3rd nerve palsy Flashcards
what does the superior branch of the 3rd nerve innervate
and what does the inferior branch of the 3rd nerve innervate
- Superior division innervates
Superior rectus
Levator (LPS) - Inferior division innervates
Medial rectus
Inferior rectus
Inferior oblique
Branch to pupil sphincter
Branch to ciliary muscles (accommodation)
what does the 3rd nerve innervate the branch to pupil sphincter and the branch to ciliary muscles via
ciliary ganglion and short ciliary nerves
list the 4 things that will be seen on an affected eye with a 3rd CN palsy
- 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)
What will happen if there is a complete 3rd nerve palsy?
ptosis and deviation will be out and down. Eye cannot move in, up or down.
The pupil will be large and will not reaction to light
when will you mostly see the hypo deviation in a complete 3rd nerve palsy
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
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
- LR and SO unaffected
- unless has a dual nerve palsy caused by a lesion in the cavernous sinus
which eye movements are full and which are limited with a complete 3rd nerve palsy
Full:
abduction
Limited:
elevation
depression
adduction
what is similar about the aetiology of a 3rd nerve palsy and what differentiates these 2 similarities
causes similar for adults and children
but vary in frequency
what needs to be done if a child is seen with symptoms of a 3rd nerve palsy to rule out any sinister causes
refer as an emergency appointment to the HES if theres a sudden onset of a 3rd nerve palsy, with or without pupil involvement
list 6 acquired causes of a 3rd nerve palsy IN adults
- Compression by (PCA) posterior communicating artery aneurysm
Signs may be evolving e.g. pupil not necessarily fixed at first presentation
Life threatening! A and E 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 tumors
pituitary tumour
3% of px wth 3rd nerve palsy - Inflammation or Infection
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
- if painful and dilated pupil
- refer px to casualty asap
other than a PCA aneurysm being the cause of an acquired 3rd nerve palsy in an adult, which other aetiology involves the pupil
- Trauma
Closed head injury: road traffic accident, kick to head from horse
which aetiology of an acquired 3rd nerve palsy in an adult usually makes full recovery
- Vascular
Diabetic or hypertensive
what is the most common classification of aetiology in children
congenital
what is the 3 congenital causes of a 3rd nerve palsy
- 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)
list the 4 acquired causes of a congenital 3rd nerve palsy
- Closed head trauma
Severe head injury - Tumour / aneurysm
Pituitary tumour - Inflammation
Meningitis - Migraine
Rare / transient
Positive sickle cell trait
what 3 signs can a complete 3rd nerve palsy be classified into
- 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)
what 3 things can an incomplete 3rd nerve palsy divided into
- Superior division
OR
- Inferior division
OR
- Single muscle palsy
IR, SR, MR, IO (rare)
what must a singular incomplete muscle palsy of the inferior rectus be differentiated with
myasthenia gravis
IR palsy is extremely rare and so is more likely to be myasthenia gravis
what 4 questions will you want to ask in your case history when enquiring about a 3rd nerve palsy
onset
symptoms
previous history
general health
list 3 things you will want to ask about when asking about the onset of a 3rd nerve palsy
- Sudden or gradual or congenital
- Ptosis
- Pain / headache which can be severe (likely cause is PcoA aneurysm)
which sort of symptoms will a patient with a 3rd nerve palsy experience
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
when will someone notice an AHP and when will they not notice an AHP and why
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
why do you want to ask a patient about previous history in your case history when enquiring about a 3rd nerve palsy
to wee whether its congenital or due to trauma etc
what can the general health of a patient with a 3rd nerve palsy possibly be
Diabetic or hypertension
i.e. any microvascular risk factors
what is the outcome of a complete ptosis in a congenital 3rd nerve palsy
stimulus deprivation amblyopia & suppression
what is the outcome of a complete ptosis in a acquired 3rd nerve palsy
prevents diplopia ; covers the pupil
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
what is the outcome of a partial ptosis in a congenital 3rd nerve palsy
- may have some binocular potential with AHP or may not have binocular potential at all
- strabismic amblyopia (if eyelid obstructs the pupil)
what is the outcome of a partial ptosis in a acquired 3rd nerve palsy
diplopia therefore need to patch
when will you need to do amblyopia treatment for someone who has a partial ptosis in a congenital 3rd nerve palsy
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)
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
- 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
