ABSCESS OF THE BEAIN. 177 



are turgid. Epistaxis may be present in childhood and inter- 

 ference with the circulation of the cerebral cortex may induce 

 convulsions or paralysis. In early life the foramen caecum 

 transmits to the sinus a small vein from the nose and this may 

 be the source of the epistaxis. The communication with the 

 sinus of the parietal emissary vein may account for venous 

 congestion and oedema in this part of the scalp. 



ABSCESS OF THE BEAIN. 



The intimate relations of the tympanic cavity and of the 

 mastoid cells to the temporo-sphenoidal lobe of the brain and 

 to the cerebellum account for the frequency with which ear 

 disease is the cause of temporo-sphenoidal and of cerebellar 

 abscesses. In like manner the proximity of the upper part of 

 the nasal cavity and of some of the accessory sinuses of the 

 nose to the frontal lobe of the brain may give rise to frontal 

 abscess when the nasal cavities are diseased. 



Brain abscess may also be a sequel of disease or injury of 

 other bones of the skull, and in such cases the abscess a& a 

 rule lies in close relation to the diseased or injured bone. 

 Sometimes the abscess is in a part of the brain remote from 

 the site of injury, but at the same time in a direct line with 

 it ; such a position appears to be determined by the bruising 

 due to contrecoup. In this way a frontal injury has been 

 known to produce an occipital abscess. 



Blood-borne infection from a distance may also be a cause 

 of cerebral abscess. The focus of such infection is usually in 

 the lung, and the infective agent is carried by the pulmonary 

 veins to the left side of the heart, and thence by the arterial 

 system to the brain. Bronchiectasis, empyema, and sometimes 

 phthisis, produce abscesses in this way. Ulcerative endocarditis 

 occasionally leads to embolic abscesses of the brain, but is 

 more likely to induce haemorrhage or cerebral softening. 

 Brain abscesses may also occur in general pyaemia. Abscesses 

 due to blood-borne infection are usually multiple. 



C.A.A. 12 



