What is cavernous sinus syndrome?

Cavernous sinus syndrome

Cavernous sinus syndrome may arise due to mass effect (e.g. result of a pituitary tumour, infection, inflammation, traumatic or vascular processes) on the structures passing through the cavernous sinus.

[Image source: Gray's anatomy- 40th Edition; page: 430]

Clinical features of cavernous sinus syndrome:

• Ophthalmoplegia (from compression of the oculomotor nerve, trochlear nerve, and abducens nerve)
• Ophthalmic sensory loss (due to compression on the ophthalmic nerve)
• Maxillary sensory loss (from the compression of the maxillary nerve)
• Horner's syndrome (due to the effect on the sympathetic plexus running along the internal carotid artery
• Chemosis
• Proptosis

Additional

From the Taber's Cyclopedic Medical Dictionary 23rd Edition: 

• Ophthalmoplegia: Paralysis of some or all of the ocular muscles.
• Chemosis: Edema of the conjunctiva around the cornea
• Horner's syndrome: A syndrome characterized by contraction of the pupil, partial ptosis of the eyelid, enophthalmos, and sometimes loss of sweating over one side of the face.
• Proptosis: An abnormal protrusion forward of the eyeball, seen in thyroid eye disease and tumours of the orbit.