3rd nerve palsy - MEH

Question 1

what are the 2 divisions of the 3rd nerve?

Answer 1

super division and inferior division

Question 2

where does the 3rd nerve originate?

Answer 2

oculomotor nucleus

Question 3

which muscles does the superior division innervate?

Answer 3

superior rectus
levator (LPS)

Question 4

which muscles does the inferior division innervate?

Answer 4

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

Question 5

what are the characteristics of 3rd nerve palsy?

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

compression on the nerve from the posterior communicating artery aneurysm

Question 8

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

Answer 8

congential

Question 9

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

Answer 9

• isolated idiopathic
• hereditary (autosomal recessive)
• neurological defect

Question 10

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

Answer 10

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

Question 11

what are the 2 classifications of 3rd nerve palsy?

Answer 11

complete or incomplete

Question 12

what does a complete 3rd nerve palsy mean?

Answer 12

superior AND inferior divisions are affected

Question 13

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

Answer 13

severity of motility

Question 14

is the pupil involved in complete 3rdNP?

Answer 14

may or may not be involved

Question 15

what is an incomplete 3rd NP?

Answer 15

superior OR inferior OR single muscle palsy

Question 16

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

Answer 16

IR, SR, MR, IO (rare)

Question 17

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

Answer 17

congenital or trauma

Question 18

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

Answer 18

diabetic or HTN or hyperlipidemia

Question 19

what are the 2 types of ptosis?

Answer 19

complete or partial

Question 20

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

Answer 20

stimulus deprivation amblyopia and suppression

Question 21

Px having a complete ptosis why is this a postive?

Answer 21

Px will not have dipliopa ; no need to patch it

Question 22

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

Answer 22

may have some binocular potential with AHP
strabismic amblyopia

Question 23

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

Answer 23

if symptomatic - PATCH (due to diplopia)

Question 24

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

Answer 24

XOT (crossed dip or suppressed), hypotropia and intorted

Question 25

why is cover test based on corneal reflections?

Answer 25

px my not be able to fix centrally

Question 26

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

Answer 26

dilated - unreactive to light

Question 27

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

Answer 27

accommodative palsy

Question 28

which type of palsy does pupil sparing occur in?

Answer 28

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

Question 29

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

Answer 29

YES

Question 30

when is there a medical/neuro referral needed?

Answer 30

- if pupil becomes involved/recovery does not happen - <40 years non diabetic

Question 31

what do you see on OM?

Answer 31

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

Question 32

which muscles overact on OM?

Answer 32

overaction of CONTRALATERAL LR, SR, SO and IO

Question 33

which nerve do you need to ensure is intact?

Answer 33

4th

Question 34

how do you assess 4th nerve function?

Answer 34

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

Question 35

what are the main actions of the superior oblique ?

Answer 35

depression on ADDuction

Question 36

what is aberrant regeneration?

Answer 36

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

Question 37

when does AR most commonly occur?

Answer 37

- Aneurysm - Trauma - Tumour (rarely) - Congenital

Question 38

when does Aberrant regeneration not occur?

Answer 38

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

Question 39

clinical characteristics of AR?

Answer 39

- 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

Question 40

which muscles are inappropriately supplied with AR?

Answer 40

IR and LPS

Question 41

what is the management of complete 3rd NP?

Answer 41

urgent referral to HES

Question 42

what is the treatment of complete 3rd NP?

Answer 42

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

Question 43

when do the docs consider surgical intervention?

Answer 43

12 months of stable OM cosmetic reasons

Question 44

what is the surgical intervention of 3rd NP?

Answer 44

centralise the affected eye Large recession LR and resect MR

Question 45

what are the options to treat ptosis?

Answer 45

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

Question 45

what are the types of incomplete 3rd NP?

Answer 45

superior divison inferior division single muscle palsy

Question 46

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

Answer 46

SR LPS

Question 47

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

Answer 47

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

Question 48

which type of 3rd NP are prisms useful in?

Answer 48

incomplete 3rd nerve palsy

Question 49

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

Answer 49

down to unaffected side

Question 50

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

Answer 50

R hypodeviation greatest in dextroelevation overaction LIO and RIR and underaction LSO

Question 51

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

Answer 51

hypotropia

Question 52

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

Answer 52

exotropia little or no vertical deviation

Question 53

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

Answer 53

overaction LLR LSR and LSO

Question 54

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

Answer 54

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

Question 55

what is the most common cause of acquired IR palsy?

Answer 55

myasthenia gravis

Question 56

what are the differential diagnoses of single muscle muscle palsy?

Answer 56

duanes retraction syndrome thyroid eye disease browns sundrome

Question 57

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

Answer 57

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

Question 58

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

Answer 58

compression of PCA (aneurysm)

Question 59

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

Answer 59

urgent referral to HES

Question 60

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

Answer 60

Right HYPOTROPIA

Question 61

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?

Answer 61

incomitant deviation large angle deviation small area of BSV