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Binocular Vision > 3rd nerve palsy - MEH > Flashcards

3rd nerve palsy - MEH Flashcards

1
Q

what are the 2 divisions of the 3rd nerve?

A

super division and inferior division

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2
Q

where does the 3rd nerve originate?

A

oculomotor nucleus

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3
Q

which muscles does the superior division innervate?

A

superior rectus
levator (LPS)

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4
Q

which muscles does the inferior division innervate?

A

Medial rectus
Inferior rectus
Inferior oblique
Branch to pupil sphincter
Branch to ciliary muscles

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5
Q

what are the characteristics of 3rd nerve palsy?

A

-ptosis
- exotropia and hypOtropia
- limited ocular motility (in, up and down)
- dilated pupil
- reduced/absent accommodation

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6
Q

what are the most common causes for acquired 3rd nerve palsy? (8)

A
  • head injuries
  • infection or inflammation
  • recent vaccination
  • migraines
  • brain tumours
  • aneurysms
  • vascular (diabetes or HTN)
  • cholesterol
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7
Q

what is the most common cause of acquired 3rd nerve palsy in adults?

A

compression on the nerve from the posterior communicating artery aneurysm

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8
Q

what is the most common cause of 3rd nerve palsy in children?

A

congential

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9
Q

what are the causes of congenital 3rd nerve palsy in children? (3)

A
  • isolated idiopathic
  • hereditary (autosomal recessive)
  • neurological defect
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10
Q

what are the causes of acquired 3rd nerve palsy in children? (4)

A
  • closed head trauma due to severe head injury
  • tumour/aneurysm (pituitary tumour)
  • inflammation (meningitis)
  • migraine (could be because of a positive sickle cell trait)
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11
Q

what are the 2 classifications of 3rd nerve palsy?

A

complete or incomplete

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12
Q

what does a complete 3rd nerve palsy mean?

A

superior AND inferior divisions are affected

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13
Q

in a complete 3rd NP, what determines if it is total or partial?

A

severity of motility

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14
Q

is the pupil involved in complete 3rdNP?

A

may or may not be involved

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15
Q

what is an incomplete 3rd NP?

A

superior OR inferior OR single muscle palsy

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16
Q

if there is single muscle palsy, which muscles are affected?

A

IR, SR, MR, IO (rare)

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17
Q

what are the key point to ask when taking a case history in regards to PREVIOUS HISTORY?

A

congenital or trauma

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18
Q

what are the key point to ask when taking a case history in regards to GENERAL HEALTH ?

A

diabetic or HTN or hyperlipidemia

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19
Q

what are the 2 types of ptosis?

A

complete or partial

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20
Q

if a px has a complete ptosis (congenital), what other ocular symptoms will they have? (2)

A

stimulus deprivation amblyopia and suppression

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21
Q

Px having a complete ptosis why is this a postive?

A

Px will not have dipliopa ; no need to patch it

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22
Q

if a px has congenital partial ptosis, will they have a BSV and will they have amblyopia?

A

may have some binocular potential with AHP
strabismic amblyopia

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23
Q

what do you need to do if px has an acquired partial ptosis?

A

if symptomatic - PATCH (due to diplopia)

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24
Q

what do you find on cover test with someone with 3rd NP?

A

XOT (crossed dip or suppressed), hypotropia and intorted

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25
Q

why is cover test based on corneal reflections?

A

px my not be able to fix centrally

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26
Q

what happens to the pupils in 3rd NP? (if involved)

A

dilated - unreactive to light

27
Q

if ciliary muscle is affected, what symptoms does the px experience?

A

accommodative palsy

28
Q

which type of palsy does pupil sparing occur in?

A

complete palsy secondary to microvascular disease (diabetes, HTN or cholesterol)

29
Q

is there usually 100% recovery in those with 3rd NP, over 40 years old and have diabetes or HTN?

A

YES

30
Q

when is there a medical/neuro referral needed?

A
  • if pupil becomes involved/recovery does not happen
  • <40 years non diabetic
31
Q

what do you see on OM?

A

Limited adduction, elevation and depression
- Unlikely to find a position of BSV due to degree of incomitance on ocular motility

32
Q

which muscles overact on OM?

