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A 75 year old man reported burning pain behind his right eye for several months. Within the past month, he has also noted the gradual development of a droopy right upper lid. When he lifts the lid, he sees double. Contrast CT of the orbits and brain has been normal.
Where is the lesion?
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You are looking at impaired ocular ductions in all directions in the right eye, together with right upper lid ptosis and a dilated right pupil. Importantly, the patient is reporting
BURNING periocular pain, which is a clue to involvement of the trigeminal nerve. Examiners were not aware that, two years earlier, the patient had undergone excision of a squamous
carcinoma on the ipsilateral brow (did you notice the forehead scar?). High-definition MRI disclosed thickness of the cavernous sinus.
Repeat biopsy of the skin lesion showed perineural involvement by cancer. This patient had perineural spread of cancer via the trigeminal nerve to the cavernous sinus, with
dissemination to the ocular motor cranial nerves via their trigeminal innervation.
Trap: imaging abnormalities are always subtle in these cases, so you must suspect the diagnosis. Whenever multiple ocular motor cranial nerve are simultaneously impaired on one side,
turn your locator to the cavernous sinus or superior orbital fissure. And think perineural spread of cancer when you hear “burning pain!”
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