HYPERTROPHY OF THE BRAIN. 281 



without fear of being misunderstood. We do not know whether the 

 proliferation of the neuroglia is the result of frequently-recurring hyper- 

 semia, or of some other cause. 



Hypertrophy of the brain is occasionally congenital, and then often 

 accompanies dwarfishness ; more frequently it develops after birth, is 

 chiefly limited to childhood, and becomes rarer with advancing years. 

 Hypertrophy of the brain acquired after birth is usually accompanied 

 by rachitis, deficient involution of the thymus gland, and hypertrophy 

 of the lymphatics (Rokitansky). Mental excitement, abuse of liquor, 

 and lead-poisoning, are mentioned as exciting causes of the disease, but 

 it is very doubtful whether they act in this way. 



ANATOMICAL APPEARANCES. The brain, almost exclusively the 

 cerebrum, is larger and heavier than normal. On autopsy, if the top 

 of the skull be removed it is difficult to replace it, because the brain 

 bulges out so, and protrudes between the sawed edges of the bone. The 

 cerebral membranes are very thin and bloodless. We often find no trace 

 of liquid in the subarachnoid space. The convolutions on the surface 

 of the cerebrum are flattened and pressed together ; the sulci between 

 them are scarcely perceptible. The centrum semiovale is unusually 

 large, the ventricles are small on section ; the brain-substance, like the 

 membranes, appears bloodless and dry. Its consistence and elasticity 

 are increased. 



If hypertrophy of the brain develop before closure of the skull, the 

 latter is distended, just as in congenital hydrocephalus. If, on the 

 other hand, it does not begin till the sutures are closed, the cranial 

 wall is often thinned by absorption, and the inner lamella loses its 

 smoothness. More rarely, when the disease increases rapidly, the 

 closed sutures are opened and pressed apart. 



SYMPTOMS AND COURSE. Of course, hypertrophy of the brain has 

 the same influence on the intracranial circulation as any other increase 

 of the contents of the skull has ; hence it is accompanied by extensive 

 symptoms of irritation and of paralysis. And it may readily be un- 

 derstood that these symptoms often do not occur, or only attain a low 

 grade, as long as the sutures of the skull are not closed, and the skull 

 can distend in proportion to the enlargement of the brain. The cir- 

 cumstance that children with hypertrophy of the brain are not always 

 deficient in intellectual development, but are sometimes remarkably 

 sharp and competent in proportion to their physical development, 

 , forms a strong point in diagnosis between hydrocephalus and hyper- 

 trophy of the brain in children with very large heads. Among the 

 symptoms most frequently seen, when there is no enlargement of the 

 head, or when it does not correspond to the increase of the brain, the 

 most important are attacks of epileptiform convulsions. These at 





