| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AM) Class of 2023, Baylor College of Medicine, Houston, Texas |
| Transcript |
We are talking about craniopharyngioma, and as the name implies, it is both cranio (your head) and pharynx (pharyngioma). And the reason it's a combination of cranio and pharynx is because its embryologic origin is from ectoderm. The diencephalon is going to be projecting down, that's the neuroectoderm piece of the pituitary, and from the bottom is the surface ectoderm. So, there's a stalactite of neuroectoderm heading south and a stalagmite of surface ectoderm heading north. This pouch created by the surface ectoderm is the Rathke. And when the two things meet, that cleft is called the Rathke's cleft and it's a potential space for which cystic fluid can accumulate in this space and make a suprasellar mass. So, the anterior and the posterior portions of the pituitary gland have different embryologic origins. One is from the neuroectoderm from the diencephalon, and one is from the surface ectoderm from the pharynx, leading to the tumor we call craniopharyngioma. And what this means is you can have both cystic and solid components to craniopharyngioma. And because it's a benign lesion and it's a chronic lesion, it can be associated with calcification. So, for suprasellar mass lesions with heterogenous content, we might use both a CT and an MRI to give us complementary information about this cystic lesion. A cystic pituitary adenoma can look very similar to cystic craniopharyngioma, and the presence of calcification would push us towards craniopharyngioma. Now once the suprasellar mass forms, it can occur in children or adults, with two peaks of incidence, even though this is an embryological origin tumor. There are many theories about why older people would get an embryologic tumor, one is metaplasia - change in the histology of the tumor that allows it to become a mass. In patients with a suprasellar lesion, this represents the chiasm, the sella, and the stalk. The pituitary gland lives inside this saddle, called Turkish saddle (sella turcica). A lesion from the pituitary is usually an intracellular mass with suprasellar extension. On coronal imaging, it looks like a snowman because the intracellular mass is growing, pinched in by the diaphragma sella. Once it is free of the diaphragma, the head of the snowman will develop, and the poor chiasm will be worn as a hat. Once the snowman hits the chiasm, he will bend the nasal crossing fibers and cause the typical field defect: bitemporal hemianopsia. Because we're pressing from below when arising from the pituitary gland, usually the bitemporal hemianopsia in the pituitary adenoma is denser superiorly. So, a denser superiorly bitemporal hemianopsia is normally a sign we have a suprasellar mass from an intracellular mass with suprasellar extension, and mostly that's pituitary adenoma. However, if derived from the Rathke cleft or the craniopharyngioma, the tumor is often suprasellar in origin with no intracellular component, and that means we might be pressing from above, which produces the bitemporal hemianopsia that is often denser inferiorly. This is super important information to communicate to our neurosurgical colleagues because if it's a pituitary adenoma, we are way more likely to be able to access the lesion from a transsphenoidal approach. If it's completely upstairs, it's way harder to get to the lesion from below, and so the patient may need a craniotomy. So we'd love to be able to tell the neurosurgeons that we have a bitemporal hemianopsia that's denser inferiorly because we have a cystic and solid component, we recommend a CT scan to look for calcification and that might change the surgical approach-- all derived from that visual field. Craniopharyngioma is one of the most common suprasellar lesions that we see. Pituitary adenoma is the number one, with craniopharyngioma and meningioma are probably number two and number three in my clinic. You need to do a visual field on all of these patients, and what we are looking for a bitemporal hemianopsia denser inferiorly. |
