spasm of near reflex
  • Myaesthenia Gravis (this is a DD for most conditions)
37
Q

What would a px with age-related esotropia complain of?

A

Intermittent dipl in distance, and not sure of onset

38
Q

What signs would you see with a px with age-related SOT?

A

No/ smaller esophoria deviation at near
Smaller/moderate esotropia at distance
No significant rx
Eye movements concomitant

39
Q

What causes age-related esotorpia?

A

Inferior displacement of horizontal rectus muscle or atrophy on orbit leading to sagging LR

40
Q

How is atrophy on orbit leading to sagging LR managed?

A

Incorporation of prism in glasses

41
Q

Would you like some case scenarios?

A

Look at the slides at the end of the PP for a couple for them

Binocular Vision (30 decks)

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