Formation or presence of a blood clot (thrombus) in the cavernous sinus of the brain. Infections of the paranasal sinuses and adjacent structures, craniocerebral trauma, and thrombophilia are associated conditions. Clinical manifestations include dysfunction of cranial nerves iii, iv, V, and vi, marked periorbital swelling, chemosis, fever, and visual loss. (From Adams et al., Principles of Neurology, 6th ed, p711)