70-year-old woman comes to physician complaining of visual loss. Her MRI scan shows an enlarged pituitary gland that lies in sella turcica, immediately posterior and superior to which of the following structures?
## **Core Concept**
The sella turcica is a saddle-shaped depression in the sphenoid bone where the pituitary gland is located. The structures immediately posterior and superior to the sella turcica include the **optic chiasm** and the **third ventricle (diencephalon)**, but most specifically and closely related are the **optic nerves** and **optic chiasm**. The question seems to point towards identifying a structure closely related to the sella turcica.
## **Why the Correct Answer is Right**
The correct answer, , refers to the **optic chiasm**. The optic chiasm is a part of the visual pathway where the optic nerves partially cross. It is anatomically located immediately superior to the pituitary gland in the sella turcica. This structure is clinically significant because an enlarged pituitary gland (such as a pituitary adenoma) can compress the optic chiasm, leading to visual disturbances, including bitemporal hemianopia.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option might refer to a structure not directly related to the posterior and superior aspect of the sella turcica. Without a specific label, it's hard to directly refute, but given the context, it's less likely to be correct compared to the optic chiasm.
- **Option B:** Similarly, without a specific label, it's challenging to address directly. However, structures in this area include the cavernous sinus and the internal carotid arteries, which are lateral to the sella turcica rather than posterior and superior.
- **Option D:** This option would be incorrect for similar reasons as A and B, assuming it does not accurately represent the optic chiasm or another directly related structure.
## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that **enlarged pituitary glands can compress the optic chiasm**, leading to visual field defects, particularly bitemporal hemianopia. This is a classic presentation in cases of pituitary adenomas.
## **Correct Answer: B. Optic Chiasm**