Identify the superior oblique muscle and trace it forward to the trochlea, where its tendon is reflected at an angle before inserting into the superior aspect of the eyeball. The trochlea may be damaged during removal of the frontal bone, however, the angle of the intermediate tendon should still be visible. Identify the trochlear nerve (CN IV), which innervates the superior oblique muscle. Next, trace the trochlear nerve from its location in the lateral wall of the cavernous sinus into the orbit via the superior orbital fissure.
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