Isolated Third Nerve Palsy
Examination
 Complete the examination routine for eyes or CN as instructed
 Proceed to look for intortion of the affected orbit by tilting the head towards the
involved site or looking for intortion when asking patient to look down and
medially of the affected eye; patient maybe tilting his head voluntary away from
the side of the lesion (implies 4th nerve palsy)
 Rule out
 Thyroid, MG
 Superior orbital syndrome and Cavenous sinus syndrome
 Proceed with
 Neck for LNs
 Examine the upper limbs for Cerebellar, hemiplegia, EPSE and areflexia
 Look dor DM dermopathy
 Request
 Corneal reflex (reduced or absent)
 Visual fields (bitemporal hemianopia)
 Fundoscopy for optic atrophy (MS), DM or hypertensive changes
 Visual acuity
 Blood pressure
 Urine dipstick
 Temperature chart
 Headache or pain
Presentation
Sir, this patient has an isolated right third nerve palsy as evidenced by presence of
 Divergent strabismus involving the right orbit which is in a “down and out”
position
 Complete ptosis/partial ptosis of the right eye
 Dilated pupil which is not reactive to direct light and to accommodation
There is no ptosis or superior rectus palsy of the left eye to suggest a III nerve nuclear
lesion.
There are no associated CN palsies to suggest superior orbital fissure syndrome or
cavernous sinus syndrome. I did not find any associated 4th CN palsy with presence of
intortion on asking the patient to adduct the right eye and look downwards. The 6th
CN is also intact. There is also no paraesthesia of the ophthalmic division of the 5th
CN. Gross VA is also intact.
There are no signs of Graves ophthalmopathy (no conjunctival suffusion and
proptosis or lid edema of the right eye)
There is no evidence of fatiguiability to suggest myasthenia gravis.
On examination of the neck, I did not find any enlarged cervical LNs. There is also no
evidence of hemparesis, cerebellar signs, areflexia or tremors or chorea on
examination of the upper limbs. I also did not notice any diabetic dermopathy.
I would like to complete the examination by:
 Corneal reflex (reduced or absent)
 Visual fields (bitemporal hemianopia)
 Fundoscopy for optic atrophy (MS), DM or hypertensive changes
 Visual acuity
 Blood pressure
 Urine dipstick
 Temperature chart
 Headache or pain
In summary, this patient has an isolated right third nerve palsy. The possible causes
include…
Questions
What is the course and anatomy of the 3rd CN?
 Nuclear portion – at the midbrain
 Fascicular intraparenchymal portion – close to the red nucleus, emerges from
cerebral peduncle
 Fascicular subarachnoid portion – meninges, PCA aneurysm(between the PCA
and internal carotid)
 Fascicular cavernous sinus portion – sella turcica between the petroclinoid
ligament below and interclinoid above
 Fascicular orbital portion – superior orbital fissure
Axons run ipsilateral except those to the (1)superior rectus which is innervated from
the contralateral 3rd nucleus and (2) the levator palpebrae which has innervations from
both nuclei.
Hence, right sided 3rd nerve palsy can have contralateral ptosis which is often milder
than the ipsilateral ptosis; also the ipsilateral superior rectus can still be affected due
to involvement of the contralateral fascicular intraparenchymal midbrain portion of
the left 3rd nerve.
For pupillary reflex and accommodation, it is served by the Edinger-Westphal nucleus
and all axons are ipsilateral.
What are the causes of an isolated 3rd nerve palsy?
 Brainstem
 Infarct, haemorrhage, tumour, abscess, multiple sclerosis
 For nuclear lesions
 Will also have contralateral ptosis and elevation palsy
 May have bilateral 3rd nerve palsies (+/- INO)
 For fascicular midbrain lesions
 Weber’s (+ contralateral hemiplegia) – base of midbrain
 Northnagel (+ contralateral cerebellar) – tectum of midbrain
 Benedikt’s (+ contralateral hemiplegia, contralateral cerebellar and
contralateral tremor, athetosis and chorea) – tegmentum of midbrain, red
nucleus

Peripheral
 Subarachnoid portion- PCA aneurysm, meningitis, infiltrative, others eg
sarcoidosis
 Cavernous sinus lesions- Tumour(pituitary adenoma, meningioma,
cranipharyngioma), cavernous sinus thrombosis, inflammatory (Tolosa-Hunt
syndrome which is a non-caseating granulomatous or non-granulomatous
inflammation within cavernous sinus or superior orbital fissure that is treated
with steroids) and ischaemia from microvascular disease affecting the vasa
nervosa, mononeuritis multiplex
 Orbital- tumor (meningioma, hemangioma), endocrine (thyroid) and
inflammatory(orbital inflammatory pseudotumor ie Tolosa Hunt)
 Mononeuritis multiplex, Miller Fischer and MG

Don’t forget migraines and myasthenia! (emergency – Coning, Giant cell Arteritis
and aneurysm)
How would patient present?
 Diplopia
 Ptosis
 Symptomatic glare from failure of constriction of pupil
 Blurring of vision on attempt to focus of near objects due to loss of accomodation
 Pain in certain etiologies
 Diabetes mellitus
 Tolosa-Hunt syndrome
 PCA aneurysm
 Migraine
What are the causes of a dilated pupil?
 III nerve palsy
 Optic atrophy (direct light and accommodation absent with intact consensual
reflex)
 Holmes Adie Pupil (Myotonic pupil)
o Unilateral
o Slow reaction to bright light and incomplete constriction to convergence
o Young women
o Reduced or absent reflexes
 Mydiatric eye drops
 Sympathetic overactivity
Why does a PCA aneurysm results in pupillary involvement whereas conditions such
as DM or hypertension spares the pupil?
 The pupillary fibres are situated superficially and prone to compression whereas
ischaemic lesions tends to affect the core of the nerve thus sparing the pupillary
fibres
How would you investigate?
 Imaging
o CT, MRI
o Angiogram


Blood test
 Fasting blood glucose, ESR
 TFT and edrophonium
LP
How would you manage?
 Medical 3rd nerve palsy
 Education – watchful waiting and avoid driving, heavy machinery and
climbing high places
 Treat underlying conditions such as DM and hypertension
 Watchful waiting
 Spontaneously recover within 8 weeks
 Symptomatic treatment
 NSAIDs for pain
 If complete ptosis, no need to treat diplopia
 Use eye patch for severe diplopia and a prism Fresnel paste on for mild
diplopia
rd
 Surgical 3 nerve palsy - surgery