Magnetic resonance imaging of the optic nerves and chiasm.

Magnetic resonance imaging (MR) of the optic nerves and chiasm was compared with computed tomography (CT) in 4 healthy volunteers, 4 patients without orbital or chiasmal abnormalities, and 4 patients with tumor (anterior clinoid meningioma in 2, optic nerve glioma in 1, and optic nerve sheath meningioma in 1). MR was found to be effective in demonstrating the optic nerves and related structures, particularly the intracanalicular portion of the nerve which is difficult to see with CT. Best results were achieved with partial saturation recovery (SR) images; inversion recovery (IR) and spin echo (SE) techniques were less successful because of decreased spatial resolution (in the case of SE) as well as difficulty in seeing the anterior clinoid processes. As axial views cannot always distinguish the ethmoid sinus tissue from the optic nerve, it may be necessary to employ both axial and coronal images.