Question

Does the second cranial nerve pass OVER the hypophysis ?

Answer 1

In short, the answer is no, in normal condition.

To answer this question in detail, we need to know what the second cranial nerve is and what hypophysis is!!

There are 12 cranial nerves that arise directly from the brain. Olfactory & optic, the first 2 arise from the cerebrum, whereas the remaining 10 emerge from the brain stem.

The second cranial nerve is the optic nerve. It connects the eye to the brain and carries the impulses formed by the retina. It is a paired nerve that transmits visual information from the retina to the brain.

The pituitary gland (hypophysis) controls important body functions and the hormonal system. It is a protrusion at the base of the brain and about the size of a pea or cherry, which is why it is called "hypophysis"

The optic nerve is formed by the convergence of axons from the retinal ganglion cells. These cells, in turn, receive impulses from the photoreceptors of the eye (the rods and cones). After its formation, the nerve leaves the bony orbit via the optic canal, a passageway through the sphenoid bone. It enters the cranial cavity, running along the surface of the middle cranial fossa in close proximity but not over to the pituitary gland. And it in normal condition it does not pass over the hypophysis.

The clinical relevance for this is a pituitary adenoma is a tumor of the pituitary gland. Within the middle cranial fossa, the pituitary gland lies in close proximity to the optic chiasm. Enlargement of the pituitary gland can, therefore, affect the functioning of the optic nerve.