Advanced Oculomotor Nerve Quiz

Q1. What resting eye position is classically associated with a complete oculomotor nerve palsy?

• Down and in
• Up and in
• Down and out
• Straight ahead with isolated miosis

Q2. Why does a complete CN III palsy commonly cause ptosis?

• Paralysis of the superior oblique
• Paralysis of orbicularis oculi
• Loss of corneal sensation
• Paralysis of levator palpebrae superioris

Q3. Why can a compressive CN III lesion produce a dilated pupil?

• Compression selectively stimulates the ciliary ganglion
• Compression denervates the dilator pupillae
• Compression activates the optic nerve and constricts the pupil
• Compression can damage superficial parasympathetic fibers to the sphincter pupillae

Q4. Which aneurysm is classically associated with compression of the oculomotor nerve?

• Facial artery aneurysm
• Posterior communicating artery aneurysm
• Anterior spinal artery aneurysm
• Middle meningeal artery aneurysm

Q5. Why may some ischemic oculomotor neuropathies initially spare the pupil?

• Parasympathetic fibers travel entirely in CN II
• Superficial parasympathetic fibers may be relatively preserved while deeper motor fibers are affected
• Ischemia cannot affect parasympathetic fibers
• The pupil is controlled only by the facial nerve

Q6. Which finding helps distinguish a CN III lesion from an isolated abducens nerve lesion?

• Isolated weakness of the superior oblique
• Loss of facial sensation only
• Ptosis with impaired adduction and possible pupillary involvement
• Isolated inability to abduct the eye

Q7. Why can uncal herniation cause oculomotor nerve dysfunction?

• The nerve can be compressed near the tentorial edge by medial temporal displacement
• The nerve passes through the foramen magnum beside the cerebellar tonsil
• The nerve is attached to the falx cerebri
• The nerve lies inside the lateral ventricle

Q8. Which muscle action is most useful for testing the inferior oblique supplied by CN III?

• Elevation of the abducted eye
• Abduction of the eye
• Elevation of the adducted eye
• Depression of the adducted eye

Q9. Which muscle action is most useful for testing the inferior rectus supplied by CN III?

• Depression of the abducted eye
• Depression of the adducted eye
• Abduction from primary position
• Elevation of the adducted eye

Q10. Which statement best integrates oculomotor nerve anatomy?

• CN III supplies only the lateral rectus and carries no autonomic fibers
• CN III carries somatic motor and preganglionic parasympathetic fibers from the midbrain through the cavernous sinus and superior orbital fissure to orbital targets
• CN III is a purely sensory nerve passing through the optic canal
• CN III arises in the medulla and exits through the jugular foramen