Optic canal
Exit foramen · CN II
A short canal in the lesser wing of the sphenoid, medial to the superior orbital fissure, carrying the optic nerve inside its meningeal sheath and the ophthalmic artery from the middle cranial fossa into the orbital apex.
Traced from the start
Detail
- Transmits
- Optic nerve (CN II) with dura, arachnoid and pia; ophthalmic artery (first branch of the internal carotid)
- Bone
- Lesser wing of the sphenoid; the canal is about 1 cm long and fixes the nerve so it cannot move with the globe
When it goes wrong
Frontal head injury transmitting force to the fixed intracanalicular nerve (traumatic optic neuropathy)
Immediate monocular visual loss with a relative afferent pupillary defect and an initially normal fundus
Sphenoid wing meningioma, fibrous dysplasia or Graves orbitopathy crowding the orbital apex (orbital apex syndrome)
Visual loss added to the superior orbital fissure pattern of ophthalmoplegia, ptosis and V1 numbness
Practise this structure
4 questions in the bank tagged Cranial Nerves.
A 52-year-old woman has had two months of numbness over the right forehead, the right upper eyelid and the tip of her nose, with a gritty feeling in the right e…
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A 44-year-old man has had 18 months of worsening hearing on the left with constant ringing in that ear. He still follows conversation in a quiet room but cannot…
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A 58-year-old man has sudden vertigo and a hoarse voice, and chokes when he drinks. The palate elevates to the right and there is no gag response when the left…
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A 27-year-old man was struck on the head at football a week ago. He now sees two images, one above the other, worst when reading or going down stairs. The verti…
Foundations · middle twist