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Binocular vision 2 > 3rd nerve palsy > Flashcards

3rd nerve palsy Flashcards

1
Q

what does the superior branch of the 3rd nerve innervate

and what does the inferior branch of the 3rd nerve innervate

A
  1. Superior division innervates
    Superior rectus
    Levator (LPS)
2. Inferior division innervates
Medial rectus
Inferior rectus
Inferior oblique
Branch to pupil sphincter
Branch to ciliary muscles (accommodation)
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2
Q

what does the 3rd nerve innervate the branch to pupil sphincter and the branch to ciliary muscles via

A

ciliary ganglion and short ciliary nerves

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3
Q

list the 4 things that will be seen on an affected eye with a 3rd CN palsy

A
  • Affected eye is “down and out” (exo, hypo)
  • Limited motility depending on degree of ophthalmoplegia
    only LR and SO muscle functioning (e.g. if total or partial 3rd nerve palsy)
  • Pupil is usually dilated (not always)
  • Accommodation is reduced or absent (if pupil is dilated as a result)
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4
Q

when will you mostly see the hypo deviation in a complete 3rd nerve palsy

A

if you dissociate the eye and try to measure their angle of deviation of that eye (

a large exotropia will always be seen
and should always notice a down and out position of the eye in pp

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5
Q

which are the only 2 muscle unaffected by a 3rd nerve palsy and name a time when it may also be affected along with a 3rd nerve palsy

A
  • LR and SO unaffected

- unless has a dual nerve palsy caused by a lesion in the cavernous sinus

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6
Q

which eye movements are full and which are limited with a complete 3rd nerve palsy

A

Full:
abduction

Limited:
elevation
depression
adduction

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7
Q

what is similar about the aetiology of a 3rd nerve palsy and what differentiates these 2 similarities

A

causes similar for adults and children

but vary in frequency

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8
Q

what needs to be done if a child is seen with symptoms of a 3rd nerve palsy to rule out any sinister causes

A

refer as an emergency appointment to the HES if theres a sudden onset of a 3rd nerve palsy, with or without pupil involvement

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9
Q

list 6 acquired causes of a 3rd nerve palsy is adults

A
  • Compression by (PCA) posterior communicating artery aneursym
    Signs may be evolving e.g. pupil not necessarily fixed at first presentation
    Life threatening! AandE referral ASAP
  • Trauma
    Closed head injury: road traffic accident, kick to head from horse
    Often involves pupil involvement
  • Vascular
    Diabetic or hypertensive, often resolves
    50% undiagnosed cases
  • Undetermined (will never know the cause)
  • Direct damage from adjacent tumours
    pituitary tumour
    13% of px wth 3rd nerve palsy
  • Inflammation or Infection
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10
Q

what sign will show you that the aetiology of an acquired 3rd nerve palsy in an adult it due to a compression by a PCA/posterior communicating artery aneurysm
and what should you do if you see this in practice

A
  • if painful and dilated pupil

- refer px to casualty asap

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11
Q

other than a PCA aneurysm being the cause of an acquired 3rd nerve palsy in an adult, which other aetiology involves the pupil

A
  • Trauma

Closed head injury: road traffic accident, kick to head from horse

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12
Q

which aetiology of an acquired 3rd nerve palsy in an adult usually makes full recovery

A
  • Vascular

Diabetic or hypertensive

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13
Q

what is the most common classification of aetiology in children

A

congenital

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14
Q

what is the 3 congenital causes of a 3rd nerve palsy

A
  • Isolated idiopathic
    Specific cause unknown
    Presumed developmental defect of nucleus or in the nerve pathway
  • Hereditary (autosomal recessive)
  • Neurological defect (which involves other signs and symptoms in the first place)
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15
Q

list the 4 acquired causes of a congenital 3rd nerve palsy

A
  • Closed head trauma
    Severe head injury
  • Tumour / aneurysm
    Pituitary tumour
  • Inflammation
    Meningitis
  • Migraine
    Rare / transient
    Positive sickle cell trait
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16
Q

what 3 signs can a complete 3rd nerve palsy be classified into

A
  • Complete = Superior + inferior division
  • Pupil may or may not be involved
    Depending on aetiology of 3rd nerve palsy
  • Total or partial
    Depending on severity of motility
    (severity of which muscles is affected depends on which muscle it is thats affected and to what degree)
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17
Q

what 3 things can an incomplete 3rd nerve palsy divided into

A
  • Superior division

OR

  • Inferior division

OR

  • Single muscle palsy
    IR, SR, MR, IO (rare)
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18
Q

what must a singular incomplete muscle palsy of the inferior rectus be differentiated with

