THE SUPERIOR CAVAL SYSTEM. 



873 



Where the internal carotid enters the cavernous sinus at the internal orifice of the carotid 

 canal the sinus projects downward around the artery in a funnel-shaped manner, and trom it 

 there arises a close net-work of veins, the carotid plexus or carotid sinus, which completely 

 invests the artery throughout its course through the carotid canal, at the lower opening of 

 which it is continued into one or two veins which open into the internal jugular. 



Practical Considerations. — The cavernous sinus, though less frequently 

 affected with thrombosis than any other large sinus, may become infected from 

 foci apparently far removed, through the extra-orbital communications of the 

 ophthalmic veins (pages 879, 880). Thus, carbuncle of the face, cancrum 

 oris, alveolo-dental periostitis, ulceration of the Schneiderian mucous membrane, 

 empyema of the maxillary antrum, abscess of the frontal sinus, osteomyelitis of 



Fig. 757- 



Eyeball 

 Superior 



ophthalmic vein 

 Inferior 



ophthalmic vein 



Optic nerve 

 Ophthalmic vein 



Anteiior 



cHnoid process- 



Cavernous sinus- 



Inferior 



petrosal sinus 



Superior petrosal 

 sinu; 



Lateral sinui 



Inferior 



cerebral vein 



Occipital sinus 



Lateral sinus- 



Optic nerve 



Circular sinus 

 Cavernous sinus 



Basilar sinus 



Inferior 



petrosal sinus 



Superior 



petrosal smus 



Foramen magnum 

 Tentorium cerebelli 



Inferior cerebral vein 



Inferior longitudinal 

 sinus in cross 

 section 



Lateral sinus 

 Torcular Herophili 



Dural sinuses at base of skull ; falx cerebri and left half of tentorium have been removed. 



the frontal diploic tissue, may each be followed by cavernous sinus thrombosis. 

 In the presence of thrombosis, there are two groups of pressure symptoms (a) 

 venous, causing exophthalmos, oedema of the eyelids and of the corresponding side 

 of the root of the nose, and some chemosis ; (d) nervous, causing ptosis, strabismus, 

 variations in the pupil, pain, etc. 



Arterio-venous aneurism between this sinus and the internal carotid, in addition 

 to similar symptoms of venous obstruction (page 863), often likewise causes paralyses 

 in the distribution of the third, the fourth, and the ophthalmic division of the fifth 

 cranial nerves, which lie in the dura mater on the outer wall of the sinus, and of the 

 sixth nerve, which is in close relation to the internal carotid. 



The bulk of the blood of the contents of the anterior and lower portions of the 

 skull empties into the cavernous sinus; that of the remaining portion, — including the 

 greater part of the cerebrum, the cerebellum, the pons, and the cerebral peduncles 



