The medial wall of the orbit is made up of the lamina papyracea of the ethmoid bone, the palatine bone, and more posteriorly the thicker bone of the sphenoid that makes up the apex of the orbit. The degree of pneuma-tization of the sphenoid sinus determines whether the optic nerve indents, or is even dehiscent in, its lateral wall. The same applies to the posterior ethmoid sinuses, which can envelop the optic nerve before it reaches the sphenoid sinus if there is a sphenoeth-moid cell. The inferior-medial strut is made of the maxillary bone, and this is often thick (Fig. 14.42). The a
Fig. 14.40 a Coronal and b sagittal MR images, showing the hypertrophied muscles and proptosis of dysthyroid eye disease.
next area of bony condensation is around the infraorbital nerve in the floor of the orbit and lateral to this the bone is thicker and more difficult to remove (Fig. 14.43).
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