A

myasthenia gravis

IR palsy is extremely rare and so is more likely to be myasthenia gravis

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19
Q

what 4 questions will you want to ask in your case history when enquiring about a 3rd nerve palsy

A

onset
symptoms
previous history
general health

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20
Q

list 3 things you will want to ask about when asking about the onset of a 3rd nerve palsy

A
  • Sudden or gradual or congenital
  • Ptosis
  • Pain / headache which can be severe (likely cause is PcoA aneurysm)
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21
Q

which sort of symptoms will a patient with a 3rd nerve palsy experience

A

Vary with severity of 3rd nerve involvement

  • Diplopia: vertical +/- horizontal (crossed) usually sudden onset if acquired
    Gradual onset: suppression / diplopia
  • Any change since onset
  • Pupil involvement and AHP
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22
Q

when will someone notice an AHP and when will they not notice an AHP and why

A

Notice AHP: in those with a single muscle affected/palsy, as only one is affected they should have a larger area of BSV.
Those with a complete 3rd nerve palsy will have a small area of BSV due to a large area of incomitancy as a result of the affected EOMs and restricted ocular motility = likely to have an AHP

No AHP: anyone with complete 3rd nerve palsy, pupil involvement and ptosis.
Because of the droopiness of the eyelid, it will obscure the diplopia and the px will see single

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23
Q

why do you want to ask a patient about previous history in your case history when enquiring about a 3rd nerve palsy

A

to wee whether its congenital or due to trauma etc

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24
Q

what can the general health of a patient with a 3rd nerve palsy possibly be

A

Diabetic or hypertension

i.e. any microvascular risk factors

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25
Q

what is the outcome of a complete ptosis in a congenital 3rd nerve palsy

A

stimulus deprivation amblyopia & suppression

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26
Q

what is the outcome of a complete ptosis in a acquired 3rd nerve palsy

A

prevents diplopia

but if the eyelid gets better and the 3rd nerve palsy does recover, as the lid improves the patient will be aware of the diplopia again

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27
Q

what is the outcome of a partial ptosis in a congenital 3rd nerve palsy

A
  • may have some binocular potential with AHP or may not have binocular potential at all
  • strabismic amblyopia (if eyelid obstructs the pupil)
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28
Q

what is the outcome of a partial ptosis in a acquired 3rd nerve palsy

A

diplopia therefore need to patch

29
Q

when will you need to do amblyopia treatment for someone who has a partial ptosis in a congenital 3rd nerve palsy

A

only if the eyelid obstructs the pupil and the visions are unequal (if the visions are equal then no amblyopia treatment needs to be done)

30
Q

what will a cover test reveal about the affected eye from a 3rd nerve palsy
what is the cover test based on for this type of px and why

A
  • exotropia (crossed diplopia or suppression)
  • hypotropia
  • intorted

Patient may not be able to fix centrally with affected eye (when the good eye is covered) so cover test based on corneal reflections and documented whether there is slightly nasal or superior seen in affected eye

31
Q

what can be done when doing a cover test to try and measure the angle of aviation caused by a 3rd nerve palsy

A

do a prism reflection test to try and neutralise the corneal reflections you do see

this is because this patient cannot take up central fixation with the affected eye when the good eye is covered

32
Q

what will be seen if the pupil is affected in the 3rd nerve palsy and how much % of cases of the 3rd nerve palsy is the pupil spared

A
  • it will be dilated
  • non responsive to light
  • accommodative palsy due to affect on ciliary muscle and because pupil is not able to constrict
  • 62-83% cases of total 3rd CNP the pupil is spared
33
Q

list 3 aetiologies of a 3rd nerve palsy that pupil sparing can occur in
and what group of people you should refer who has a 3rd nerve palsy and pupil sparing and why

A
  • Occurs in ischaemia however inflammatory & aneursym are possible
  • > 40 yrs – diabetes or hypertension (i.e. microvascular cause) – usually recovery 100% within 6 months or slightly longer
  • Medical / neurology referral (pupil can start off not being involved but then can become involved)
    if pupil becomes involved / recovery does not happen
34
Q

how does diabetes and hypertension cause a 3rd nerve palsy and explain why the pupil is spared in this case

A
  • It is a occlusive disease of network of small blood vessels supplying the nerve (which will be compressed or compromised)
  • Pupillomotor fibres travel in outer layers of nerve therefore closer to nutrient blood supply enveloping the nerve therefore pupil responses are normal
35
Q

what is seen in ocular motility with someone who has a 3rd nerve palsy

A

Limited adduction, elevation and depression

Unlikely to find a position of BSV due to degree of incomitance on ocular motility
because the field of BSV will be extremely small (thats why prisms aren’t beneficial for these patients)

