178 CLINICAL APPLIED ANATOMY. 



Temporo - sphenoidal and cerebellar abscesses are nearly 

 always caused by suppurative ear disease. Caries of the tegmen 

 tympani or of the tegmen antri may give rise to extradural 

 abscess or subdural abscess in the middle fossa, but the brain 

 membranes often become adherent to the lowest temporo- 

 sphenoidal convolution which lies directly over the tegmina, 

 and a temporo-sphenoidal abscess results. 



Extension of inflammation through the labyrinth to the internal 

 auditory meatus produces similar results in the neighbourhood 

 of this opening. The membranes may become adherent and 

 the front part of the lateral lobe of the cerebellum be found 

 to contain an abscess. But temporo-sphenoidal and cerebellar 

 abscesses may occur without caries or perforation of the bone 

 and without adhesion of the brain membranes. In such cases 

 the veins or the perivascular lymphatics are the tracks along 

 which infection travels. The abscesses in the brain or in the 

 cerebellum may be multiple, as many as three having been 

 found in the temporo-sphenoidal lobe and the same number 

 has been known to occur in the cerebellum. The superior 

 petrosal sinus receives veins from the tympanum and from the 

 temporal lobe, so this sinus may provide the link between the 

 two. The lateral sinus receives veins from the mastoid region 

 and the cerebellum, and may allow the transference of the 

 infective agent from one to the other. It is difficult to conceive 

 that such transference can occur unless the sinuses in question 

 are thrombosed. 



At birth there is a petro-squamous suture in the roof of the 

 tympanum, but this is obliterated in the second year and has 

 no influence in the causation of temporo-sphenoidal abscesses, 

 since these are not met with at this period of life. 



Disease of the nose and of its accessory sinuses may lead to 

 abscess in the frontal lobe of the brain. The cribriform plate 

 of the ethmoid forms a very fragile septum between the brain 

 and the roof of the nose. The frontal air sinuses when of 

 average size extend about an inch upwards in the adult, from 

 the upper orbital margin, and nearly an inch backwards along 



