THE CRANIAL SINUSES 



numerous cerebral and cerebellar veins. On account of its 

 proximity to the tympanic (mastoid) antrum, the sinus may 

 become the site of a septic thrombus in inflammatory condi- 

 tions of the antrum, and the infection may spread backwards 

 along the cerebellar veins, ultimately giving rise to a cerebellar 

 abscess. 



The Cavernous Sinuses lie one on each side of the body of 

 the sphenoid in the middle cranial fossa. At its anterior end, 



x 



FIG. 56. Transverse Section through the Cavernous Sinus. 



1. Hypophysis. 



2. Endothelial wall of sinus. 



3. Cavernous sinus. 



4. Internal carotid artery. 



5. Oculo-motor nerve. 



6. Abducent nerve. 



7. Trochlear nerve. 



8. Serous layer of dura mater. 



9. Ophthalmic nerve. 



10. Sphenoidal air-sinus. 



11. Endo-periosteum of skull. 



12. Maxillary nerve. 



each sinus receives the ophthalmic veins, which bring it into 

 communication, indirectly, with the veins of the face. From 

 its posterior end, the superior and inferior petrosal sinuses. 

 pass backwards to join, respectively, the transverse sinus and 

 the internal jugular vein. In addition, each cavernous sinus 

 communicates with the veins of the pterygoid plexus through 

 the foramen ovale and through the foramen of Vesalius, when 

 the latter is present. The pterygoid veins are tributaries of 

 the internal maxillary vein, which receives all the alveolar 

 (dental) and a few pharyngeal veins. In this way the latter 



