Anosmia resulting from the involvement of the olfactory tract is rarely seen with pituitary tumors, at least before transcranial surgery. Its presence suggests another cause for visual loss, most often a subfrontal meningioma extending backward, causing downward pressure on the chiasm and even involvement of the optic nerves. Ocular palsies and involvement of the trigeminal nerve (of which a sensitive indicator of involvement is depression of the corneal reflex) provide presumptive evidence of lateral extension of the tumor into the cavernous sinus, where the nerves may be compressed. As mentioned, this is extremely rare in adenomas, except in apoplexy, but is much more common in meningio-mas of the sinus.
A striking finding with long-standing compression of the oculomotor nerve is elevation of the eyelid on attempted adduction because of aberrant re-innervation of the levator palpebrae superioris by regenerating fibers properly destined for the medial rectus. Because spontaneous occurrence of this sign is commonly seen with meningiomas involving the cavernous isinus and infraclinoid aneurysms of the carotid artery, its presence counts against a diagnosis of a pituitary adenoma.
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