36
Q

what will be seen in the muscle sequelae in patients with a 3rd nerve palsy

A

Overaction of contralateral LR, SR, SO and IO

37
Q

how do you assess that the 4th nerve is intact in someone who has a 3rd nerve palsy and why do you need to do this

A
  • Main action SO depression on ADDuction
  • Make patient abduct the eye and then try to look down as much as they can (even though px with 3rd nerve palsy won’t be able to depress a lot). Examiner should look for intorsion (iris landmark or conjunctival vessel) to confirm fourth nerve is intact

this is done because:

  • Depression and adduction affected in 3rd nerve need to establish if 4th nerve functioning
  • Establish aetiology and therefore what scan to perform
38
Q

what can happen following an acute onset 3rd nerve palsy

list 4 type of aetiologies that can cause this when the nerve palsy starts to recover

and one type of aetiology that this does not occur after and why

A 
Aberrant Regeneration (AR)
Following an acute onset CNP a certain amount “miswiring” can occur as the damaged nerve regenerates, resulting in bizarre eye movements which do not improve with time or can be corrected with surgery
AR most commonly occurs after: 
Aneurysm
Trauma
Tumour (rarely)
Congenital (not uncommon)

Occurs around ~5 weeks after the 3rd nerve palsy in children and 2-3 months in adults after acute 3rd nerve palsy

Does not occur in diabetic or hypertensive cases, presumably because structural framework of nerve remains intact and recovers fully

39
Q

what exactly causes aberrant regeneration to occur and list 4 features that can be seen

A

The axons retract when damaged and grow forward again they enter wrong myelin tube to supply inappropriate muscles
IR to LPS

One or more of the following may be seen:
- Elevation of the upper eyelid on down-gaze or adduction (Pseudo Von-Graefe phenomenon)

  • Adduction of the eye on attempted up-gaze (the eye does not move entirely up, but adducts as well)
  • Pupil constriction on attempted adduction +/- down-gaze
  • Retraction of globe on attempted elevation / depression
    Co-contraction of SR / IR
40
Q

list 4 treatment routes of a complete 3rd nerve palsy and how long you will wait to do this

A

Mostly hospital eye service

Treat underlying aetiology medically, if possible (to establish the cause in the first place)

Child under 8 years - amblyopia therapy (patching)

  • Stimulus deprivation (ptosis)
  • Strabismic

Occlusion may be necessary for troublesome diplopia during recovery

will wait up to a year to establish whether anything needs to be done. because can take 12 months for a nerve palsy to recover

41
Q

why are prisms of limited value for treating a 3rd nerve palsy and when it may only be of value

A
  • because of the small amount of BSV caused by multiple muscles being affected
  • some role in less incomitant cases e.g. recovering cases, post-operative or isolated muscle under actions
42
Q

list 3 things that you can use as occlusion for the diplopia experienced in a 3rd nerve palsy and why prisms are of little use for this purpose

A
  • occlusion patch
  • bangerter foil
  • occlusive contact lens

Prisms of little use unless palsy is mild because of:

  • Reversal of diplopia in different gazes
  • Large angle
  • Extorted image
43
Q

when will surgical treatment be carried out

A

Only after 9 -12 months of stable ocular motility to see if the measurements are stable

44
Q

what is the aim of surgery for a total 3rd nerve palsy and how is it done and why

A

Aim to operate on and centralise affected eye

Large recession LR and resect MR +/- traction suture

Traction sutures to provide adduction force with an insertion through the SR and IR, along fornices to the medial canthus and brought to the surface through the lid skin and tied to bolsters, left for 6 weeks for px to try to adduct that eye as much as possible before they remove them

45
Q

what is the outcome of surgery for a complete 3rd nerve palsy, therefore what do you need to advise the px

and as well as surgery, what else may a px need and why

A
  • Limited improvement in range of movements
    Often cosmetic reasons as only limited field of BSV possible
    So px needs to be advised that the aim of the surgery is just to centralise the eye in primary position, but the limitations of eye movements will still be there

May need occlusive contact lens as achievable area of BSV so small, hence not useful

46
Q

why does botulinum toxin and prisms have a limited role as treatment for a complete 3rd nerve palsy

