ATROPHY OF NERVES. 



From arrest of function, from lesions, pressure, distal, but at times central 

 of lesion. Symptoms : Loss of function advancing to paralysis. Muscle 

 atrophy. Prognosis : in absence of incurable cause, is hopeful. Union of 

 divided ends, restoration of function. Treatment : time, ligature of divided 

 ends. 



This is usually the result of arrest of function. It may be due 

 to transverse section of the nerve, as in surgical neurectomy when 

 the separated peripheral end of the nerve gradually wastes. It 

 may come from contused wounds implicating the nerve and caus- 

 ing destruction of its substance. It may be from tumors or other 

 neoplasms pressing on the trunk of the nerve and preventing the 

 passage of nerve currents. Or, inflammatory effusion may press 

 on the nerve, as happens often to the crural in hsemoglobinuria. 

 Or the pressure may come from enlarged mediastinal glands, or 

 even from the distended posterior aorta under habitual violent 

 exertion so as to permanently incapacitate and atrophy the left re- 

 current laryngeal nerve as in chronic laryngeal paralysis (roaring). 

 Similar wasting occurs in. other nerves under corresponding con- 

 ditions. Atrophy may, however, extend centrally from the peri- 

 pheral end of a nerve when it can no longer remain functionally 

 active. We find an example of this in thfe atrophy of the optic 

 nerve up to the commissure when the eyeball has been excised. 

 A similar condition is often seen in horses in which the integrity 

 of the eye has been completely destroyed in connection with re- 

 curring ophthalmia. 



The sj/tfip iomsa.tte1id3.nt on atrophy of a nerve are those of im- 

 paired functicin gradually advancing to complete paralysis of 

 motion or sensation. In cases of a complete breach of continuity 

 as in section or severe traumatism the entire loss of function 

 necessarily precedes the atrophy. Again, when it comes from 

 destructive changes in the coats and media of the eye', and of the 

 ganglionic cells of the retina, the atrophy of the nerve trunk pro- 

 ceeds simultaneously with the lesions of the organ of vision. 



The diagnosis will in many cases be easy as deduced from the 

 traumatic or surgical lesion. In other cases it may be made with 

 190 



