Third Nerve Palsy

The third cranial nerve innovates the following muscles:

• Medial rectus
• Superior Rectus
• Inferior Oblique
• Inferior Rectus
• Levator Palpebrae Superioris (lifts the eyelid)
• Sphincter pupillae (constricts the pupil)
• Ciliary muscles (focuses the eye)

Therefore, a complete palsy of this nerve will result in:

• Limitation in adduction
• Limitation in elevation
• Some limitation in depression
• Ptosis
• A fixed, dilated pupil

Some Causes of a Third Nerve Palsy:

• Microvascular (hypertension or diabetes)
• Trauma
• Compression (tumour or aneurysm)
• Iatrogenic (post-neurosurgery)

‘See also’ below how an Orthoptist would record the eye movements of a right third nerve palsy.