3rd nerve palsy - MEH Flashcards
what are the 2 divisions of the 3rd nerve?
super division and inferior division
where does the 3rd nerve originate?
oculomotor nucleus
which muscles does the superior division innervate?
superior rectus
levator (LPS)
which muscles does the inferior division innervate?
Medial rectus
Inferior rectus
Inferior oblique
Branch to pupil sphincter
Branch to ciliary muscles
what are the characteristics of 3rd nerve palsy?
-ptosis
- exotropia and hypOtropia
- limited ocular motility (in, up and down)
- dilated pupil
- reduced/absent accommodation
what are the most common causes for acquired 3rd nerve palsy? (8)
- head injuries
- infection or inflammation
- recent vaccination
- migraines
- brain tumours
- aneurysms
- vascular (diabetes or HTN)
- cholesterol
what is the most common cause of acquired 3rd nerve palsy in adults?
compression on the nerve from the posterior communicating artery aneurysm
what is the most common cause of 3rd nerve palsy in children?
congential
what are the causes of congenital 3rd nerve palsy in children? (3)
- isolated idiopathic
- hereditary (autosomal recessive)
- neurological defect
what are the causes of acquired 3rd nerve palsy in children? (4)
- closed head trauma due to severe head injury
- tumour/aneurysm (pituitary tumour)
- inflammation (meningitis)
- migraine (could be because of a positive sickle cell trait)
what are the 2 classifications of 3rd nerve palsy?
complete or incomplete
what does a complete 3rd nerve palsy mean?
superior AND inferior divisions are affected
in a complete 3rd NP, what determines if it is total or partial?
severity of motility
is the pupil involved in complete 3rdNP?
may or may not be involved
what is an incomplete 3rd NP?
superior OR inferior OR single muscle palsy
if there is single muscle palsy, which muscles are affected?
IR, SR, MR, IO (rare)
what are the key point to ask when taking a case history in regards to PREVIOUS HISTORY?
congenital or trauma
what are the key point to ask when taking a case history in regards to GENERAL HEALTH ?
diabetic or HTN or hyperlipidemia
what are the 2 types of ptosis?
complete or partial
if a px has a complete ptosis (congenital), what other ocular symptoms will they have? (2)
stimulus deprivation amblyopia and suppression
Px having a complete ptosis why is this a postive?
Px will not have dipliopa ; no need to patch it
if a px has congenital partial ptosis, will they have a BSV and will they have amblyopia?
may have some binocular potential with AHP
strabismic amblyopia
what do you need to do if px has an acquired partial ptosis?
if symptomatic - PATCH (due to diplopia)
what do you find on cover test with someone with 3rd NP?
XOT (crossed dip or suppressed), hypotropia and intorted
why is cover test based on corneal reflections?
px my not be able to fix centrally
what happens to the pupils in 3rd NP? (if involved)
dilated - unreactive to light
if ciliary muscle is affected, what symptoms does the px experience?
accommodative palsy
which type of palsy does pupil sparing occur in?
complete palsy secondary to microvascular disease (diabetes, HTN or cholesterol)
is there usually 100% recovery in those with 3rd NP, over 40 years old and have diabetes or HTN?
YES
when is there a medical/neuro referral needed?
- if pupil becomes involved/recovery does not happen
- <40 years non diabetic
what do you see on OM?
Limited adduction, elevation and depression
- Unlikely to find a position of BSV due to degree of incomitance on ocular motility
which muscles overact on OM?
overaction of CONTRALATERAL LR, SR, SO and IO
which nerve do you need to ensure is intact?
4th
how do you assess 4th nerve function?
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
what are the main actions of the superior oblique ?
depression on ADDuction
what is aberrant regeneration?
Following an acute onset CNP a certain amount “miswiring” can occur as the damaged nerve regenerates
when does AR most commonly occur?
- Aneurysm
- Trauma
- Tumour (rarely)
- Congenital
when does Aberrant regeneration not occur?
in diabetic or hypertensive cases as structural framework of nerve remains intact
clinical characteristics of AR?
- 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
which muscles are inappropriately supplied with AR?
IR and LPS
what is the management of complete 3rd NP?
urgent referral to HES
what is the treatment of complete 3rd NP?
treat underlying aetiology if possible
occlusion if there is troublesome diplopia
surgical intervention
patching if under 8 (prevent amb)
when do the docs consider surgical intervention?
12 months of stable OM
cosmetic reasons
what is the surgical intervention of 3rd NP?
centralise the affected eye
Large recession LR and resect MR
what are the options to treat ptosis?
- surgery AFTER strab surgery completed
- evaluation of bell’s phenomenon before lid procedure - due to risk of exposure keratitis
- ptosis props on glasses (££££)
what are the types of incomplete 3rd NP?
superior divison
inferior division
single muscle palsy
which muscles are affected in superior division incomplete 3rd nerve palsy?
SR
LPS
which muscles are affected in inferior divisional incomplete 3rd NP?
MR, IO, IR and branch to pupil sphincter & ciliary muscle
which type of 3rd NP are prisms useful in?
incomplete 3rd nerve palsy
which side is BSV displaced to in superior division incomplete 3rd nerve palsy?
down to unaffected side
what is the OM finding in superior division RE incomplete 3rd NP?
R hypodeviation greatest in dextroelevation
overaction LIO and RIR and underaction LSO
what are the CT findings in superior division incomplete 3rd NP?
hypotropia
what are the CT findings in inferior divison incomplete 3rd NP?
exotropia
little or no vertical deviation
what is the OM finding in inferior division incomplete 3rd NP?
overaction LLR LSR and LSO
what muscles are affected in inferior division incomplete 3rd NP?
RE: IR, MR and IO
dilated pupil
and accommodative palsy if parasympathetic fibres affected
what is the most common cause of acquired IR palsy?
myasthenia gravis
what are the differential diagnoses of single muscle muscle palsy?
duanes retraction syndrome
thyroid eye disease
browns sundrome
what are the 5 questions to consider when px is presenting with 3rd NP?
is it isolated?
pupillary involvement?
aberrant regeneration?
is it painful?
life-threatening?
If acquired, what do you ASSUME the origin is until proven otherwise?
compression of PCA (aneurysm)
what do you do with a px presenting with 3rd NP?
urgent referral to HES
what is the most common deviation in primary position for a NEW ONSET right 3rd nerve palsy?
Right HYPOTROPIA
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?
incomitant deviation
large angle deviation
small area of BSV
