780 THE NERVOUS SYSTEM. 



HYPERTROPHY AND ATROPHY OF THE BRAIN. 



True Hypertrophy of the brain is rare, and probably always congeni- 

 tal. An increase in the size of the brain from the proliferation of the 

 neuroglia sometimes occurs in children either before or after birth, less 

 frequently in youth, and very seldom in adults. The white substance of 

 the hemispheres is increased in amount. If it take place before the ossi- 

 fication of the cranium, the bones are separated at the sutures and fon- 



FIG. 516. ATROPHY OF A CIRCUMSCRIBED PORTION OK BRAIN CONVOLUTIONS IN A CHILD. 

 From.a lesion of the corresponding blood-vessels. 



tanels; if after this, the inner table of the skull may be eroded and 

 thinned. When the cranium is opened the dura mater appears tense and 

 anremic, the convolutions of the brain are flattened, the brain substance 

 is firm and anaemic, the ventricles are small, the ganglia and cerebellum 

 are either of normal size or compressed. 



The disease is usually very chronic, and destroys life with symptoms 

 of compression of the brain. There may, however, be acute exacerba- 

 tions. 



Atrophy. This may occur as a senile change, or, in adults, in chronic 

 alcohol, opium, or lead poisoning, in chronic insanity, and in chronic 

 meningitis or from local interference with the circulation. In children 

 who are much reduced by chronic diseases atrophy of the brain may ac- 

 company atrophy of the rest of the body. 



