DISEASES OF THE BRAIN. 



tacks seem to occur principally when the one constantly present cause, 

 arterial anaemia, is accompanied by any other, often a very slight one, 

 which suddenly and temporarily greatly increases the anaemia. Head- 

 ache, dizziness, photophobia, general hyperaesthesia, mental irritability, 

 occasional vomiting, and subsequently anaesthesia, general muscular 

 debility, mental hebetude and drowsiness, are much less frequent and 

 far less characteristic of the disease. The malady can only be diag- 

 nosed with an approach to certainty where the skull is enlarged and 

 hydrocephalus can be excluded, while in most cases only a probable 

 diagnosis can be made. The course of hypertrophy of the brain is al- 

 ways chronic. It is doubtful whether it ever ends in recovery. Death 

 results either from the disease itself, generally not from a gradually 

 increasing paralysis, but during a severe attack of convulsions, or else 

 from complication with haemorrhages and inflammatory exudations; 

 as may readily be understood, even when very slight, these are ex- 

 tremely dangerous for such patients. 



We cannot speak of treatment of hypertrophy of the brain, for, 

 even where the disease is recognized, we cannot expect any remedy to 

 remove the existing disturbance. 



CHAPTER XVII. 



ATROPHY OF THE BRAIN. 



ETIOLOGY. We must not term every diminution of the brain-sub- 

 stance, particularly those due to destruction of its tissue and to develop- 

 ment of shrinking cicatricial tissue in the place of the destroyed por- 

 tion, atrophy of the brain. True atrophy of the brain consists rather 

 in a diminution of the size or number of the elements, without any per- 

 ceptible previous destruction of them. 



It is convenient to distinguish two forms of atrophy of the brain. 

 In the first, the so-called agenesis, there is incomplete development ; 

 in the second there is a retrogression, a disappearance of the previous 

 ly well-developed constituents of the brain. 



We pass over those forms of agenesis where the brain is so incom- 

 pletely developed that there is either complete idiocy or that life can- 

 not continue, and turn our attention to the interesting and not very 

 rare form of one-sided atrophy of the brain, occurring during fcetal life 

 and the first years of childhood, in which not only may life continue, 

 but there may be a certain amount of intellectual development. The 

 etiology of monolateral agenesis is obscure. It is probably due to in- 

 flammation of the brain, meninges, or skull, during fcetal life or early 

 childhood. 



