Cavernous sinus thrombosis.
Thrombosis of the cavernous sinus arises either as an osteo-phlebitis or as a thrombo-phlebitis. In the former case, the thrombus is dependent on disease of the bones related to the sinus—arising more especially as the result of prolonged sphenoidal sinusitis—whilst, in the latter instance, the sinus becomes infected through one of the many vascular communications connecting it with other neighbouring regions. Thus the radicles of the ophthalmic vein, by means of their communication with orbital, ethmoidal, and upper nasal vessels, and their connexion at the inner canthus of the eye with radicles of the angular vein, afford the most ready means of infection. Again, infection may spread from the auditory region along the superior petrosal sinus, and from the tonsillar and pharyngeal regions along the various emissary veins connecting the cavernous sinus on the one hand with the deep cervical vascular system on the other.
The two cavernous sinuses intercommunicate by means of the circular sinus, and consequently thrombosis of the one sinus is liable to involve its fellow. According to Macewen,[57] bilateral trouble occurs in 50 per cent. cases, the infection often spreading from one sinus to the other within twenty-four to thirty-six hours.
Thrombosis of the cavernous sinus is often associated with meningeal infection or brain-abscess.
Symptomatology.
(a) Symptoms dependent on the formation of the thrombus and its extension to neighbouring venous and lymphatic channels.
The presence of the thrombus and its extension into ophthalmic, angular, and retinal veins leads to proptosis, paresis of the ocular muscles, disturbances of vision, and œdema. Proptosis is of rapid development, frequently reaching its maximum within a few hours, the globe being protruded in the downward and outward direction. With respect to ocular palsies, the movements of the globe are greatly restricted with squints, ptosis, and perhaps complete ophthalmoplegia. The pupil may be contracted during the earlier stages, becoming fully dilated and insensitive at a later date. The vision suffers in proportion to the degree of paralysis of ocular muscles and associated retinal hæmorrhages and thrombosis. The veins of the lids, conjunctivæ, and upper part of the face and forehead are engorged, with corresponding œdema of the soft parts. The conjunctivæ may be chemotic.
The spread of the thrombus to the opposite sinus results in the development of bilateral symptoms, whilst the involvement of the petrosal sinus may bring about thrombosis of the lateral and sigmoid sinuses, with corresponding developments.
In other cases the meningeal veins are affected at an early date, in which case the symptoms dependent on the cavernous thrombus are obscured by those resulting from the meningeal infection.