THEOMBOSIS OF CEEEBEAL SINUSES. 175 



vein which passes out through the aqueductus cochleae without 

 participation of the lateral sinus. The mastoid emissary vein is 

 responsible for the production of mastoid oedema and superficial 

 suppuration, but the oedema may occur as a result of mastoid 

 disease without sinus thrombosis. The posterior condylar veins 

 which pass to the suboccipital and thence to the vertebral veins 

 may become involved, and associated with this the posterior 

 cervical venous plexus which lies at the upper part of the 

 posterior triangle of the neck may be the site of thrombosis. 

 The vertebral vein, by its connection with the lateral sinus 

 through the posterior condylar vein, sometimes affords another 

 path for infection of the lungs, when the internal jugular has 

 been ligatured. Suppurative meningitis and extradural abscess 

 are often associated with thrombosis of the lateral sinus, and 

 infection may also spread from the sinus to the cerebrum or 

 cerebellum, giving rise to abscesses in these structures. The 

 external suture between the squamous and petrous bones lying 

 behind the external auditory meatus affords a track by which 

 inflammation in the ear may spread to the surface and so 

 may save the sinus, but this suture closes in the second year 

 of life. 



Thrombosis of the cavernous sinus is uncommon, although its 

 free venous communications render it liable to infection from 

 many places. Lateral sinus thrombosis caused by ear disease, 

 may spread along the petrosal sinuses to the posterior end of the 

 cavernous sinus. The ophthalmic veins which enter the front 

 of the sinus may carry infection to it from the territories of the 

 angular, facial, or supra-orbital veins. Disease of the nose may 

 extend to the sinus by way of the sphenoidal air cells, or by the 

 medium of the ethmoidal veins which enter the ophthalmic trunk, 

 or of veins in the sphenomaxillary fossa which enter the pterygoid 

 plexus, which in turn communicates freely with the cavernous sinus. 

 Ulcerations of the tonsil and pharynx, retropharyngeal abscesses 

 and nasopharyngeal diphtheria have all occasionally caused 

 cavernous thrombosis ; infection being carried by the veins of 

 the pterygoid plexus, which enter the sinus from below through 



