Prepared by:
Dr. James Abrahams

Diagnosis:
Suprasellar Meningioma

Figure 1a	Figure 1b
Figure 1c	Figure 1d

Discussion:

The first and most important issue in assessing lesions of the sellar/supra sellar region, is to determine if the lesion arose from within the sella or from above the sella (supra sellar). Lesions that arise from within the sella will usually enlarge the sella considerably before they extend above the diaphragm sellae and into the supra sellar region. Because of this, sellar lesions often have a "snowman" or "figure eight" appearance (Figure 2), with the base of the snowman being the enlarged sella. In Figure 2, note how large the sella is (arrows) compared to the normal sella in Figure 1a (white arrows). Lesions that arise from above the sella may grow down to the diaphragm sellae and therefore give the appearance that they are contiguous with, and arising from, the pituitary gland. In this situation, however, the sella will not be enlarged and there is often a plane which can be seen between the normal pituitary gland and the lesion (black arrows in Figure 1a). Determining whether the lesion is sellar or supra sellar can be difficult, so it is important to look closely and to establish whether the sella is enlarged or not and whether there is a plane between the lesion and pituitary gland.

Figure 1a (modified)

Figure 2

As for the differential diagnosis, lesions that arise in the sella and extend above the diaphragm sellae are almost always pituitary adenomas as in Figure 2. They enhance with contrast and therefore must be differentiated from an aneurysm. An aneurysm is certainly less likely, but if one does transsphenoidal surgery on what is thought to be a pituitary adenoma and it turns out to be an aneurysm, the results can be devastating. Therefore, one must always be suspicious of an aneurysm! The differential of supra sellar lesions is broader and includes meningiomas which enhance uniformly, as in this case. Craniopharyngiomas tend to be more complex and often have areas of calcification, cysts, and enhancement on CT. On MR they can have areas which are bright on the T1 sequence. Craniopharyngiomas in adults tend to be solid lesions which enhance uniformly and can look like meningiomas. Ectopic germinomas (which occur in the supra sellar region instead of the pineal region) often enhance uniformly and, again, can look like a meningioma. The meningioma, however, often has a broader base with the dura and may have a "dural tail."