Knowledge of the anatomy of the anterior clinoid processes is important, as an aerated anterior clinoid process may be a confusing pitfall in modern magnetic resonance (MR) imaging— it may mimic a tumor, an aneurysm, blood or calcium, or an abnormal vessel. This article presents an illustrated review of the MR appearance of the anatomy and diseases of this region.
is a Professor of Radiology at the University of California San
Diego Medical Center, San Diego, CA.
The purpose of this article is to summarize pitfalls in the
interpretation of magnetic resonance (MR) imaging due to aeration
of the anterior or posterior clinoid processes.
In the bygone days of plain-film neuroradiology, careful
examinations of the anterior clinoid processes were of diagnostic
importance. Knowledge of anatomy in this region is still important,
as an aerated anterior clinoid process may be a confusing pitfall
in modern MR imaging; it may mimic a tumor (Figure 1), an aneurysm
(Figures 2 and 3), blood (Figure 4), calcium, or an abnormal
vessel. Less frequently, an aerated dorsum sella or a posterior
clinoid process may cause similar diagnostic confusion (Figures 3
and 4). Figure 5 illustrates a potential pitfall in the
interpretation of a maximum intensity algorithm cerebral angiogram
caused by normal fat in a nonaerated anterior clinoid process.
An aerated clinoid process may also be subject to diseases that
typically occur in other paranasal sinuses, such as mucocoele
(Figure 6), that may cause marked visual loss due to proximity to
the optic nerve and ophthalmic artery.
Endoscopic surgeons need to be aware of the anterior clinoid
process because surgical instruments in an aerated clinoid process
are quite close to the optic nerve and the carotid and ophthalmic