176 CLINICAL APPLIED ANATOMY. 



the foramen lacerum medium, the foramen of Vesalius, if present, 

 and the foramen ovale. Alveolar abscesses, and necroses of the 

 jaw and orbit may have the same result. 



Owing to the serious obstruction to the return of blood from 

 the orbit and the intimate relation of the third, fourth, fifth and 

 sixth nerves to the walls of the sinus, the signs of cavernous 

 thrombosis resemble those of cellulitis of the orbit combined with 

 ophthalmoplegia. The lids are swollen and cedematous, and 

 discoloured, the eye is prominent, and there is much chemosis. 

 At the same time the movements of the eye are restricted 

 or lost, and there is considerable pain in the territory of the 

 supraorbital branch of fifth nerve. 



Since the sinus communicates freely by means of the circular 

 sinus with the cavernous sinus of the opposite side the throm- 

 bosis sooner or later becomes bilateral. As nearly all the veins 

 of the sinus drain into the internal jugular veins, these are the 

 vessels which convey pyaemic infection to the lungs and other 

 parts of the body. Any attempt to exclude the cavernous sinus 

 from the circulation calls for a ligature of the internal jugular, 

 very low in the neck. 



The superior longitudinal sinus is usually affected in marantic 

 thrombosis, but is sometimes thrombosed as the result of fractures 

 and injuries to the vertex of the skull, and rarely as a sequel to 

 lateral sinus disease. There are several reasons why, with 

 failing circulation, thrombosis should appear in this sinus. The 

 blood flow in it is retarded because the stream has to pass back- 

 wards whilst the blood in the veins of the cerebral hemispheres 

 is projected into it in the opposite direction ; again, the blood 

 from the ascending arteries of the cortex is carried on into the 

 sinus by veins which also ascend, and so the flow is not 

 assisted by hydrostatic pressure, and lastly the lacunae laterales 

 form as it were small backwaters in which thrombosis may 

 commence. 



As a rule the symptoms of thrombosis of the superior longi- 

 tudinal sinus are indefinite, but sometimes oedema of the scalp 

 occurs and the veins of the parietal, frontal, and occipital regions 