what can be done when doing a cover test to try and measure the angle of aviation caused by a 3rd nerve palsy
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
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
- 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
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
- 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
how does diabetes and hypertension cause a 3rd nerve palsy and explain why the pupil is spared in this case
- 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
what is seen in ocular motility with someone who has a 3rd nerve palsy
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)
what will be seen in the muscle sequelae in patients with a 3rd nerve palsy
Overaction of contralateral LR, SR, SO and IO
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
- 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
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
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
what exactly causes aberrant regeneration to occur and list 4 features that can be seen
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
list 4 treatment routes of a complete 3rd nerve palsy and how long you will wait to do this
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
why are prisms of limited value for treating a 3rd nerve palsy and when it may only be of value
- Due to the large exotropia and hypotropia
- 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
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
- 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
when will surgical treatment be carried out
Only after 12 months of stable ocular motility to see if the measurements are stable
what is the aim of surgery for a total 3rd nerve palsy and how is it done and why
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
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
- px needs to know its Limited improvement in range of movements but more so ..
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
why does botulinum toxin and prisms have a limited role as treatment for a complete 3rd nerve palsy
due to the fusion incomitancy these patients have / restricted eye movements
list 2 post op surgery issues of a complete 3rd nerve palsy
- 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
what 2 treatment options are there for the ptosis as a cause of a complete 3rd nerve palsy
- Surgery after strabismus surgery completed only ; so the dipliopa will not effect them as much. Also Bells phenomenon needs to be evaluated so the exposure of Keratitis is known
- Ptosis prop. on glasses
but is expensive and often uncomfortable and increase awareness of deviation to others
what needs to be valued before considering ptosis surgery for a 3rd nerve palsy
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
which 2 types of 3rd nerve palsy is a incomplete palsy classified into
- Divisional Palsy
- Single Muscle Palsy
what can a divisional classification of a incomplete 3rd nerve palsy be
- Superior division
SR, LPS - Inferior division
MR, IO, IR and branch to pupil sphincter & ciliary muscle
what can a single muscle palsy classification of a incomplete 3rd nerve palsy be
Medial rectus
Inferior Oblique
Inferior Rectus
an incomplete 3rd nerve palsy is the majority of…
congenital cases
acquired cases of a incomplete 3rd nerve palsy usually result from
diabetes or hypertension
an incomplete 3rd nerve palsy may have a small…
field of BSV
why may prisms be useful in an incomplete 3rd nerve palsy
because of a divisional 3rd nerve palsy or single muscle 3rd nerve palsy
what is the surgical procedure of a incomplete 3rd nerve palsy
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
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
- 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
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
- 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
what can be the 2 possible causes of a superior division 3rd nerve palsy
at superior orbital fissure aetiology: trauma, tumour
what do you need to ddx patients with a single muscle palsy with
- Duane’s retraction syndrome
- Thyroid eye disease
- Browns syndrome
Acquired
- IR palsy – myasthenia gravis
a single muscle palsy is often…
congenital
when is treatment for a single muscle palsy indicated
if condition is symptom producing or cosmetically poor (i.e. is symptomatic with double vision)
what will a cover test of a left IR palsy show
LE: Hypertropia with slight exotropia
what is the AHP of a left IR palsy
tilt unaffected side
turn affected side
chin depression
what will the ocular motility of a left IR palsy show
and its muscle sequelae
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
where will the BSV be displaced with a left IR palsy
Displaced up and to unaffected side
what must you exclude when observing a IR palsy
mechanical restrictions e.g. thyroid eye disease
what is an acquired complete 3rd nerve palsy presumed to be
due to posterior communicating artery aneurysm in absence of trauma until proven otherwise
