Third Nerve Palsies

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

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

Aberrant regeneration

• Typically in longstandingcompressivelesions or trauma (Note: doesnotoccur 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