Diagnosis can be difficult

## Anatomy nuggets

- Nucleus in the midbrain at the level of the superior colliculus
- Bilateral levator innervation
- Contralateral superior rectus innervation
- Ipsilateral innervation to the other EOMs
- Travels through the MLF and lateral to the posterior communicating artery
- Travels in the lateral wall of the cavernous sinus
- Superior and inferior branches enter the orbit within the annulus of Zinn
- Superior branch innervates the superior rectus and levator. Inferior branch does the rest
- Parasympathetic fibres from the Edinger-Westphal nucleus travel with the branch to inferior oblique to the ciliary ganglion then in the short ciliary nerves

## Aetiology

- Aneurysms, classically of the PCoA (most commonly at the junction of the PCoA and the ICA)
- Microvascular ischaemia: typically recover over 4 months
- Tumours
- Trauma
- Demyelination
- Vasculitis including GCA
- Congenital

## Subtypes

- Complete vs partial
- Pupil-sparing or involving
- Nuclear, fascicular or peripheral
    - Nuclear:
      - Unilateral palsy
      - Contralateral superior rectus paresis
      - Bilateral partial ptosis

    - Fascicular: ie. paramedial midbrain lesion eg. infarction of cerebral peduncle with involvement of third nerve fascicle
      - Ipsilateral palsy
      - Contralateral intention tremor, ataxia, anaesthesia (**Benedikt** syndrome)
      - Contralateral hemiparesis (**Weber** syndrome)

- Isolated vs complex (ie. associated with other deficits)

## Clinical features

- Diplopia with horizontal and/or vertical ophthalmoplegia

<HotTopic>
Vertical gaze palsy in third nerve lesions. Doll’s head manoeuvre can distinguish supranuclear from nuclear lesions:

- Eyes elevate on Doll’s head: supranuclear

- Eyes do not elevate on Doll’s head: nuclear

</HotTopic>

- Ptosis: bilateral in nuclear lesions
- Mydriasis
- Pain: may be severe and similar to the headache of a SAH
- Difficulty focussing due to pupil involvement

<HotTopic>
Check superior oblique and lateral rectus in third nerve palsy.

- The eye cannot adduct in third nerve palsies, so to assess function of SO, observe for**intorsion**(its primary action) in abduction and downgaze.

- Lateral rectus function can be assessed via saccadic velocity

</HotTopic>

## Aberrant regeneration

- Typically in longstanding**compressive**lesions or trauma (Note: does**not**occur in vasculopathic lesions)
- Lid-gaze dyskinesia:
    - Lid elevation on adduction (‘inverse Duanes’) or depression (pseudo Von Graefe’s sign)

- Pupil-gaze dyskinesia
    - Pupillary constriction on adduction (pseudo Argyll Robertson) or depression

## Tests
- Urgent neuroimaging with angiography (CTA/MRA)
    - Some would observe a pupil-sparing, non-traumatic palsy especially with vasculopathic risk factors/patient over 40 and undertake imaging if no recovery within 3 months.

- Lumbar puncture
- Assess vascular risk factors
- ESR/CRP if over 50
- Hess chart

## Posterior communicating artery aneurysms

- Rupture in 2/3rd
- If ruptures, 50% mortality

## Brainstem syndromes

- Raymond syndrome: 6th nerve palsy with contralateral hemiparesis
    - Lesion in the mid-pons (ventral pons) affecting 6th nerve fasciculus and corticospinal tract

- Weber syndrome: 3rd nerve equivalent of Raymond syndrome
    - Lesion in the midbrain causing fascicular 3rd nerve palsy and contralateral hemiparesis
    - Weber’s is “weak”

- Claude syndrome: ipsilateral 3rd nerve palsy with contralateral ataxia
    - Lesion in the dorsal midbrain affecting superior cerebellar peduncle and 3rd nerve fasciculus
    - Claude is “cerebellar”

- Benedikt syndrome: ipsilateral 3rd nerve palsy with contralateral ‘rubral’ tremor (slow tremor at rest and with movement)
    - Lesion in the midbrain (red nucleus) affecting the 3rd nerve fascicle and red nucleus

- Nothnagel: ipsilateral 3rd nerve palsy and ipsilateral cerebellar ataxia
    - Localises to midbrain

Diagnosis can be difficult Anatomy nuggets Nucleus in the midbrain at the level of the superior colliculus Bilateral levator innervation Contralateral…

Neuro-ophthalmology

Third Nerve Palsies

Intro

FRCOphth Part 2 Study Notes

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