| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (YD) Class of 2021, Baylor College of Medicine, Houston, Texas |
| Transcript |
So today we're going to be talking about the MRI sequences that a suprasellar mass would look like. A suprasellar mass comes to ophthalmologists as bitemporal hemianopsia and the most common being pituitary adenoma but it can also present to us as cavernous sinus syndrome because of lateral extension into the cavernous sinus and that means ophthalmoplegia. But let's just take a suprasellar mass that is causing a bitemporal hemianopsia, a very common chiasmal presentation. So as you know the sella turcica is the "Turkish saddle" it houses the pituitary gland, the stalk, the diaphragmatic sellae, and above that is the optic chiasm. So lesions that affect the pituitary gland can grow and come out of the sellar and press on the chiasm. So that is an intrasellar mass with suprasellar extension. The most common cause of an intrasellar mass with a suprasellar extension is the pituitary adenomas because the pituitary tumor starts in the sellar and then grows upward through the diaphragma sellae and becomes a tumor that's pressing the optic chiasm producing the bitemporal hemianopsia. So that's why the appearance radiographically of the pituitary adenomas is like a snowman. It's intrasellar passes through the diaphragma and has a suprasellar component. So a snowman is the radiographic appearance of the pituitary tumor. The pituitary tumor is usually heterogeneous, because the composition of the pituitary adenoma is heterogeneous. Not all the cells are the same, there are hormones, there are fluid, there is all sorts of changes that occur in the pituitary adenomas that are not the same across the entire histopathologic structure of the tumor. And so pituitary adenoma is usually heterogeneous and that means on T1 and T2 and after gadolinium it will be heterogenous. It can be iso-intense, hyper-intense and then gadolinium heterogeneous enhancement. That is a typical radiographic appearance of the pituitary adenoma. In contrast a craniopharyngioma is usually suprasellar. It doesn't arise from the sella because it arose from the suprasellar space and has embryologic origin in the Rathke's cleft. The cells there grow up and press on the chiasm. But because the craniopharyngioma is part cranio and part pharynges it will be heterogeneous in its signal as well and we'll have hyperintensity where the proteinaceous cyst is. It will be cystic and solid so even though it's heterogeneous unlike the pituitary adenoma it will have cystic component and a solid component. And after gadolinium administration there'll be variable enhancement. So cystic, solid, heterogeneous enhancement, predominantly suprasellar: that is the radiographic features on M.R of craniopharyngioma. If however you have a meningioma in arises from the meninges and it has had homogenous enhancement and that little bit of the meninges is called the dural tail. So it will be homogenous, It will be isointense on T1, isointense on T2, but it would be vigorously enhancing and homogeneously enhancing after gadolinium contrast material. There may or may not be the dural tail but it'll be dural-based. It'll be suprasellar, but it can be intrasellar rarely. So suprasellar mass, dural tail, homogeneous enhancement and isointensity on T1 and T2; these are the characteristics of the meningioma. And finally you have glioma. In a kid the glioma is going to be in the optic nerve. So here's the chiasm again, here's the stalk and here's the pituitary. So the lesion is going to be interaxial and it's going to cause enlargement of the optic chiasm. So that the tumor itself is inside of the optic apparatus. So there will be enlargement, if you see enlargement of the nerve, or enlargement of the chiasm, there will be variable T1 and T2 signal intensity and variable enhancement after gadolinium. But the key in differentiating feature is that it's interaxial, intraparenchymal, and inside of the optic chiasm or optic nerve itself. And usually that's a kid. In an adult, a glioma of adult is usually bad, a malignant glioma, a higher-grade glioma like glioblastoma multiforme, or anaplastic astrocytoma. So glioma in kids is usually benign, it's associated with neurofibromatosis type one. in adults more likely be malignant glioma and interaxial intraparenchymal inside the optic nerve or chiasm is the distinguishing feature of the suprasellar glioma. So if you just know these top 4: glioma, pituitary adenoma, craniopharyngioma, and meningioma, those are by far the most common suprasellar mass lesions that we would, accompanied by bitemporal hemianopsia, see an MRIs. |