A

overaction of CONTRALATERAL LR, SR, SO and IO

33
Q

which nerve do you need to ensure is intact?

A

4th

34
Q

how do you assess 4th nerve function?

A

Make patient abduct the eye and then try to look down.
Look for intorsion (iris landmark or conjunctival vessel) to confirm fourth nerve is intact

35
Q

what are the main actions of the superior oblique ?

A

depression on ADDuction

36
Q

what is aberrant regeneration?

A

Following an acute onset CNP a certain amount “miswiring” can occur as the damaged nerve regenerates

37
Q

when does AR most commonly occur?

A
  • Aneurysm
  • Trauma
  • Tumour (rarely)
  • Congenital
38
Q

when does Aberrant regeneration not occur?

A

in diabetic or hypertensive cases as structural framework of nerve remains intact

39
Q

clinical characteristics of AR?

A
  • Elevation of the upper eyelid on down-gaze or adduction (Pseudo Von-Graefe phenomenon)
  • ADduction of the eye on attempted up-gaze
  • Pupil constriction on attempted adduction +/- down-gaze
  • Retraction of globe on attempted elevation / depression
  • Co-contraction of SR / IR
40
Q

which muscles are inappropriately supplied with AR?

A

IR and LPS

41
Q

what is the management of complete 3rd NP?

A

urgent referral to HES

42
Q

what is the treatment of complete 3rd NP?

A

treat underlying aetiology if possible
occlusion if there is troublesome diplopia
surgical intervention
patching if under 8 (prevent amb)

43
Q

when do the docs consider surgical intervention?

A

12 months of stable OM
cosmetic reasons

44
Q

what is the surgical intervention of 3rd NP?

A

centralise the affected eye

Large recession LR and resect MR

45
Q

what are the options to treat ptosis?

A
  • surgery AFTER strab surgery completed
  • evaluation of bell’s phenomenon before lid procedure - due to risk of exposure keratitis
  • ptosis props on glasses (££££)
45
Q

what are the types of incomplete 3rd NP?

A

superior divison
inferior division
single muscle palsy

46
Q

which muscles are affected in superior division incomplete 3rd nerve palsy?

A

SR
LPS

47
Q

which muscles are affected in inferior divisional incomplete 3rd NP?

A

MR, IO, IR and branch to pupil sphincter & ciliary muscle

48
Q

which type of 3rd NP are prisms useful in?

A

incomplete 3rd nerve palsy

49
Q

which side is BSV displaced to in superior division incomplete 3rd nerve palsy?

A

down to unaffected side

50
Q

what is the OM finding in superior division RE incomplete 3rd NP?

A

R hypodeviation greatest in dextroelevation

overaction LIO and RIR and underaction LSO

51
Q

what are the CT findings in superior division incomplete 3rd NP?

A

hypotropia

52
Q

what are the CT findings in inferior divison incomplete 3rd NP?

A

exotropia
little or no vertical deviation

53
Q

what is the OM finding in inferior division incomplete 3rd NP?

A

overaction LLR LSR and LSO

54
Q

what muscles are affected in inferior division incomplete 3rd NP?

A

RE: IR, MR and IO
dilated pupil
and accommodative palsy if parasympathetic fibres affected

55
Q

what is the most common cause of acquired IR palsy?

A

myasthenia gravis

56
Q

what are the differential diagnoses of single muscle muscle palsy?

A

duanes retraction syndrome
thyroid eye disease
browns sundrome

57
Q

what are the 5 questions to consider when px is presenting with 3rd NP?

A

is it isolated?
pupillary involvement?
aberrant regeneration?
is it painful?
life-threatening?

58
Q

If acquired, what do you ASSUME the origin is until proven otherwise?

A

compression of PCA (aneurysm)

59
Q

what do you do with a px presenting with 3rd NP?

A

urgent referral to HES

60
Q

what is the most common deviation in primary position for a NEW ONSET right 3rd nerve palsy?

A

Right HYPOTROPIA

61
Q

a 55 year old man presents with a sudden onset left 3rd NP.
He is very troubled by constant diplopia. Why would prisms not be offered to him?

A

incomitant deviation
large angle deviation
small area of BSV

62
Q
A
63
Q
A

Binocular Vision (30 decks)

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