A

due to the fusion incomitancy these patients have

47
Q

list 2 post op surgery issues of a complete 3rd nerve palsy

A
  • Diplopia in primary position / traumatic loss of fusion (as a result of having a 3rd nerve palsy in the first place)
  • Gross limitations of ocular movements
    Because surgery induces abduction deficit to prevent reoccurrence of exotropia (due to the large recession of the LR muscle, they usually have some limitations on looking outwards as well)
    Any residual vertical can be operated on later
48
Q

what 2 treatment options are there for the ptosis as a cause of a complete 3rd nerve palsy

A
  • Surgery after strabismus surgery completed
  • Ptosis prop. on glasses
    but is expensive and often uncomfortable and increase awareness of deviation to others
49
Q

what needs to be valued before considering ptosis surgery for a 3rd nerve palsy

A

Evaluation of Bell’s phenomenon before lid procedure - exposure keratitis risk

Need to establish how good the patient’s bell’s phenomenon is provided that their ptosis has recovered

If px has got complete ptosis = got poor bell’s phenomenon
If px has got partial ptosis = then need to establish their bell’s phenomenon

50
Q

which 2 types of 3rd nerve palsy is a incomplete palsy classified into

A
  • Divisional Palsy

- Single Muscle Palsy

51
Q

what can a divisional classification of a incomplete 3rd nerve palsy be

A
  • Superior division
    SR, LPS
  • Inferior division
    MR, IO, IR and branch to pupil sphincter & ciliary muscle
52
Q

what can a single muscle palsy classification of a incomplete 3rd nerve palsy be

A

Medial rectus
Inferior Oblique
Inferior Rectus

53
Q

an incomplete 3rd nerve palsy is the majority of…

A

congenital cases

54
Q

acquired cases of a incomplete 3rd nerve palsy usually result from

A

diabetes or hypertension

55
Q

an incomplete 3rd nerve palsy may have a small…

A

field of BSV

56
Q

why may prisms be useful in an incomplete 3rd nerve palsy

A

because of a divisional 3rd nerve palsy or single muscle 3rd nerve palsy

57
Q

what is the surgical procedure of a incomplete 3rd nerve palsy

A

recess - resect procedure

i.e. exactly the same as a complete 3rd nerve palsy = large recession of LR and resection of MR and traction sutures from SR and IR muscle

58
Q

which muscles are affected in a superior division 3rd nerve palsy of the right eye and what is the outcome
what is revealed in cover test
what is revealed in ocular motility
what is the muscle sequelae

A
  • Right eye: LPS, SR
  • BSV displaced down to unaffected side
    Partial ptosis

CT:
Hypotropia / phoria

OM:
R hypodeviation greatest in dextroelevation

Muscle sequelae:
Overaction LIO & RIR and underaction LSO

59
Q

which muscles are affected in a inferior division 3rd nerve palsy of the left eye and what is the outcome
what is revealed in cover test
what is revealed in muscle sequelae

A
  • Left eye: IR, MR, IO
    Pupil (dilated) may or may not be involved
    Accommodative palsy if parasympathetic fibres still on nerve, may or may not be involved

CT:
Exotropia
Little or no vertical deviation

OM:
Overaction LLR, LSR and LSO

60
Q

what can be the 2 possible causes of a superior division 3rd nerve palsy

A

at superior orbital fissure aetiology: trauma, tumour

61
Q

what do you need to ddx patients with a single muscle palsy with

A
  • Duane’s retraction syndrome
  • Thyroid eye disease
  • Browns syndrome

Acquired
- IR palsy – myasthenia gravis

62
Q

a single muscle palsy is often…

A

congenital

63
Q

when is treatment for a single muscle palsy indicated

A

if condition is symptom producing or cosmetically poor (i.e. is symptomatic with double vision)

64
Q

what will a cover test of a left IR palsy show

A

LE: Hypertropia with slight exotropia

65
Q

what is the AHP of a left IR palsy

A

tilt unaffected side
turn affected side
chin depression

66
Q

what will the ocular motility of a left IR palsy show

and its muscle sequelae

A

A exo pattern

  • increase exo on depression
  • loss of adduction by underacting IR
  • increased abduction by overacting SO

Muscle sequelae:
Overaction RSO and LSR and underaction RIO

67
Q

where will the BSV be displaced with a left IR palsy

A

Displaced up and to unaffected side

68
Q

what must you exclude when observing a IR palsy

A

mechanical restrictions e.g. thyroid eye disease

69
Q

what is an acquired complete 3rd nerve palsy presumed to be

A

due to posterior communicating artery aneurysm in absence of trauma until proven otherwise

Binocular vision 2 (20 decks)

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