14a above — a very rarely seen by Digital Subtraction Angiography, but much more commonly with Cone Beam / Flat Panel CT, tiny vessel or vessels arising from the “hypophyseal” segment of the internal carotid artery — a proximal intradural segment also known as supraclinoid, paraophthalmic, etc. See ICA page for details of this semantic disorder.
The artery arises from the medial carotid wall — pituitary is medial to the carotid — and supplies the hypophysis, by definition — the pituitary — usually anterior hypophysis and pituitary stalk. The inferior hypophyseal arteries (from the MHT) are usually much bigger and supply the posterior pituitary.
The “hypophyseal aneurysm” — a medially or inferiorly projecting aneurysm from the hypophyseal segment — is thought to be related to this branch — at least by those who believe that aneurysms must arise from branch points. Aneurysms, of course, don’t care for our opinions, but we are right more often than not.
If you want to see hypophyseal arteries, do some high res DYNA of VASO imaging.
Case courtesy Dr. Eytan Raz — here is a beautiful example of a very dominant superior hypophyseal artery (arrow) supplying the posterior hypophysis (arrowhead), with a correspondingly small inferior hypophyseal contribution from the MHT (dashed arrow)
Cross eye stereo
View from the back — again small inferior hypophyseal, big superior hypophyseal — balance again… See the beautiful vascular ring of the posterior pituitary — the connecting it with the contralateral side
MIP image shows the sella nicely — and helps prove its posterior pituitary
Pure arrowless images — easier to steal…
Of course, there is an aneurysm here — the branch point camp would point out how this larger than usual branch is a setup for aneurysmal formation. Naturally…
Supply of the Hypophysis and Balance
As always neuroangio is about balance. There may be one or more superior hypophyseal arteries. Usually one is visible by cone beam/flat panel CT. Sometimes more than two. Here there are 3. Nicely shown is supply of the stalk (open arrow). There is also likely contribution to the optic chiasm, which is of course very important. The inferior hypophyseal branches (dashed arrow) from the MHT support the posterior pituitary. The ILT is hypoplastic, with lateral branches of the MHT (white arrowhead) heading towards the meckel cave and the recurrent branch along the tentorial edge (black arrowhead) supplying territory normally done by the ILT
The image below is from an Ophthalmic Artery case page. The superior hypophyseal branches supplying the stalk are dashed white arrows. Inside the oval are vessels related to the optic nerve and chiasm — possibly in part supplied by the superior hypophyseal branches also, but not sure.
Axial source data movie — pause and scroll
“Carotid Fenestration” — hypophyseal to PCOM connection
Super case by Dr. Eytan Raz
see that small branch to the anterior hypophysis?
Power of Cone Beam CT imaging
Even the smallest superior hypophyseal arteries can be seen with advanced cone beam CT. Top left is an already high resolution cone beam CT volume rendered image with no apparent Superior Hypophyseal. Windowing to increase sensitivity allows for visualization of a tiny superior hypophyseal (arrow) — top right image. Bottom row are axial (left) and coronal (right) MIP images, showing the same artery, as well as beautifully seen pituitary stalk (dashed arrow)
Superior hypophyseal supply of the Optic Nerve
Important point here — since with increasing visualization of this vessel comes possibility of intervention there. Here is an example of superior hypophyseal artery (arrows) supplying the intracranial and optic canal portions of the nerve (dashed arrows). Any ischemia here (posterior ischemic optic neuropathy) would be quite obvious to the patient. Careful now…